Hardware Selection for AMD64 + Linux?

MrClever asks: "After a disaster involving my cat, a pot of coffee and my workstation, I am now in the market for a new machine. I thought I'd jump on the AMD64 wagon and keep running Linux. After some initial investigation, it became clear that ATi, Promise and other manufacturers don't have 64bit drivers for Linux, which rules out most motherboards with onboard P/SATA RAID, thus limiting my available choices. I know you can run 32bit on AMD64, but if I wanted that I'd get an AthlonXP. So, what AMD64 hardware is the best supported in 64bit mode under Linux? Seems NVidia have 64bit drivers, does anyone else?"

Comments

Software selection

[hackstraw]

Maybe you should either tell us what kind of applications that you want to run. Video drivers aren't too important for a headless box that sits in a closet.

I'm guessing that you are planning on running very large memory applications (> 2 Gig per process), otherwise 64bit support is useless. Especially since _many_ of Linux's applications still have 32bit limitations, even when compiled for 64bit platforms. I've run 64bit linux for 6 or 7 years now, and I'm still pissed that I run into 2Gb file size limits. Remember an int on 64bit linux is still 4 bytes as it is on 32bit systems, so each application has to either use size_t or long to get 64bit integers (which will work on either a 32bit or 64bit machine). Just today I had a user mail me with an error with rcp because it could not transfer a file that was 2.1Gigs. I believe 'cat' has the same limitation, unless it is done as a pipe. For example, cat over_2Gig_file > /dev/null will fail, but cat /dev/null will not. You will find these limitations from time to time, and rarely does the platform matter.

Also, Linux has other limitations like it cannot access a block device over 1 or 2 Tb (depending on the kernel version).

I think that the 64bit hype is amusing. I'm not sure, but an amd64 system running int 64bit mode might be slower than a 32bit offering from either intel or amd. You will have to look at the numbers, but they are hard to find. All of the benchmarks for the opteron that I have seen were run on 32bit applications that were complied with the _Intel_ compiler, or sometimes gcc (and then I believe that they were in 32bit mode).

My recommendation is to 1) kill you cat (just kidding), and 2) just by a stock machine that is either 32bits or look for an integrated 64bit system for linux already, or get a really nice 64bit system (but I wouldn't put Linux on one of those).

Re:Software selection

[Paladine97]

Having twice the general purpose registers will typically improve performance 10-20% just by recompiling everything into 64 bit mode. The grandparent is smoking some major crack.

Re:Software selection

[hackstraw]

Having twice the general purpose registers will typically improve performance 10-20% just by recompiling everything into 64 bit mode.

Data please? this thread mentions povray, well this povray benchmark site clearly shows that the $259 amd64 chip is slower than the $200 Intel offering.

this site has some benchmarks. Note that they use gcc for the pentium machines, which is not a very good optimizing compiler. For floating point apps, I typically see 2x speedup when using the Intel compiler (like oggenc, povray, etc). I cannot say which is faster, but being that there is no good (free) compiler for the amd64 you will just have to take the numbers for what they are (meaningless).

The grandparent is smoking some major crack.

Damn, I've gotta be more discreet.

Re:Software selection

[alienw]

Ummm... Lay down the crack, man. The AMD64 platform offers many more advantages than just it's 64-bitness.

First, the Opteron has an integrated memory controller. That means FAST memory access. If you are running two of them on a dual-channel board, you get a really fast NUMA configuration. That's very important for applications that actually need to calculate stuff, assuming your OS supports it.

Second, it has twice the number of registers. That gives you a large performance advantage over IA-32 because apps don't need to constantly swap out variables into RAM.

Third, the Opteron has 1 meg of L2 cache. That is twice than what Athlon 64 or Mac G5 has, for about the same price. It sure as hell makes a difference, even for normal desktop use.

Also, I see no reason whatsoever to buy an expensive pre-built system when a really nice machine can be put together in a few hours for well under $900. I just upgraded my workstation to an Opteron 140 for only about $600. That's with a server-class board, 400W power supply, and 512 megs of DDR400 registered ECC RAM. Apple doesn't even offer the same features, and a comparable machine costs about $2000 from them. Not to mention that OS X is 32-bit.

Re:don't buy an Athlon 64 until new socket comes o

[Anonymous Coward]

because a lot of software can use 64 bits of data at a time in their maths loops which makes everything a lot faster ?

This proprietary driver situation sucks

[7-Vodka]

For some reason I'm finding myself extremely upset at companies refusing to release the specs to their harware and forcing linux users to use proprietary drivers. That's not what linux is about. There are a lot of us who actually care about using free software.
What's more it's really fucking inconvenient and I hate being forced to use lower-quality software because of greed.

I'm sure there are more than a few upset nforce users for example. The ones who aren't upset, wait till they find a bug or find their performance isn't up to par and take their problems to the lkml. They'll find out that since their platform is a black box they can't get any support and are stuck with what they're forced to use.

I was going to buy an nforce3 dual opteron motherboard but I can't stomach having to use a bunch of proprietary drivers.

I also used to think that it was ok if just the video card had a proprietary driver. It's just one driver afterall right? well apparently the slippery slope has slipped. From now on I will refuse to use any drivers which taint the kernel.

On top of all this, I have to really question the legality of all these proprietary drivers that are popping up. I know there were some threads on the lkml about this recently.
Basically they came to the conclusion that if a driver was written for another OS and merely released for linux as an afterthought it was legal. However if it was written for linux it came under a derrivative work and was not legal.

Either way... PROPRIETARY DRIVERS SUCK