How will 32-bit apps run under 64-bit OSes like XP with AMD-64?

donny_paycheck · Aug 9, 2004

As some of you may know I'm setting up a game server with a pair of Opterons and I'd like to use NUMA. Problem is, only 64 bit OSes are NUMA-aware. Except that I've read that XP-64 uses an emulation layer to run 32 bit apps, which hampers performance measurably.

Anybody have any dirt on this? If there's a performance reduction via the emulation layer I'll just go with a 32-bit OS for the time being, since the games I'll be hosting are categorically 32-bit applications. If it's a minimal or nonexistent degradation, I'll bite it and install XP-64 when it's out at the end of the month.

schnikies79 · Aug 9, 2004

No, the opteron does not use emulation for 32bit. It is a 32bit processor with 64bit extentions added to it, so there is no drop in 32bit processing peformance. Actually it's one of the fastest processors for 32bit. The Intel Itanium is the only 64bit processor that i'm aware of that uses emulation for 32bit.

-d

JigPu · Aug 9, 2004

32-bit software runs pretty much just as fast (and I believe I've seen a few cases where it's faster) on Win64 as Win32. 32-bit programs aren't emulated, but instead "translated". The underlying instruction set is exactly the same minus a few additions, so the only thing that need to be done really is translating all 32-bit function calls into 64-bit calls instead.

This article gives a quick overview of WOW64 (how Windows64 gets 32-bit programs running). Also, an blog with some interesting links.

JigPu

donny_paycheck · Aug 10, 2004

Thanks for the replies. I knew the Opterons had 32-bit capability, but I was wondering if a 64-bit OS would cause the slowdown by running an emulator, rather than letting the 32-bit part of the K8 do its own thing:

JigPu said:
so the only thing that need to be done really is translating all 32-bit function calls into 64-bit calls instead.

...like this, I thought, might incur a performance penalty.

But I'm set now. No more worries, I'll go with a 64-bit OS.

dreIU · Aug 10, 2004

donny_paycheck said:
I'll bite it and install XP-64 when it's out at the end of the month.

Windows XP-64 comes out at the end of August? As in the final version??

donny_paycheck · Aug 10, 2004

dreIU said:
Windows XP-64 comes out at the end of August? As in the final version??

I was checking Microsoft's site a few days ago and they had the ship date as August 31st.

Edit: I was wrong. Not until 2005:

It looks as if early adopters of the Athlon 64 will have to wait a bit longer for a 64-bit Windows OS to run on their systems. Microsoft has pushed back the release of the first version of Windows XP 64-bit Edition for 64-bit Extended Systems (XP64E64ES?) until the first part of 2005. Windows Server 2003 SP1 and the initial 64-bit version of Windows Server 2003 will also be delayed until next year.

http://arstechnica.com/news/posts/20040728-4046.html

dreIU · Aug 10, 2004

Ah well... that's OK I suppose, as long as I can get it for 5 bucks as part of my student discount :clap:

donny_paycheck · Aug 10, 2004

Incidentally, what's another good 64-bit OS? Is Windows Server 2003 with AMD-64 support out yet?

I'd really like to get a 64-bit OS installed on this thing but since XP-64 is out of the question for the moment, does anybody know of a possible substitute?

alien dork · Aug 11, 2004

fedora 64bit is out

. you can try that! i installed the win64 beta version on my computer and it is very fast, as far as i can tell it is faster than regular xp. there is a downside to this. some of the xp(32bit) programs do not work on win64(actually a lot of them don't).

Gnufsh · Aug 11, 2004

There are many linux distros for x86-64. You could try dual-booting one of those with 32-bit windows. As far as windows versions that support x86-64, I don't really know.

How will 32-bit apps run under 64-bit OSes like XP with AMD-64?

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