IBM Preserves Memory Investments Across Power10 And Power11

May 21, 2025 Timothy Prickett Morgan

While the central processing unit inside every server gets all of the glory and much of the budget, these days it is the main memory that stores the data and gives that CPU memory that is perhaps more important and is actually the most costly part of the overall system.

This is particularly true of back office systems running relational databases, and increasingly these days, in-memory databases to speed up access to that corporate data. If you spend hundreds of thousands to millions of dollars on system memory, wouldn’t it be nice if that investment could be amortized over more than one generation of processor.

Well, with its OpenCAPI Memory Interface, or OMI, differential DIMM (D-DIMM) memory technology, which was first implemented in the Power10 processor, IBM is doing just that. We knew that the newer “Odyssey” cards, which are based on DDR5 chips and which deliver 4 TB of capacity per Power10 socket, will be forward compatible with Power11 chips and deliver 8 TB per socket on those future CPUs, and we talked with Bill Starke, distinguished engineer at Power Systems and the chief architect of the Power10 and Power11 processors, about this last December. What we did not realize is that the reverse is also true, which Starke explained in a briefing at the POWERUp 2025 user conference in Anaheim, California this week. He was referring to this chart, which we also saw when we talked to Starke last winter:

“By the way, you can plug in DDR4 to Power10. You can get a later Power10 and plug in DDDR5. You get a Power11, that’s going to come optimized for DDR5. Or, by the way, if you had memory in your old Power10 system and you want to carry that to your Power11, the Power11 is compatible with the DDR4. So it’s sort of, you know, depending on whether you need the extreme speed and performance or do you need something that’s just economically going to work better for how you’re running your financials and how you run your business with this technology agnostic approach. It’s a very healthy and sustainable way to do memory and provide the flexibility for your situation.”

We expected to be able to put “Odyssey” DDR5 D-DIMMs in Power10 as a kind of testbed for DDR5 D-DIMMs in Power11, but we did not expect for older “Explorer” DDR4 D-DIMMs to be pluggable into Power11. But, considering customers have bought many terabytes per system for many millions of dollars, it is a good thing for IBM to be doing this memory compatibility both forward and backwards.

We are a collector of IBM charts, and we also wanted you to see one we have not seen before, which shows that the high-end Power Systems and the System Z mainframes are using the same Explorer and Odyssey D-DIMM OMI memory cards. Take a look:

We wonder if the Power and Z memory cards are literally the same. We strongly suspect that they are.

One last thing: Starke confirmed that the plan was to get Power11 into the field in the third quarter of this year, which runs from July 1 through September 30.

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