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pjp
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 Posted: Wed Sep 13, 2023 3:42 pm Post subject: Are similar TDP ratings for CPUs comparable? |
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In considering a Ryzen upgrade, I want to avoid the massive cooling solutions that seemed necessary. I arbitrarily decided that 65W was probably what I would choose.
I found this: AMD Athlon 3000G Picasso (Zen+) (2 cores, 4 threads; 5MB cache; TDP 35W).
I was initially intrigued by the 35W, but was surprised at the cache size seeming small, so I checked my old Phenom out of curiosity. According to /proc/cpuinfo, it only has 4x512KB (L2) and apparently 6MB L3 (1). That was a bit surprising.
Back to TDP, that same link (1) lists the TDP for that Phenom at 140W. I don't believe I actually have that processor, but maybe I do. /cpu/procinfo lists it as "AMD Phenom(tm) II X4 965," but I can't find any reference to that without "Black Edition." I would have wagered a small amount of money that I didn't spend the extra to get a Black Edition. On the same page is the Phenom X4 9650 with a TDP of 95W.
The main point being that it seems my current processor likely has a TDP in the 95W to 140W range. And what may seem obvious as my question... how comparable are Zen CPUs 65W or 105W range to that of whatever my Phenom is?
My Phenom's CPU fan and heat sink aren't that notable in size, although for the time they may have seemed large. Zen CPU coolers seem comically large. I do see some Zen CPUs at 105W and 120W, but I don't want fans screaming at me if I start sitting next to it on a regular basis, or even from nearby rooms.
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fedeliallalinea
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| Posted: Wed Sep 13, 2023 4:17 pm Post subject: |
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I cannot make any comment on the processors you mention, but I bought a ryzen 9 7950X with the Noctua NH-D15S cooler and Thermal Grizzly Kryonaut paste, although it's quite large, I can't hear the fan at all.
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pietinger
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| Posted: Wed Sep 13, 2023 4:25 pm Post subject: |
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I have his one: https://www.arctic.de/LF2-420 for an Intel i9-13900k. I can hear the fan when I climb under the desk 
What I very much like is: The manufacturer also equips the pump element with a thermally conductive copper base plate and a 40-millimeter fan for cooling the voltage converters. |
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Syl20
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| Posted: Wed Sep 13, 2023 4:59 pm Post subject: Re: Are similar TDP ratings for CPUs comparable? |
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Some Ryzen CPUs have a TDP as huge as their price (280 W !). Perhaps the coolers are oversized to fit these monsters.
With a TDP of 35 W, a passive cooling could be sufficient, I suppose. |
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NeddySeagoon
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| Posted: Wed Sep 13, 2023 6:25 pm Post subject: |
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pjp,
We reached the maximum power density in silicon many years ago. That's the watts/square millimetre of die area.
As the feature size reduces, you get more bang for your watt. More transistors are packed in the same area but the watts/square millimetre stays constant.
This means that a 10 year old CPU does a lot less per watt than a modern CPU.
If you want low power, choose Zen3 or Zen4 to get the best performance per watt.
Zen+ is already obsolete.
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pjp
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| Posted: Wed Sep 13, 2023 9:16 pm Post subject: |
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| fedeliallalinea wrote: | | I cannot make any comment on the processors you mention, but I bought a ryzen 9 7950X with the Noctua NH-D15S cooler and Thermal Grizzly Kryonaut paste, although it's quite large, I can't hear the fan at all. |
Yeah, that's the "comical" size I mentioned :). I presume that size is required, and that model is listed at 170 W.
| pietinger wrote: | I have his one: https://www.arctic.de/LF2-420 for an Intel i9-13900k. I can hear the fan when I climb under the desk ;-)
What I very much like is: The manufacturer also equips the pump element with a thermally conductive copper base plate and a 40-millimeter fan for cooling the voltage converters. |
The only time I hear mine is if ti is compiling, otherwise it's fairly quiet unless there is no noise or I'm right next to it. The original cooler I had on it I think had a larger fan, but I couldn't find a replacement. I'm pretty sure it was audible when compiling too, but I don't remember it that well.
