Ars Dissects POWER5, UltraSparc IV, and Efficeon

Burton Max writes "There's an interesting article here at Ars about the POWER5, UltraSparc IV, and Efficeon CPUs. It's a self-styled "overview of three specific upcoming processors: IBM's POWER5, Sun's UltraSparc IV, and Transmeta's Efficeon. " I found the insights as to Efficeon (successor to Crusoe) to be particularly good (although it paints a sad picture of Transmeta, methinks)."

Comments

Good article

[The_Ronin]

Too bad they focused too much on Power and Transmeta while paying little time on UltraSparc IV and V and ignored Itanium. Needs a little more balance and it would have been a great read.

Re:Good article

[AKAImBatman]

I think it would have been best to have an article devoted to the TransMeta chip, and split the Power5/UltraSparc discussion out into its own article. That way he could have given a great deal more attention to the powerhouse chips and how they're going to change the future. TransMeta's chips are on the level of ARM, not UltraSparc.

One Power 5...

[Realistic_Dragon]

Will show up as _4_ processors to the OS! (2 cores both doing SMT.)

This means that in a (say) 512 processor box the OS will have to handle 2048 processors efficiently. That's placing a lot of control in the hands of the software designers, and a lot of money in the hands of the companies that license per processor.

On the other hand, UNIX is getting pretty efficnelt at scaling to large systems, perhaps it (and by extension Linux thanks to SGI and IBM) will be able to handle it with no problems. One thread per processor on a desktop system might prove to be quite efficient :o)

power consumption

[bigpat]

Wasn't low power consumption the number 1 benefit that transmeta was looking to provide, so that you could get twice the battery life (or soemthing like that) without sacrificing too much performance. Did Transmeta shoot itself in the foot by letting people think that it was going to provide higher performance chips than the competition.

The main selling point of transmeta was always power consumption, so have they lost their edge in that area? If so, then that would be serious for them, but the article doesn't answer that question.

So, despite being lower voltage/MIPS...

[csoto]

the author suggests that it's not worth "pissing off Intel" to go with Transmeta. Give me a break. Transmeta is the only thing pushing Intel to make Centrino and other lower-wattage chips. They recognize that anybody in the mobile computing/devices world will seriously consider anything that gives their customers increased battery life and less toasty pockets.

memory and processor watts not the same

[pz]

Multiple times while reviewing the Efficion architecture the article's author suggests that the tradeoff of additional storage required for Transmeta's code-morphing approach will easily balance out the power savings from making a simpler CPU. This belies a deep misunderstanding of power consumption in digital systems, as readily evidences by the fact that modern non-Transmeta processers dissipate multiple tens of Watts of power (often nearly 100W) and a full complement of memory (4G, in modern machines) dissipates a few Watts at most.

Also in the article, the author suggests that processors spend most of their time wating on loads, and then argues that since the code-morphing approach means more instruction fetches, the Efficion processor will be spending disproportionatly more time on loads. Then, after this assertion, he admits that he does not know *where* the translated Efficion code is held. Might it be in one-cycle-accessible L1 cache? That point is conveniently sidestepped. He does not understand under what circumstances the profiling takes place, although he regurgitates the sales pitch nicely. He argues that transistors hold the translated code (trying to argue against the transistors-for-software tradeoff) but then does not realize that transistors in memory do not equate transistors in logic (neither in power, as they are not cycled as frequently, nor in speed characteristics).

In all, I find the author's treatment of the Transmeta architecture sophomoric, and, after finding that section lacking, I left the rest of the article unread. Your mileage may vary.