cons of a 64bit installation on laptop, and hardware support

[broli]

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

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

[NeddySeagoon]

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.
_________________
Regards,

NeddySeagoon

Computer users fall into two groups:-
those that do backups
those that have never had a hard drive fail.

[broli]

[krinn]

[broli]

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

And then I realized, I made a mistake.

The laptop will have 8gb of ram. Sorry for the mistake. I'll edit the op

[John R. Graham]

[NeddySeagoon]

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.
_________________
Regards,

NeddySeagoon

Computer users fall into two groups:-
those that do backups
those that have never had a hard drive fail.

[krinn]

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

[NeddySeagoon]

Krinn,

If you feel adventurous, try the new 64 bit memory model ... its all the 64 bit instructions but it uses 32 bit pointers.
_________________
Regards,

NeddySeagoon

Computer users fall into two groups:-
those that do backups
those that have never had a hard drive fail.

[krinn]

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/

[broli]

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

[krinn]

[John R. Graham]

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.

- John
_________________
I can confirm that I have received between 0 and 499 National Security Letters.

[aCOSwt]

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 !
_________________

[solamour]

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.
__
sol

[Jaglover]

[broli]

OK then.

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

thanks for all the replies