I'm sure cooling the voltage converters is good, but that means I have another fan to worry about replacing. And I've had to replace multiple fans and have 2 CPU coolers die on me (the original was for a Pentium that did not survive).
| Syl20 wrote: | Some Ryzen CPUs have a TDP as huge as their price (280 W !). Perhaps the coolers are oversized to fit these monsters.
With a TDP of 35 W, a passive cooling could be sufficient, I suppose. |
Yeah, $1k - $6k is never going to happen :) I can't find an easy way to compare cooling for those vs the 100W+ range.
| NeddySeagoon wrote: | pjp,
We reached the maximum power density in silicon many years ago. That's the watts/square millimetre of die area.
As the feature size reduces, you get more bang for your watt. More transistors are packed in the same area but the watts/square millimetre stays constant.
This means that a 10 year old CPU does a lot less per watt than a modern CPU.
If you want low power, choose Zen3 or Zen4 to get the best performance per watt.
Zen+ is already obsolete. |
Zen+ is less obsolete than my Phenom :). Although I don't think I noticed any Zen+ models available.
I understand the efficiency gains and performance per watt, but I was trying to determine if the newer unit at the same TDP could be expected to require approximately the same amount of cooling. What I have for the Phenom isn't bad, so maybe I wouldn't need the very large Ryzen cooler for a 65W or even a 105W Ryzen. Although I guess it would just cool that much better if it wasn't needed. At $100+ each, having a spare is hard to do.
The 35W model I mentioned was only a curiosity. I'd guess it is at least somewhat better than what I currently have, but I have no idea how much. And being that it was ~$40 more than a low-end 65W model, I'm not sure it would be worth the cost of an upgrade.
Zen4 / socket AMD5 is still to costly with CPUs and motherboards both costing multiple hundreds of dollars each. I haven't looked at memory for those.
Zen 3 is probably manageable, I'll just have to figure out what chipsets offer which features.
Wi-Fi seems practically unavoidable. Otherwise I'll only need enough SATA ports for 5 or so HDDs (not SSDs). Unless there's a board that supports a LOT of SATA ports, that means I'll probably need some sort of non-SATA SSD for the OS and probably something in case it dies unexpectedly. Memory seems surprisingly approachable, so that's nice. And then something to render "High Quality Text." Integrated graphics has the appeal of not spending additional money for a GPU that I suspect would be orders of magnitude more than necessary.
My enthusiasm for going through all that only lasts for a limited amount of time, so it'll be a while. And I will wait, because I priced a Ryzen pre-built system that was $3k to start. Mind you that wasn't from any of the big names like Dell or HP, etc. Nevertheless, that's too much by a lot.
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szatox
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| Posted: Thu Sep 14, 2023 12:02 am Post subject: |
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| Quote: | | I was trying to determine if the newer unit at the same TDP could be expected to require approximately the same amount of cooling. |
Yes.
I mean, it is affected by max temperature the CPU is expected to run at, but I think pretty much all CPUs shut down at 100°C, so we could say this one is constant.
Ambient temperature is important too, but it is independent of the CPU itself, so can be ignored when comparing 2 cpus (unless CPU's max temperatures happen to actually differ).
Also, the assumption here is that you actually fully load that CPU. Use cases like not making noise when you're watching a video on otherwise idle machine may be a very different game. Mobile chips, focusing on power efficiency rather than performance should have an edge in this case. Still, 170W is quite a lot; a heatsink beefy enough to keep it safe at full throttle should also be able to cool it without noise when it's not busy. |
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steve_v
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| Posted: Thu Sep 14, 2023 5:11 am Post subject: |
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| pjp wrote: | | I was trying to determine if the newer unit at the same TDP could be expected to require approximately the same amount of cooling. |
Well that is what TDP are supposedly provided for, at least in theory. Whether those numbers are accurate is another matter entirely, but you should at least be able to ballpark spec a cooler based on them, assuming you run the CPU at stock power configuration. Probably worth noting that modern motherboards have a tendency to override those for bigger review/bench numbers, and modern CPU specs tend to lie as well for similar reasons.
