Power 7: Lots of Cores, Lots of Threads
Published: August 3, 2009
by Timothy Prickett Morgan
With the global economy still faltering and its biggest i, AIX, and Linux shops putting the brakes on spending not only just because the economy is bad but also because they are starting to think about the future Power7 chips and what they may have to offer, IBM has to do something if it wants to keep Power Systems sales from crashing. In fact, it needs to do two things, and now the company has done both of them.
The first thing, and perhaps the most important thing, was to guarantee companies that buy Power6 and Power6+ iron today will have an upgrade path into the new boxes. There is no CIO or IT manager on earth who is going to shell out hundreds of thousands to millions of dollars on a new Power6 or Power6+ server today when they know Power7 machines are coming out in the next year--unless they know there is an upgrade path that will protect the serial numbers and therefore the investments they make in that Power6 and Power6+ iron. And so IBM did something for the high-end of the Power Systems line that it did when the Power5+ machines were running late in 2006 and the Power6 machines were expected in early 2007 (and also running late): it guaranteed an upgrade path.
Back in May 2006, the upgrade protection was only given out for the high-end 32-core System p 590 and 64-core System p 595 machines, not the 16-core System p 570 models and not officially at least the System i counterparts to those boxes. Back then, IBM said it had looked at the accounting rules, which are pretty strict about how many components can be replaced before you can't call it an upgrade, and would offer upgrades from Power5 and Power5+ versions of these machines to the then-future Power6 boxes.
This time around, IBM is telling customers who have Power 570 (which have up to 16 cores in Power6 variants and as many as 32 cores on Power6+ versions) or Power 595 boxes (which have as many as 64 Power6 cores) that they will have upgrade paths into the future Power7 machinery, which is due in the first half of 2010. For Power 595 machines, Scott Handy, vice president of marketing and strategy for the Power Systems division, says that the upgrade process will involve swapping out Power6 boards for Power7 boards (which IBM called processor books) during the course of planned downtime and patching the AIX 6.1, i 6.1, or Linux operating systems to take advantage of the Power7 chip's features. The Power 570 machine, which uses processor cards with the CPU and memory on smaller cards, will have a slightly different two-step process, but enough of the components of the original Power6 and Power6+ iron will remain in the box that IBM can preserve serial numbers.
Preserving serial numbers is important for the company bean counters. All server hardware and software is on a depreciation schedule, and if you get rid of a server by swapping it for a new one, you have to write off all the investment in the server at the time you move it out of the data center. But if you do an upgrade that preserves the serial number, you add the incremental investment onto the existing depreciation schedule. Equally important, IBM doesn't charge the full price for a Power7 system when a Power6 machine is used as the base and then upgraded. IBM has to make the numbers work out so customers who get to Power7 in two steps don't pay a hefty premium for spending now rather than waiting until 2010. In fact, to my way of thinking, given the economy, IBM has to give some pretty big discounts on those future Power7 servers and nail down the rough parameters of pricing on these boxes to get anyone who is a serious negotiator to even sign a deal now. So be tough at the table, people, because a new processor architecture should mean better bang for the buck, not just more bang.
This situation is nearly exactly parallel to the situation three years ago, except this time it includes 570-class boxes and the i platform is also covered. The other difference is that IBM is talking about the Power7 chip to show off its prowess with chips as Intel has had to delay the quad-core Itanium "Tukwila" Itaniums from their late 2008 delivery to early 2010 and it looks like Sun Microsystems has killed off the 16-core "Rock" UltraSparc-RK processor and its related Supernova systems ahead of Oracle's expected takeover of Sun this summer. With Hewlett-Packard so dependent on Itanium for HP-UX sales and Solaris customers not knowing what to think until Oracle finishes the Sun deal and puts out some product roadmaps, IBM can sell a lot of Power6 and Power6+ iron if customers know they have an upgrade path directly to Power7. And IBM has to talk about its plans for Power7 anyway, because Intel's eight-core "Beckton" Nehalem EX family of chips, due by the end of the year and in systems early next year, are no joke, and neither will Advanced Micro Devices' 12-core "Magny-Cours" Opterons be a laughing matter. These machines, based on these two X64 behemoths, are aimed right at the Power 570 and the low-end of the Power 595 lines. IBM has to blunt the attack, and that is another reason why it is giving out some details about the future Power7 chips.
Up until now, about the only thing anyone knew about the Power7 chip is that it was being implemented in a 45 nanometer process and, thanks to confirmation from Ross Mauri, general manager of the Power Systems division last year, it would have eight processor cores.
On July 21, just before The Four Hundred took a summer break, Handy said that the Power7 chip, in fact, would come with variants that have four, six, or eight cores and that each core would have as many as four processor threads per core. So a single Power7 chip could have as many as 32 different processor threads, compared to four threads with the Power5 through Power6+ generations of chips. (The Power4 and Power4+ chips did not support simultaneous multithreading, but were the first chips in the world to have two cores on a die.) IBM has not said how far it will scale its Power7 servers, but if it does 32 sockets as it does today with the Power 595 (and given the statement above about upgrade paths, this stands to reason), then a future 595-class box will be able to support 256 processor cores and 1,024 threads.
That large thread count is one of the reasons why IBM will officially support up to 1,000 logical partitions per Power7 system, up from the maximum of 254 with Power5 through Power6 machinery. IBM techies told me ahead of the Power6 launch that the chip was able to support over 1,000 partitions, but Big Blue did not allow that many to run because of processor capacity limitations.
The Power7 chips will have on-chip DDR3 main memory controllers, and the faster memory speeds will help get processors and main memory back closer together if IBM keeps the clock speeds of the Power7 chips between 3 GHz and 4 GHz, as expected. Current DDR3 memory runs at 1.07 GHz and 1.33 GHz, and will soon be running at 1.66 GHz. The DDR2 main memory used in Power5 through Power6+ iron runs at 400 MHz, 533 MHz, 667 MHz, and 800 MHz. That's arguably too slow for a processor that is getting close to 5 GHz in clock speed or just hitting it, as the Power6 and Power6+ chips do, depending on the server.
Two more things.
One: When the Power Systems division was created out of the converged System i and System p product lines back in 2007, IBM said that it was looking at bringing Live Partition Mobility to the i5/OS platform, not just keep it on the AIX platform. Live Partition Mobility, and its companion Workload Partitions (WPARs) or Live Application Mobility, would be very useful features for a Power6-to-Power7 upgrade. AIX shops will learn this, but i shops won't. AIX customers who want to move to Power7 machines will be able to take an extra box they have and move their running workloads off a box they want to upgrade using Live Partition Mobility, then power it down, add the Power7 books, put on the patched AIX 6.1, and move the workloads back onto LPARs running on the Power7 box. The i shops that want to move to Power7 boxes are going to have to do it the old-fashioned way by either having a high availability cluster of production and backup machines, upgrading on half of the cluster at a time, or do a backup, upgrade, restore three-step.
Two: AIX 6.1 and i 6.1 will get patches to support the Power7 chips, and then AIX 7 and i 7 will follow the new Power7 iron to market (presumably with lots of new software features) about 90 days or so later.
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