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cons of a 64bit installation on laptop, and hardware support
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broli
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PostPosted: Fri Apr 12, 2013 6:27 pm    Post subject: cons of a 64bit installation on laptop, and hardware support Reply with quote

HI!, i have been using gentoo for years, but this is the first time i post. sorry for the broken English, as its no my main language

when i was deciding on the post title, i couldn't find a good way to describe what i want. i hope the one i chose does not scare people away :P

i bought a new laptop from dell. it has a Intel core i7 processor, 8gb of ram, an SSD and a HDD, and a muxless "double" video card thingy that uses an intel chip and a ATI chip.
While i wait for it to arrive by mail, i started googling about different aspects of the hardware, guides to optimize or get to work some hardware, ect.

I have always used the 32bit gentoo, and tough this might be a good opportunity to switch to a 64 one.
First i tried searching the forums or internet but didn't quite found what i want, with many of the post also being 2 years old or more, so i decided to ask here.

I have 2 questions/issues.

1) late or no access to "latest" binary packages:
Main example is the catalyst drivers for the ATI half of the dual video. I have searched and found its possible to benefit from the low power/high power capabilities, but for that, you kinda need a specific combination of versions from both packages (catalyst and intel drivers).
My fear is that the 64 platform might have less "priority" in some regards, and will make my life very difficult, because i wont have access to the full range of stable and unstable releases from ATI
I hope this is just my imagination and not a real problem.
This was an example, i cant think of another good one but im sure there are others.

2) multilibs for 32 bin apps
this one is much simpler. will i be able to install 32bit library ?
for example, i play Wakfu. the game requires some libraries, even some old ones. in my current 32bit gentoo i had to install 2 versions of some libraries because the game required an older version.
how hard, if at all possible, would be to get this working in a multilib system?

i have read that 64bit systems can run 32bit apps with no problems if all package dependencies are met. i wonder how that translates to real day to day usage.
the only binary packages i use are Wakfu (game), maybe virtual box (cant remember if i use the binary or not), and maybe some firmware (the wifi chipset looks like its supported by the kernel, but needs external Firmware)

so, to sum all up, i think the real question here is how is the state of 64 bit integration now a days?
so far, looks like i will stick to a 32bit, as the profit does not out-weight the trouble..

thanks in advance


Last edited by broli on Fri Apr 12, 2013 9:08 pm; edited 1 time in total
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NeddySeagoon
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PostPosted: Fri Apr 12, 2013 6:50 pm    Post subject: Reply with quote

broli,

Welcome to Gentoo.

Your English is plenty good enough and its my only language :(

64 bit development leads 32 bit development now and has done for some time.
The break even point between a 32 bit install and a 64 bit install is about 2G of RAM.
With less than 2G RAM, there is not a lot to choose. With more than 2G, a 64 bit install is better.
A 32 bit install on an i7 is like keeping a Ferrari just to drive to the corner shop :)

You can choose a multilib install and build your kernel to support 32 bit code, so you can run both.
I cannot provide specifics as I use no-multilib.

Virtualbox is a 32 bit application. On multilib, you can build it from source. I must use Virtualbox-bin.

Get your install working with the Intel video driver. Muxless means you have 1 1/2 video cards. Only the Intel graphics card can refresh the display, so if you switch to the ATI graphics, you get a black screen. The two cards have to cooperate when the ATI card is in use.

Firmware will not matter, it just passes through your system as data, on its what to wherever its needed.
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broli
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PostPosted: Fri Apr 12, 2013 7:09 pm    Post subject: Reply with quote

NeddySeagoon wrote:

64 bit development leads 32 bit development now and has done for some time.
The break even point between a 32 bit install and a 64 bit install is about 2G of RAM.
With less than 2G RAM, there is not a lot to choose. With more than 2G, a 64 bit install is better.
A 32 bit install on an i7 is like keeping a Ferrari just to drive to the corner shop :)

I like the analogy :P
so you think there will be "better performance" with the 64 bit install?
i dont usually do intensive tasks, except for the fun "look i am running 3 virtual linuxes!!" XD
the most cpu intensive app i use is emerge, and some game here and there.
NeddySeagoon wrote:

You can choose a multilib install and build your kernel to support 32 bit code, so you can run both.
I cannot provide specifics as I use no-multilib.