Noctua's writeup on TDP may be worth a read.
As for cooler reliability, I don't think I've ever seen an air cooler fail. Fans yes, AIO water cooling units definitely, but if you choose an air cooler that takes a standard fan then all you'd ever need wrt spares is a fan of the appropriate size.
FWIW, I'm running a classic NH-U12A on a mildly overclocked 10900KF and a bit of empirical testing and fag-packet calculation (using CPU-reported power consumption) suggests it can handle around 200W continuous at ~25C ambient. That'd make it quite suitable for your CPU, and noctua's ratings agree.
Personally I'd consider a 120mm tower the breakpoint for "ridiculously huge", and IME it's also the point after which non-standard fan sizes start to become more common.
There are of course cheaper options with comparable performance, I only really went with noctua for the reliability of their fans (also generous warranty and free mounting kits for new CPUs). I hate replacing fans.
Any way you look at it though a CPU cooler is probably a relatively minor expense in the context of an all-new build, and with the way modern CPUs are going the new meta is "performance scales with available cooling" for anything high-end.
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pjp
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| Posted: Thu Sep 14, 2023 5:13 am Post subject: |
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It was definitely an odd question. I guess I should have thought about it more and came from the approach of avoiding the larger coolers.
The primary concern was the full throttle noise levels. It isn't infrequent that I hear my current one when it's compiling, so I wanted to make sure I wasn't going to end up with some data-center noise levels (exaggeration to make the point).
On price alone, 105W would be the highest I'd go -- the Ryzen 7 5800X is tempting, but I'll probably go with something for half its cost.
In theory I've always wanted something passively cooled, but that's never seemed viable given software's ability to consume available hardware resources. If the 35W thing I mentioned was less expensive, I might have considered a couple of those.
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steve_v
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| Posted: Thu Sep 14, 2023 5:25 am Post subject: |
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| pjp wrote: | avoiding the larger coolers.
...
The primary concern was the full throttle noise levels. |
That's an inverse relationship most of the time. Larger coolers (and by extension larger diameter fans) provide more cooling at lower noise levels.
As for passive cooling, it's certainly possible but given the large influence of airflow on heatsink efficiency it also tends to be an extremely expensive proposition for all but the lowest power CPUs.
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Syl20
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| Posted: Thu Sep 14, 2023 7:09 am Post subject: |
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| pjp wrote: | | In theory I've always wanted something passively cooled, but that's never seemed viable given software's ability to consume available hardware resources. If the 35W thing I mentioned was less expensive, I might have considered a couple of those. |
So you want something more powerful, more energy-efficient, and cheap (how much, by the way ?). You actual CPU is 14 years old, and known to be quite powerful at that time, but not for its temperance, far from it.
Did you consider second-hand hardware ? It's easy to find a more modern and efficient CPU between 2009 and now.
Depending on your MB, the cheapest upgrade should be a Phenom II X6 1065T.
Otherwise, perhaps you should have a look on Intel products, known to be less burning for the same performance. And the price should not be a problem, if the CPU is sufficiently old : Core I5 4570, or Core I7 4770, for example, are safe bets, for the tenth of the price of the Zen+ you mentioned. And if you want more, the next generations are not really more expensive...
Add a low-profile cooler if you don't have the room for a fridge, and you'll be the happiest user in the world. |
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Anon-E-moose
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| Posted: Thu Sep 14, 2023 9:36 am Post subject: |
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No matter the CPU, if you run it at max load, all cores/threads running (if multi) with lots of computations, then you are likely to see TDP or even beyond it (marketing sucks), but for normal use, browsing, pdf viewing, etc the CPU won't use much power. And the cooling fan won't run much, so less noise.
