There are rumors floating around that IBM plans to buy Sun. A few friends and I discussed the effects on Twitter.
cwhitney: I kinda like the IBM + Sun idea. That actually works, although it would then be basically SunBM versus HP versus genericroSoft.
jauricchio: I’m in favor of hitting ZFS, DTrace, and OSol with the GPLHammer. I’m not in favor of axing Rock and Niagara. You know it’s true.
cwhitney: They would have a stable of old but mission critical ($$$) unix OSes too. GPLv3 Hammer is a no for me (you do want OS X ZFS?)
jauricchio: It’d be v2. THEY want it in Linux.
cwhitney: Rock and Niagara may go away, but a future of Sun arch guys + PPC team + actual in-house fab = fun times.
jauricchio Not stoked about POWER5, 6. Niagara and Rock broke more notable architectural ground.
cwhitney: Most certainly but most all the non-embedded, non-x86 CPU arch work comes from those teams. IBM also still has fabs, unlike most
djcapelis: You mean unlike… AMD? :( Yeah it would be interesting to see them together. I would hope for people to jump between them more.
cwhitney I understand the $ reasons, but that AMD move was dumb. Losing vertical integration = bad.
I’m very pleased by Sun’s work in architecture. Niagara and Rock are both bold experiments. At a time when most of the chip vendors were just starting to realize single-threaded scaling was going to get harder, Niagara threw away single-thread performance for radical parallelism. For the workloads Sun targets (network serving, mostly), that turned out to be a very, very good trade-off. These days you can get a 4U with 256 hardware threads and 512GB RAM. That’s a lot of threads. Matched with Sun’s reliably solid memory systems, that’s some pretty serious multi-thread performance.
Rock is something out of a research paper. Somebody finally built a hardware transactional memory system? Suddenly all those papers become relevant to the real world! I’ve got more to say on Rock, but that’s another column. Let’s just say it’s a Good Thing.
On the other hand, IBM’s architecture team hasn’t impressed me lately. The POWER6 looks like a solid chip, but it’s just more of the same: all the old tricks with bigger numbers.
- Two-way SMT is good.
- The semi-shared L2 looks like a cute idea: if you have up to four threads working intensely on the same data, you can fit up to 8MB in their L2. Without semi-sharing, you’d only get the same speed for 4MB between two threads. That wider and larger sharing could squeeze some more parallel speedup out of code that can be parallelized but still contends for the same data. To put everything in the right places, you’d need a good scheduler that can see the coherence patterns.
- The L3 is huge! 32MB? What is this a, PA-8800 Mako?
- Clock speeds are ever higher. Anybody running lots of POWER chips doesn’t care about power and heat: they’ll just put a little more in the budget for their new supercomputing center. Because of who they sell to, IBM is in some ways immune to the general purpose computer power/heat crunch. The first wave of the crunch (laptops and desktops) only hit Intel, AMD, and IBM’s PowerPC. The second wave (datacenters) is hitting everyone but the POWER team. At least, that’s sure how it looks from where I’m standing.
Pretty much the only things I find interesting in POWER6’s architecture are the semi-shared cache and the retreat to shallow in-order pipes. Even that latter was foreshadowed by Niagara and the Cell/Xenon.
Don’t get me wrong: I’m not trying to belittle the POWER6 in any way. It’s a great work of engineering. I’m just not impressed with it as research. In contrast, Sun’s doing research with every processor they make. If IBM does buy Sun, I really hope they let Sun’s architects and chip engineers keep doing their thing. The best future, as Chris said, is Sun’s creativity on IBM’s resources.