I just wanted confirmation. ill do the research myself.

NeddySeagoon wrote:

Get your install working with the Intel video driver. Muxless means you have 1 1/2 video cards. Only the Intel graphics card can refresh the display, so if you switch to the ATI graphics, you get a black screen. The two cards have to cooperate when the ATI card is in use.

i found how to make use of both.
with the proprietary drivers kinda works by it self after changing a few lines in your xorg.conf.
its pretty simple once you read it. the first impression is "how could i not think of that, is so obvius"

its also posible with the open source drivers,using software to doit. its kinda like an off screen buffer where the 2 chips merge they screens before sending it
more info ehre if you are interested
https://forums.gentoo.org/viewtopic-t-909802.html
NeddySeagoon wrote:

Firmware will not matter, it just passes through your system as data, on its what to wherever its needed.

thats good to know

thanks for your reply
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krinn
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PostPosted: Fri Apr 12, 2013 8:57 pm    Post subject: Reply with quote

NeddySeagoon wrote:

With less than 2G RAM, there is not a lot to choose. With more than 2G, a 64 bit install is better.
A 32 bit install on an i7 is like keeping a Ferrari just to drive to the corner shop :)


I like driving to the corner shop, but i don't think the analogy fit well.

- 32bits support without doing anything 4G of ram
- 32bits could handle more than 4g as well
- but 32bits will always be able to only allocate 4G at max
- 32bits on the other end is plenty times faster to access and read memory

So to me, if you have more than 4G the 32bits should be drop as someone with more than 4G will certainly have that much to handle huge applications, that could wish to allocated and use 4G. In that case 64bits is better. And without even the allocation, this time accessing more than 4G will be done with PAE that will decrease the access times badly, removing fast memory access 32bits provide.
But if you are tied to 4G, the 32bits will be faster, because of access times to that memory.

Only scientific applications and big multimedia programs will get limited, it's easy, it's the same kind of program that love to eat G of ram like cake. Certainly not the kind of program a laptop was made to run.

Something you could test and see with a livecd, run it 64bits hdparm -T /dev/somediskblock
Now redo under 32bits livecd

So i disagree with neddy there :)
32bits with 4G is faster than 64bits for sure, just because accessing memory is what your OS is doing all the time.
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broli
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PostPosted: Fri Apr 12, 2013 9:07 pm    Post subject: Reply with quote

Wile I was reading your post, I was confused about the 4g you talked about.

And then I realized, I made a mistake. :-P

The laptop will have 8gb of ram. Sorry for the mistake. I'll edit the op
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PostPosted: Fri Apr 12, 2013 9:09 pm    Post subject: Reply with quote

krinn wrote:
Only scientific applications and big multimedia programs will get limited, it's easy, it's the same kind of program that love to eat G of ram like cake. Certainly not the kind of program a laptop was made to run.
I used to believe exactly this. Tongue firmly in cheek, I would say, "I love 64 bits! The more unused precision on the left of my integers, the better!" However, I've been told that this isn't the whole story. In 64-bit mode, the CPU has more general purpose registers, sometimes resulting in better, faster-running code. That said, I don't have a good feel for it. Memory bandwidth is going to be higher, for sure. Whether that's offset by better code more often than not, I don't know.

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PostPosted: Fri Apr 12, 2013 9:16 pm    Post subject: Reply with quote

krinn,

I think that you over simplify things.
A 32 bit install uses 32 bit pointers and can address at most 4G of both Physical and Virtual memory. In practice, because of memory mapped IO, the most physical RAM that can be addressed can be as low as 3.2G.

To go beyond 1G Physical RAM on a 32 bit system, you need the first if the Himem tricks. This costs memory access time. As you go past 4G, PAE makes matters worse.

On a 64 bit install, these memory problems vanish. You have 64 bit pointers and the virtual address space that goes with them.
True - 64 bit pointers take up more memory, so 64 bit code tends to be bigger than 32 bit code. The memory lost to memory mapped IO, just before 4G can usually be mapped to above 4G, instead of vanishing. There is a 'memory hole' in the physical RAM address space.