I have a 3700x 65w, but under heavy load it can hit in the 100 watt range.
Doesn't matter whether AMD or INTEL, same thing.
For low power CPU, 3600x and 5600x are both 6 core, 12 thread, 65w processors and both come with heatsink, IIRC.
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szatox
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| Posted: Thu Sep 14, 2023 10:52 am Post subject: |
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| Quote: | | The primary concern was the full throttle noise levels. |
Do you feel like getting creative?
Bigger fans running at lower rpm are quieter than smaller fans pumping the same air.
Radial fans are much quieter than axial fans.
By stuffing the radiator in a vertical pipe you might be able to get enough convective cooling to not need a fan. Gotta calculate how big chimney you'd need to keep that beast of a CPU cool though. |
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pjp
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| Posted: Fri Sep 15, 2023 4:32 am Post subject: |
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| steve_v wrote: | | pjp wrote: | avoiding the larger coolers.
...
The primary concern was the full throttle noise levels. |
That's an inverse relationship most of the time. Larger coolers (and by extension larger diameter fans) provide more cooling at lower noise levels. |
Yes, but affixing coolers to was already questionable with the force required to complete the task. It wasn't much, but I also don't like flexing PCBs. The added weight is a concern, as well as the physical size requirements to house them (it would seem to preclude anything but large cases. I presume but don't know that they would fit in mid-towers. It isn't at all clear how to determine if a particular case would work, and that isn't taking into account airflow.
| steve_v wrote: | | As for passive cooling, it's certainly possible but given the large influence of airflow on heatsink efficiency it also tends to be an extremely expensive proposition for all but the lowest power CPUs. |
This is true. And not something commonly available. I wasn't able to find the post in recent years, but at one point, a user posted a link to some company that made passively cooled Intel based systems, loosely looking like car audio amplifiers (at least the amps of some decades past, I haven't seen any in a long time). The consumer market for them doesn't exist, so they're unfortunately an unrealistic option.
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pjp
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| Posted: Fri Sep 15, 2023 4:51 am Post subject: |
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| Syl20 wrote: | | So you want something more powerful, more energy-efficient, and cheap (how much, by the way ?). You actual CPU is 14 years old, and known to be quite powerful at that time, but not for its temperance, far from it. |
. The triad you mention is of course one of compromises. Regarding the 35W CPU, it had some specs that were surprisingly comparable to my Phenom. I would guess that the new Zen Athlon performs better than my Phenom, but by how much? To accommodate the new CPU requires at least new memory, motherboard, and PSU. So the ~$130 CPU becomes in the $350 range. For a questionable amount of improvement, that's not easy to justify. If I were looking for a secondary system, I'd give it more consideration.
As for power, I'll likely be going with low to mid Ryzen offerings. On the high end, the Ryzen 7 5800X Vermeer is tempting, but only if I can find it on sale when I'm ready to buy. On the low end (from when I was looking yesterday), the Ryzen 5 3600 Matisse is a strong contender (on sale, <$100). From what I can tell, that 5800X doesn't come with a cooler and is 105W, so I presume it would be best with the larger coolers. 65W models often come with coolers, and they don't seem as large, although some 65W models don't come with coolers.
| Syl20 wrote: | | Did you consider second-hand hardware ? |
In general, no. I was able to get a couple of old laptops that I plan to use for testing. Given that the system is about 10 years old, I don't want to extend it for too much longer.
