Prescott impact to prime95. - Page 3

ColdFury · 2003-07-10, 20:27

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Isn't there a 64bit WinXP floating around?

I believe there's a version of Windows 2003 for IA-64 available from Microsoft. It's one of those things you that are available "on request only" I believe.

Quote:

But I think the AMD64 platform, is more like a 48bit addressing processor.

Pretty much all processors are like that. Being able to address the full 64-bit memory space would create page tables that are much too unwieldy. Besides, no application is going to coinceivably need that much memory space. It's not a problem because the processor should be able to extend the virtual space in later processors transparently.

wfzelle · 2003-07-10, 21:02

Quote:

Originally Posted by nucleon

But I think the AMD64 platform, is more like a 48bit addressing processor. :)

True, but it's no big deal since you can't realistically use more than 282 terabytes anyway (for the time being). With a doubling of memory every 18 months, we should last for another 24 years. I'd rather not pay more for extra pins and increased core sizes that won't be needed until 2028.

BTW, here you can find an article about x86-64 and 64-bit computing in general: http://arstechnica.com/cpu/03q1/x86-64/x86-64-1.html

wfzelle · 2003-07-10, 21:16

Quote:

Originally Posted by nomadicus

I find it quite interesting that he notes the difference between servers/high-end workstations and the desktop. Servers needs to efficiently address beyond 32 bits. Does the desktop need that?

I don't think that 1GB is that much anymore. Some prosumers are already pushing the 64-bit boundary (video editing, photoshopping, etc). It's better to move to 64-bit now and have a gentle transition (instead of seeing all kinds of hacks to 32-bit apps).

Besides, the biggest advantage of x86-64 is not that it is 64-bit. The ability to fix some of the flaws of the x86 ISA (ie. few available registers) has a big effect on performance.

ebx · 2003-07-11, 04:53

Quote:

Originally Posted by wfzelle

Besides, the biggest advantage of x86-64 is not that it is 64-bit. The ability to fix some of the flaws of the x86 ISA (ie. few available registers) has a big effect on performance.

Why would it need a 64 bit processor to fix the shortage of registers?

wfzelle · 2003-07-11, 13:43

Quote:

Originally Posted by ebx

Quote:

Originally Posted by wfzelle

Besides, the biggest advantage of x86-64 is not that it is 64-bit. The ability to fix some of the flaws of the x86 ISA (ie. few available registers) has a big effect on performance.

Why would it need a 64 bit processor to fix the shortage of registers?

Because you need to convince developers to recompile their applications (possibly having to clean up their code) and ship multiple binaries. A fairly small player like AMD needs both the 64-bit fans* and the performance freaks to make x86-64 a success. The bigger the improvement, the greater is the chance that it will be adopted. It's telling that we've had to deal with very few registers for this long. It's clear that it is very difficult to achieve ISA improvements.

*Mostly server, workstation and (beowulf) cluster folk.

ebx · 2003-07-11, 16:24

So it is not really a x86-64 advantage. AMD is merely using this chance to add more registers.

Yea IA32 is hard to improve. That is why intel defines an all new IA64 architecture.

ColdFury · 2003-07-11, 21:13

I really wish AMD moved to a 3 operand format with x86-64, but I guess that would have required too much redesign of the decoders.

S3SJK · 2003-07-12, 09:02

Out of interest what performance advantages would that give?

nomadicus · 2003-07-12, 15:19

Three operands would combine two instructions into one.
Think of doing c=a+b
A two operand format would have to temporarily put the result (a+b) in a register, then execute another instruction to store it into c. A three operand format would perform the addition (a+b) and place the result straight into c.
I've over simplified the example being as different chip architectures (I was thinking of the VAX chip with its three operand format) will do it differently, but I hope you get the idea.
A three operand format is more complex than two which can a good thing or a bad thing depending on the chip's architecure goals.

ebx · 2003-07-13, 00:00

Quote:

Originally Posted by ColdFury

I really wish AMD moved to a 3 operand format with x86-64, but I guess that would have required too much redesign of the decoders.

If they did, it would not have been x86 any more.

ewmayer · 2003-07-14, 21:12

Quote:

Originally Posted by nomadicus

Quote:

Originally Posted by TauCeti

Looking at SPECfp2000 and SPECint2000 the 6 MB L3 Itanium-2 performs actually better compared to a power4 in 'fp' and only slightly worse in 'int'.

Example:

SGI Altix 3000 Itanium-2 1.5GHz 6MB L3 Specfp2000:2055 SPECint2000:1077

Intel says that they will achieve parity speeds with the Alpha chip in 2006 (give or take a year), but the latest ev7 1.1GHz Alpha chip (www.specbench.org) is rated
Specfp2000:1482
Specint2000:877

What's the deal? I take it that the SGI numbers correct? So I am wondering if I got bad info. or am I misinterpreting these numbers ?
john

Perhaps Intel is referring to parity in a per-clock-cycle sense.

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2003-07-11, 16:24	#28
ebx Aug 2002 101 Posts	So it is not really a x86-64 advantage. AMD is merely using this chance to add more registers. Yea IA32 is hard to improve. That is why intel defines an all new IA64 architecture.

2003-07-11, 21:13	#29
ColdFury Aug 2002 500₈ Posts	I really wish AMD moved to a 3 operand format with x86-64, but I guess that would have required too much redesign of the decoders.

2003-07-12, 09:02	#30
S3SJK Dec 2002 3×5 Posts	Out of interest what performance advantages would that give?

2003-07-12, 15:19	#31
nomadicus Jan 2003 North Carolina 366₈ Posts	Three operands would combine two instructions into one. Think of doing c=a+b A two operand format would have to temporarily put the result (a+b) in a register, then execute another instruction to store it into c. A three operand format would perform the addition (a+b) and place the result straight into c. I've over simplified the example being as different chip architectures (I was thinking of the VAX chip with its three operand format) will do it differently, but I hope you get the idea. A three operand format is more complex than two which can a good thing or a bad thing depending on the chip's architecure goals.