Also, in 64 bit mode you get more CPU registers - this is a good thing on x86, which is a register poor arch.

In practice, most memory accesses will be CPU cache hits, so there is no speed difference between 32 and 64 bit modes.
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krinn
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PostPosted: Fri Apr 12, 2013 9:36 pm    Post subject: Reply with quote

With 8g i think i already told broli what arch i would pick.

But just like the new registers would help, it's hard to say if it's enough to balance the size of param that are now double for each op.
Only real benchmark would tell, and i think benchmark would gave 32bits for that program and 64bits better with this one.
But for general purpose usage, i still think the 32bits memory speed kick 64bits ass bad.

Just like 64bits vs 32bits when it comes to precision, well, in 32bits mmx, sse... exists and sse allow 128bits precision, so for a program not handling them, 64bits will win, but if you handle them, it would be interesting to see the result no ?

So without real proof, if someone could say 64bits is faster, i could too says 32bits is faster then no?
And i don't think i have over simply it much more than anyone here :)
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PostPosted: Fri Apr 12, 2013 9:48 pm    Post subject: Reply with quote

Krinn,

If you feel adventurous, try the new 64 bit memory model ... its all the 64 bit instructions but it uses 32 bit pointers.
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krinn
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PostPosted: Fri Apr 12, 2013 9:55 pm    Post subject: Reply with quote

I was thinking about that in fact NeddySeagoon, as i seen that now the toolchain handle x32 without hack.
And even i didn't dig it far, i've seen gentoo has done another awesome job at it ! As gentoo already provide a stage file full x32 ready. Without saying it's the only distro (as i said i didn't read too much), it's clearly one of the few that is x32 ready.

Edit: add link to x32, to show gentoo rocks (look at Current Status)
https://sites.google.com/site/x32abi/
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PostPosted: Fri Apr 12, 2013 10:28 pm    Post subject: Reply with quote

memory access on 64bit is slower?
will this have an impact in my decision to use tmpfs on /tmp and others?
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PostPosted: Fri Apr 12, 2013 10:37 pm    Post subject: Reply with quote

broli wrote:
memory access on 64bit is slower?
will this have an impact in my decision to use tmpfs on /tmp and others?


As of today, the slowest memory you could get will still always be amazing faster than an harddisk, so no.
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PostPosted: Fri Apr 12, 2013 10:41 pm    Post subject: Reply with quote

Memory access isn't slower. Objects (instructions, integers, pointers) are bigger. Thus, the memory bandwidth used will be greater. Neddy's right that, for cache hits, there's no difference; for cache misses, there's is. How much of a difference is very application-specific.

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PostPosted: Fri Apr 12, 2013 10:55 pm    Post subject: Reply with quote

Processor's implementation on consumer grade laptops is : Poor !
The higher the grade of the cpu, the poorer the design !
Wait states everywhere !
Forget the cpu !
Forget the amount of ram !
Silly question : What's the access time of that ram ?

With systems like this, the more powerful the cpu is the faster you... wait !

You wont' always wait !
You won't wait when the cpus can find what they need in their caches.

=> Don't waste the caches !

Consumer grade 64 bits applications waste the cache !
Consumer grade 32 bits applications waste it... less !

With 64 bits consumer grade applications running on consumer grade laptops, you actually wait... faster !
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PostPosted: Sat Apr 13, 2013 12:17 am    Post subject: Reply with quote

Ever since I switched to 64-bit, I haven't looked back. It might be true that there were some issues when 64-bit was rolling out (e.g. hibernation never worked reliably, at least for me), but those are the things of the past. The only time I use 32-bit is when the machine itself is 32-bit. There might be a performance difference depending on what I'm running, but I don't think I'd be able to tell the difference.
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PostPosted: Sat Apr 13, 2013 12:23 am    Post subject: Reply with quote

solamour wrote:
The only time I use 32-bit is when the machine itself is 32-bit.

That's what I am doing.
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PostPosted: Mon Apr 15, 2013 3:35 pm    Post subject: Reply with quote

OK then.

ill try out the amd64 version and see how it goes.

thanks for all the replies
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