| Syl20 wrote: | | Otherwise, perhaps you should have a look on Intel products, known to be less burning for the same performance. And the price should not be a problem, if the CPU is sufficiently old : Core I5 4570, or Core I7 4770, for example, are safe bets, for the tenth of the price of the Zen+ you mentioned. And if you want more, the next generations are not really more expensive... |
The total cost is a factor. At some point, the expense isn't worth the marginal gains. For about the same price as the i7 I can get the Ryzen 5 4500 Renoir. It has 24MB less L3 cache (and only PCI 3) than the Matisse that I mentioned. The Matisse seemed worth $15. Depending on when I buy and what's available around then.
| Syl20 wrote: | | Add a low-profile cooler if you don't have the room for a fridge, and you'll be the happiest user in the world. |
I'm leery of "high end" solutions. I believe it was a Noctua CPU cooler that I couldn't get a replacement fan for, so I replaced the entire thing with the stock cooling solution that came with the CPU. That was the first CPU fan that failed on me as the original owner. Unfortunately all of the CPU coolers I've seen appear to have custom parts that I guess aren't easily replaced, which reinforces my interest in avoiding the high end XXL / XX$ cooling solutions. The Wraith Spectre that comes with many Ryzen CPUs appeared to be available for $10. I did buy some Be Quiet case fans as replacements for some stock fans that died.
Overall I'm looking for performance gains that are "worth" the total cost of upgrading. That my current CPU might be in the 95W range along with die improvements will inherently come with efficiency gains. And if I go with a 65W processor, it's probably going to save there too. To round out my thinking, if I could get the 35W Zen Athlon for about $60, I might build 2 systems. Now that I've mentioned it, I think I'm going to see what it would cost.
Thanks for the comments! Having to think about it isn't a bad thing :)
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pjp
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| Posted: Fri Sep 15, 2023 5:07 am Post subject: |
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| Anon-E-moose wrote: | No matter the CPU, if you run it at max load, all cores/threads running (if multi) with lots of computations, then you are likely to see TDP or even beyond it (marketing sucks), but for normal use, browsing, pdf viewing, etc the CPU won't use much power. And the cooling fan won't run much, so less noise.
I have a 3700x 65w, but under heavy load it can hit in the 100 watt range.
Doesn't matter whether AMD or INTEL, same thing.
For low power CPU, 3600x and 5600x are both 6 core, 12 thread, 65w processors and both come with heatsink, IIRC. |
At some point in the now not applicable past, AMD had been in the "Good" quadrant for TDP marketing while Intel was not. I think that was pre-Zen, but I'm not certain.
Some 65W processors do come with coolers, but not all. I thought that wattage might have been an indicator on where the larger coolers were required, but that isn't certain. I recall past CPUs simply had some without coolers so enthusiasts could do their own thing. For no more than the added cost of the stock coolers, I'm now a convert on liking that at least as an emergency backup -- now going on two or more years of "backup" service :).
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pjp
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| Posted: Fri Sep 15, 2023 5:10 am Post subject: |
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| szatox wrote: | | Quote: | | The primary concern was the full throttle noise levels. |
Do you feel like getting creative?
Bigger fans running at lower rpm are quieter than smaller fans pumping the same air.
Radial fans are much quieter than axial fans.
By stuffing the radiator in a vertical pipe you might be able to get enough convective cooling to not need a fan. Gotta calculate how big chimney you'd need to keep that beast of a CPU cool though. |
Interesting that you mention radial fans. I can only guess that I was looking at computer cooling, but I had come across information indicating "squirrel cage" fans were a lot noisier. Perhaps that was only of certain applicable sizes. Or maybe it was wrong, or I misunderstood.
One of the reasons I chose my previously mentioned Noctua was for the larger fan. Not being able to replace the fan made that somewhat less useful. I do think the stock fan is likely louder, but not by a lot most of the time. It's also been long enough that I don't remember how quiet the old one was (before it died! :).
I've never managed to have much of a "shop" workspace, so the creativity would have to be limited to minimal mess and tools. I have at times considered trying to help exhaust heat away from the back of cases, but I don't have any means to verify that it would be helpful rather than detrimental.
