What's the difference?
The Power6+ chip does have one important distinction, according to documents I have cadged from inside Big Blue. The Power6 chip had a total of eight memory keys (seven for the kernel and one for the userspace for applications), while the Power6+ chips have a total of 16 memory keys (eight for the kernel, seven for userspace, and one for the PowerVM hypervisor). According to the IBM documents, the additional eight memory keys "help prevent accidental memory overwrites that could cause critical applications to crash."
Presumably, this sort of thing is not happening on prior Power5 and Power6 chips that do not have the extra memory keys. And by talking about this as a key feature in a press release last October (if IBM had admitted the chips in the machines were Power6+ and brought up the topic), it would have been a delicate matter to bring up that the older chips didn't have them.
I can't help but believe IBM had a lot higher hopes than this for the Power6+ chip, but without Big Blue making statements publicly about its plans and without more current roadmaps, it is hard to say what happened between early 2007 and late 2008. And IBM is happy to keep us all guessing.
And Handy was not interested in talking about the possibility of a real clock crank on the Power6+ chips before the octo-core Power7 chip is delivered in early 2010 using a 45 nanometer process. Handy gave the standard "you know I can't talk about unannounced products" when I asked about this. But then again, it seems that IBM doesn't always talk about announced products, like the Power6+ chips plunked into several Power Systems machines last fall.
It seems likely that IBM will do something to boost clock speeds on the Power6+ chip in the fall and get it into every machine in the lineup. (The 64-core Power 595 is still using Power6 chips and is still running at 5 GHz). The pressure on Big Blue to do something will come through the quad-core "Tukwila" Itanium arriving from Hewlett-Packard and Intel, which was pushed out to mid-2009 as this year was getting rolling. Tukwila is a year or more behind schedule, just like Power6 was and Sun Microsystems' 16-core "Rock" UltraSparc-RK chip is at least a year behind, if not more.
If by some miracle of accounting Sun Microsystems or Oracle - if the $5.6bn acquisition of Sun proceeds as planned - get the "Supernova" servers using Rock into the field and they show good benchmarks, it would not be odd to see a Power6+ Power 595 suddenly appear running at 6 GHz. But the real pressure will likely come from below: four-socket and larger boxes using Intel's future "Nehalem EX" octo-core chips.
Ironically, these are made by IBM as well as others. And then there's the "Istanbul" six-shooters from Advanced Micro Devices that will eat into the Power 570 and low-end Power 595 space too - if IBM isn't careful. If there is even a slight delay with Power7, IBM will crank up the Power6+ clocks and hope customers can take the heat.
Anyway, we'll keep you posted Tuesday on whatever Power6+, er, Power6 machines IBM debuts as part of this Dynamic Infrastructure blitz. Don't expect to see any pluses in the press releases or spec sheets. They probably won't be there, unless Big Blue realizes that when you don't tell customers what is really happening, it looks like you are hiding something. And if you look like you are hiding something, in my experience, that usually means you are. And sooner or later, people find out what. ®