IBM Is Running Out Of DDR4 Memory Faster Than It Thought
September 25, 2024 Timothy Prickett Morgan
Back in August, we told you about how Big Blue was shifting away from the DDR4 main memory chips and towards DDR5 main memory chips for Power10 systems, which were designed expressly to support both types of memory.
This is just like Power8 servers were designed to support both DDR3 and DDR4 memory, with the latter coming halfway through the Power8 product cycle. The Power9 machines used DDR4 memory solely, and the Power10 is getting support for DDR5 a little late in its cycle, given that we expect Power11 servers next year. Presumably the Power11 servers will just support DDR5 memory, given that the specification for DDR6 memory is still being drafted and is not expected to be ratified until 2025. But, it is possible that DDR6 could be retrofitted as a mid-life upgrade to Power11 systems.
In any event, as we told you back in early August, in announcement letter AD24-0474, most of the new DDR5 memory features for the Power10 lineup were available on July 19, except one feature for high-end machines coming on August 13. IBM warned at that time that on November 12, all DDR4 memory features for the Power10 line would not be available for orders of new machinery and would only be available for upgrades on existing systems.
Now, in announcement letter AD24-2116, IBM says you better bust a move, because DDR4 memory cards for Power10 iron will actually not be available after October 22 instead of the original November 12 cutoff date.
In general in systems, if you mix and match memory, everything gears down to the slowest speed, so having a mix of DDR4 and DDR5 memory doesn’t make a lot of sense, given that DDR5 memory is more expensive, runs faster, and has lower latency. So even if IBM would permit this, it would not be an economically or technically sound idea. But, then again, if you have invested heavily in DDR4 memory and still have some memory slots available in the machine, you might want to shake a leg and buy the DDR4 memory now before you can’t. Even if IBM is still allowing for customers to buy memory upgrades for DDR4 cards, that doesn’t mean that these will not eventually run out, too.
It is always a bit tricky to give good advice about memory configurations in Power Systems iron. If capacity was the only concern, you would populate half the memory slots with the fattest memory sticks based on the fastest memory technology that would go in the system, and then at some future date when you needed to boost performance, you would populate the other empty slots. But doing this means sacrificing half of the memory bandwidth of the system until you fully populate the memory slots. So customers often buy the skinniest and cheapest memory they can afford and fully populate the slots so they are at least getting full memory bandwidth. But, when they need more memory capacity, they have to swap all of the memory out and buy a whole new round of fatter memory. Which is an expensive upgrade indeed, considering that memory is the most costly part of a back office system and has been for many years now.
If you need DDR4 memory for a Power10 machine in the future, it may be tough to get on the secondhand market, but once Power11 machines are launched some time in 2025 and Power10 iron is being taken in trade by IBM Global Asset Recovery Services (or whatever it is called now that the used equipment is managed by the Power Systems division) and the other secondhand system peddlers in the world, then supplies should be a little more available. IBM strips down and recertifies each and every component in a machine it takes in trade and puts it in the barn and sells components separate from base system configurations, for instance. Other secondhand dealers can break down systems and sell components, but they can’t certify them “as new” like Big Blue can.
The point is, if you have a Power10 machine using DDR4 memory, take a moment and think about what you might need in terms of adding memory capacity or bandwidth in the coming year or two and don’t let this slide.
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