Out of curiosity, do you have any reference terms / specs to search for "appropriate" radial fans?
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steve_v
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| Posted: Fri Sep 15, 2023 6:58 am Post subject: |
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| pjp wrote: | | The added weight is a concern, as well as the physical size requirements to house them (it would seem to preclude anything but large cases. I presume but don't know that they would fit in mid-towers. It isn't at all clear how to determine if a particular case would work. |
That's one of the reasons I went with the U12A. Being 120mm, it'll fit in pretty much any mid-tower ATX case (in my case this cheapo, with some minor mods to improve airflow). It'll also take any standard 120x25mm fan(s), and the ones included can be purchased separately if a replacement were needed.
For the lower TDP CPUs you're mentioning a 92mm cooler would probably do fine as well, and the same holds wrt fans for noctua's offerings in that category.
Cooler clearance (primarily height above the board) is indeed a concern these days, but most case manufacturers publish maximum cooler height in their specs.
On cooler support, I actually CNC cut a bracket to secure the top of my cooler to the case... But that's more because I wanted to play with cutting aluminium on my modified desktop router than because it was needed. Motherboard PCBs are surprisingly strong, and unless you're transporting the machine regularly it shouldn't be a problem.
| pjp wrote: | Interesting that you mention radial fans. I can only guess that I was looking at computer cooling, but I had come across information indicating "squirrel cage" fans were a lot noisier. Perhaps that was only of certain applicable sizes. Or maybe it was wrong, or I misunderstood.
|
If we're talking about the same thing (I've always used/heard the term "centrifugal fan" for designs where airflow is radial / perpendicular to the rotation axis), I agree. I haven't seen one used for a desktop CPU cooler since ~2010, and those were notoriously noisy.
These days the only place you tend to see them is where space is limited or high static pressure is needed such as laptops, ducted cooling solutions in servers, and "founders edition" or server market "blower style" GPUs which exhaust through the PCI slot bracket. Those are also notoriously noisy, though that likely has more to do with high static pressure and airflow velocity than the fan design itself.
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szatox
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| Posted: Fri Sep 15, 2023 12:30 pm Post subject: |
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| Quote: | | Those are also notoriously noisy, though that likely has more to do with high static pressure and airflow velocity than the fan design itself. |
The squirrel-cage actually almost looks like it was specifically designed to be noisy, with those very narrow blades running at high velocity.
I've been thinking about something more similar to a centrifugal fan, with fewer but wider blades which would translate to lower attack speed and less turbulent flow. The point is to get rid of the sharp "beat" from blades.
The downside is that it would need to be bigger in diameter, 'cus it's a least 2x blade width + intake, and we can't really make the intake much smaller.
Still, shouldn't be an issue inside a tower-type case.
| Quote: | | Out of curiosity, do you have any reference terms / specs to search for "appropriate" radial fans? |
Unfortunately, those are not very popular, so it's difficult to find anything. I'll give it a closer look once I need it.
Searching for DC brushless blower gave _some_ results though
The 2 parameters to compare will be noise and airflow (must meet cpu's and radiator's demand).
BTW, a funny thing I found recently: a "silent" drone propeller with 2 blades at a relatively small angle and a counterweight. It was built this way to spread the energy wasted as noise over multiple frequencies instead of emitting one sharp tone like evenly spaced blades do, so it would drown in the ambient noise easier. |
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pjp
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| Posted: Fri Sep 15, 2023 4:07 pm Post subject: |
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| steve_v wrote: | That's one of the reasons I went with the U12A. Being 120mm, it'll fit in pretty much any mid-tower ATX case (in my case this cheapo, with some minor mods to improve airflow). It'll also take any standard 120x25mm fan(s), and the ones included can be purchased separately if a replacement were needed.
For the lower TDP CPUs you're mentioning a 92mm cooler would probably do fine as well, and the same holds wrt fans for noctua's offerings in that category.
