powerpc vs itanium vs x86 performance

ensabah6

hi,
is there a reason that powerpc and itanium have been unable to outperform the x86?
apple had the g3, g4, g5 and at times claimed powerpc and risc outforms the pentium,
and intel itself bet that itanium epic would outperform the x86, and have lower power consumption and replace the x86.

what went wrong?

mgb_phys

Itanium might have had a chance if everybody had been willing to rewrite their software for it's novel instruction set. As it turned out writing the compilers was a lot harder than anyone thought and it's speed advantage wasn't enough to warrant the effort. It does outperform a Xeon in floating point, which unfortunately is completely irrelevant for most customers. It's now really an orphan product line, it only has one real customer and is a couple of generations of fab technology behind the cutting edge.

The PowerPC is trickier - it does outperform the x86 in the areas that matter to it's customers = performance/watt. It is the basis for an awful lot of embedded systems as well as being the heart of the Xbox and PS3

ensabah6

DO you think Intel would have been better off with Alpha Risc rather than Itanium Epic?

Why couldn't Apple G5 then be offered in a laptop? (the speculation is the reason apple switched to mobile core 2 duo) benchmarks I've seen show G5 lagging core 2 duo.

jtbell

I seem to remember it was because they couldn't make one that ran cool enough, but I could easily be wrong because it was some years ago.

ensabah6

I'm aware of that claim, but powerpc RISC was supposed to offer much higher performance per watt than archaic x86

ibcnunabit

Maybe they should have called it the LOW-PowerPC....

morris.hoodye

I've done performance testing on both x86 & itanium. I wrote integer math algorithms in C & C++ then used native compilers for each platform. The x86 with no special optimizations outperform the Itanium hands down.

ensabah6

So how does HP sell Itaniums? Why does anyone want to buy itanium?

I don't deny that G5 could not fit in a notebook but given it uses legacy free RISC, why couldn't IBM engineer a G5 lower power cpu for Apple?

mgb_phys

Nobody cares what CPU is in their server. They care that it is certified to run the OS/Software and that somebody will support it.
HP picked Itanium, because Intel convinced them (possibly with some financial inducement) that it would be the next big thing and they would have a head start over DELL or IBM. HP also had a problem at the time of having three proprietry processor families in house after buying Compaq.

Not while also giving it the same processing power as a Core2duo for the same price for a single customer.

ensabah6

I know that Itanium FPU is world class. How well though does Itanium FPU compare to a hypothetical Sandy Bridge/Fusion x86 + GPU

Wasn't the whole argument for RISC is that it is legacy free unlike x86, and therefore scales better? ARM can offer processor and performance and battery power consumption unmatched by x86 at the low end.

Do you think ARM cortex a9 + tegra is a credible competitor to x86 say in the netbook arena?