IA64 vs. Other 64-bit CPUs?

moZer asks: "There are countless reviews and comparisons between Intel's P4 and AMD's Athlon, but so far I haven't seen any benchmarks of IA64 versus other 64-bit CPUs. Is there anyone out there who has experience from working with the IA64 that can say something about its strengths and weaknesses?"

Comments

McKinley

[Oily Tuna]

The Itanium may never be really properly released as a production processor. McKinley is the one to watch for

UltraSPARC I

[spinlocked]

UltraSPARC I was Sun first 64 CPU, back in 95 as I recall. Of course you needed to wait until Solaris 7 before you got a 64 OS and hence the ability to use a 64bit address space. USI chips are detected by most 64bit versions of Solaris and it reverts to 32bit mode (I have some pre-beta UltraSPARC I hardware). This can be overridden, but leaves you vulnerable to a user land hack, which can hang the box.

Running at 167MHz these chips were hotish for their time, but compared to USII (now at a maximum of 480MHz) or USIII (just recently 1050MHz) they are rather slow. Every three years or so Sun rework the SPARC design to have better pipelines, better prediction, more TLBs etc. and speed increases in-between odd number releases are just fabrication improvements. Sun is a chip design company not a chip fabrication company.

It's hard to compare Itanium with SPARC, PA-RISC, PowerPC and Alpha - as far as I know there are no benchmarks in which is performs very well against modern 64bit RISC chips, Integer and particulary FP performance is generally considered rather inferiour.

The true test of a server class CPU is how well it handles cache coherency and memory latency issues on machines designed to support 8 or more CPUs. Itanium has not been shown to scale to these numbers. This may of course be because it's not yet been used in a server platform which supports that number of CPUs.

What I find particularly intriging is how Intel's marketing department is going to handle the clock speed differences in their product range. They have always used MHz as a marketing tool, but now they're going to have to concede that their prestigious server CPU is almost half the clock speed than that of their desktop CPU.

Re:UltraSPARC I

[fatphil]

"It's hard to compare Itanium with SPARC, PA-RISC, PowerPC and Alpha - as far as I know there are no benchmarks in which is performs very well against modern 64bit RISC chips, Integer and particulary FP performance is generally considered rather inferiour."

That's simply not been the case for the FP Spec benchmarks. For the latter half of the 90s HP and Dec were repeatedly trading the top spot on the table, and the x86 family realy didn't get a look in at all until recently, when about a year ago they came up with something which was nearly as good as a year-old alpha.

Even now, the x86 family is the 4th out of the major 5 families (power, alpha, sun, x86, pa).

Just look at
http://www.spec.org/osg/cpu2000/results/

Working with numeric computing - I actually use one of the benchmarking programs _every day_ - I find that the Spec banchmarks are very relevant to my world-view. If you know of other benchmarks that support your completely-disagreeing-with-SPEC view, then please post them here, so I can broaden my mind.

FP.