Cooler clearance (primarily height above the board) is indeed a concern these days, but most case manufacturers publish maximum cooler height in their specs. |
The cost isn't inherently the problem, it was availability of replacement fans. Since that's possible, I'll consider that aspect mostly solved. Physical size may still be a factor. Although options for cases sitting on a desk are mostly gone or mini-ITX or proprietary. I haven't decided what to do about a case. I may use the larger, Fractal Design case that is my current system as a file server and go with the older, slightly smaller case for the upgrade. Having only one system has it's appeal, but has the downside of being offline until the upgrade is finished. In the interests of keeping costs down, I'm not likely to buy a new one.
| steve_v wrote: | | On cooler support, I actually CNC cut a bracket to secure the top of my cooler to the case... But that's more because I wanted to play with cutting aluminium on my modified desktop router than because it was needed. Motherboard PCBs are surprisingly strong, and unless you're transporting the machine regularly it shouldn't be a problem. |
Famous last words :) Keep in mind that my current systems is ~10 years old, and if gains are to be incremental, software has to yield to hardware limitations.
| steve_v wrote: | If we're talking about the same thing (I've always used/heard the term "centrifugal fan" for designs where airflow is radial / perpendicular to the rotation axis), I agree. I haven't seen one used for a desktop CPU cooler since ~2010, and those were notoriously noisy.
These days the only place you tend to see them is where space is limited or high static pressure is needed such as laptops, ducted cooling solutions in servers, and "founders edition" or server market "blower style" GPUs which exhaust through the PCI slot bracket. Those are also notoriously noisy, though that likely has more to do with high static pressure and airflow velocity than the fan design itself. |
Sounds similar. The closest I can find is this 8" "cross flow" fan, although the picture isn't great. This one for a fireplace is a bit clearer, but much larger than what I had seen previously.
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pjp
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| Posted: Fri Sep 15, 2023 4:57 pm Post subject: |
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| szatox wrote: | The squirrel-cage actually almost looks like it was specifically designed to be noisy, with those very narrow blades running at high velocity.
I've been thinking about something more similar to a centrifugal fan, with fewer but wider blades which would translate to lower attack speed and less turbulent flow. The point is to get rid of the sharp "beat" from blades.
The downside is that it would need to be bigger in diameter, 'cus it's a least 2x blade width + intake, and we can't really make the intake much smaller.
Still, shouldn't be an issue inside a tower-type case. |
Hah! I presume they were primarily designed to fit in a limited space. These do make the chimney solution you suggested more understandable than the versions I had in mind.
| szatox wrote: | Unfortunately, those are not very popular, so it's difficult to find anything. I'll give it a closer look once I need it.
Searching for DC brushless blower gave _some_ results though
The 2 parameters to compare will be noise and airflow (must meet cpu's and radiator's demand). |
It very much seems as much a hobby looking for a solution as a problem for which it is the obvious solution :)
I wonder how well it might work with a coiled chimney rising around the outside of a case. When I had considered trying to build a custom case, I was most drawn to cylinders and cubes.
| szatox wrote: | | BTW, a funny thing I found recently: a "silent" drone propeller with 2 blades at a relatively small angle and a counterweight. It was built this way to spread the energy wasted as noise over multiple frequencies instead of emitting one sharp tone like evenly spaced blades do, so it would drown in the ambient noise easier. |
Given all of the functional needs for fans and blades, I find it interesting that it took drones to seemingly make some significant changes. I"m guessing weight was the major motivator. I've never been interested in drones other than what they're capable of, and the occasional tech article about some new development, such as a blade style.
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steve_v
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| Posted: Fri Sep 15, 2023 5:09 pm Post subject: |
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| pjp wrote: | | The closest I can find is this 8" "cross flow" fan, although the picture isn't great. This one for a fireplace is a bit clearer, but much larger than what I had seen previously. |
Those are the kind of things I'd expect to see in a fan heater or maybe an aircon duct, not so much a PC. I really don't see why one would even consider such a thing except to work around physical mounting limitations (i.e. a wide but very flat "pizza-box" case design).
When somebody says radial/centrifugal/blower CPU cooler, what I think of is the likes of this stupidity. I actually had one of those back in the pentium 4 era, and I can attest that the noise they make is pretty appalling. The "don't stick finger in here" decal is also not a joke. 
I replaced the centrifugal blower with an axial fan in short order, for considerably less noise and no drop in cooling performance, which is why I can only find the heatsink itself in my junk box today.
Had the centrifugal fan been paired with a higher fin-density heatsink to take advantage of improved static pressure it might have been worth it, but as it was an axial fan did just as well, with less obnoxious whine.
These days centrifugal CPU coolers are usually only found in proprietary [U]SFF cases and laptops, where the fan is much shorter axially and mounted axis-vertical to draw air up through the heatsink and exhaust directly out the back of the case. I've got a couple such machines here, and the only reason they use this design is that the case is a mere 70mm high.
You might also remember this common use for centrifugal fans, I've still got one in service cooling the voodoo card in my retro-gaming super-7 (K6-2) box.
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pjp
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| Posted: Fri Sep 15, 2023 10:46 pm Post subject: |
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I was probably looking at small enclosures or similar. I'm guessing I read about someone trying it or wanting to, but I don't recall. Conceptually, the Aero4 doesn't seem like a bad idea, but I also presume that if it was better, it would be used, even if it was primarily a more expensive option. I vaguely remember the other one, but mostly the kind for laptops.
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szatox
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| Posted: Fri Sep 15, 2023 11:08 pm Post subject: |
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| Quote: | | Hah! I presume they were primarily designed to fit in a limited space |
Yes, absolutely.
It's just impossible to put an axial fan in a 1cm thick case. At this scale, a piston pump would probably move air faster than that.
Piezoelectric fans seem to be still in development phase.
| Quote: | | These do make the chimney solution you suggested more understandable than the versions I had in mind |
"These" certainly make much more sense than puny cages. They are actually used in industrial applications due to their resilience; e.g. don't get damaged by sawdust from machining stuff in workshops.
And, apparently, they're also used to run air through office vents, because they're quieter and more stable than axial fans.
The chimney I mentioned was with passive cooling in mind though.
Put the CPU at the base of a pipe, it heats the air, the air expands and raises through the pipe. The longer pipe you have, the more draft this warm air will cause.
20 years ago Apple had a line of desktops cooled this way. You might remember those translucent TV boxes with CD trays at the bottom, whatever they were called. AFAIK they were cooling CPUs with heat from CRT monitors placed right above.
If you put your hand above the exhaust, the draft was strong enough you wouldn't know there was no fan inside, yet the only spinning thing you could hear was the hard drive.
| Quote: | | Given all of the functional needs for fans and blades, I find it interesting that it took drones to seemingly make some significant changes. I"m guessing weight was the major motivator. |
I doubt you can make a propeller with counterweight lighter than a propeller without dead weight. Making it asymmetrical comes at a cost.
However, children toy drones which weight next to nothing notify me of their presence from like half a kilometer away (like in: I did not expect them to be there). And even those things can carry cameras. A quieter drone will annoy fewer neighbors.
| Quote: | | When somebody says radial/centrifugal/blower CPU cooler, what I think of is the likes of this stupidity. I actually had one of those back in the pentium 4 era, and I can attest that the noise they make is pretty appalling. The "don't stick finger in here" decal is also not a joke. |
Well.. It certainly was a stupidity. Who made those blades run in the open?  |
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pjp
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| Posted: Fri Sep 15, 2023 11:42 pm Post subject: |
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Oh, that kind of chimney. Seems difficult to test. I presume the basic engineering concepts could provide a starting point.
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