IBM's Power11 Processor Architecture
51 comments
·August 25, 2025sllabres
sillywalk
Nitpick: it's no longer iSeries, it's the unsearchable IBM i now. I believe it goes (System/38)->AS/400->AS400e->System i->iSeries->i5->i
> if one core of a processor in a x86 server dies, your server dies. This is not the case in the IBM Power environment.
I believe that having a spare processor core is new to POWER11. EDIT: No. I was wrong.
sllabres
You are right. I'm not working myself on these systems but they are often still called with their older name here due to the frequent renaming...
Regarding the processor: yes the processor spare is new to the Power11 but features like "Processor Instruction Retry" and "Alternative processor recovery" are older. Here are documents describing the feature for old 8284-22A (S822 with Power8 CPU) [1] or even older 8204-E8A (System Power 550 with Power6 CPU) [2]
[1] https://www.redbooks.ibm.com/redpapers/pdfs/redp5098.pdf (topic 4.3.4 and 4.3.5) [2] https://www.redbooks.ibm.com/redpapers/pdfs/redp4404.pdf
imglorp
Some are doing model inference.
https://wallaroo.ai/optimizing-ai-inference-and-governance-w...
jauntywundrkind
The memory improvement seems so so awesome. 3x the bandwidth, 2x capacity, via Open Memory Interface (OMI) buffers.
Really looking forward to x86 getting similar: Intel's MR-DIMM and industry standard MCR-DIMM are both sort of happening. Intel's Granite Rapids (Xeon 6900P series) for example takes either DDR5-6400 or MRDIMM-8800, a 38% increase. And which should also allow a capacity increase, up to 256GB dimms supposedly. But so far, seems like 96GB is as big as we get, and MCR-DIMMs are still work-in-progress. https://www.phoronix.com/review/intel-xeon6-mrdimm-ddr5 https://www.serversupply.com/MEMORY/PC5-70400/96GB/MICRON/MT...
fidotron
I can't be the only one that simultaneously appreciates that IBM are still in the game but remains mystified as to who is actually buying and using this stuff.
They simply have to have some farms in government running this to make it make sense.
CursedSilicon
On the low-end. Ever shopped at Costco? It's all IBM AS/400's handling the back-end. That's why all their Windows 11 PC's have big black and green terminal apps running front and center
On the high-end? Banks, airports, hospitals, research labs. There's a lot of places that need the kind of fault tolerance that specifically IBM POWER systems provide
EDIT: Okay, IBM POWER "systems". They've been described as mainframes to me so I went with that terminology
nabla9
IBM Z mainframes use Z processors and now Telum, Telum II processors, not POWER.
gosub100
I seriously doubt there's a POWER mainframe in the back of Costco to handle the 3 UPC barcode scans per second. It's possible that every Costco store funnels its orders to a single mainframe somewhere.
I think a more realistic case is the visa and MasterCard credit card networks that have almost 0% downtime.
CursedSilicon
Not a POWER Mainframe, no. But AS/400's come in many sizes. The smallest ones are roughly the size of a standard workstation
dardeaup
No such thing as a POWER mainframe. IBM's POWER lines (i and p) are different from their mainframe line (z).
chiffre01
I think it's more likely they have a rack of IBM iSeries servers in the back someplace, or maybe in a colo data center.
nxobject
For background to sibling comments - AS/400 aka "System i" was historically a separate line of processors, but is now POWER running a software translation layer.
https://en.wikipedia.org/wiki/IBM_i#TIMI
To illustrate why the AS/400 had its market niche, the Cali Cartel had a very successful installation of an AS/400. Apparently they used it to do both "business analytics" and back-office tasks.
https://www.vice.com/en/article/the-cartel-supercomputer-of-...
DebtDeflation
There used to be stories about small manufacturing companies that bought AS/400s in the early 1990s, installed them in their factories, then at some point there was construction and walls were built around them, and then they were discovered 20+ years later, still running, when they were upgrading their production lines and trying to figure out what was actually running them.
nine_k
Google used to use POWER9 chips, but they apparently have stopped.
I suppose the military should buy a significant amount, because they require 100% US-based development and manufacture.
sidkshatriya
Power chips are made by Samsung according to the article. The fab for that is probably in Korea.
dlcarrier
It's more beuroacracies in general than government in particular.
vb-8448
There are still plenty of IBM-I (formerly as400) and AIX installations around Europe.
Someone
The statistic to look at is not how many there are, but how many get sold nowadays.
Also, how does “plenty” compare to the millions (50 million or so, it seems from a quick search) x64s that Intel sells per year? Do they even sell 1% of that?
pram
People stuck on DB2 is the answer.
favorited
It was z, not Power, but I really enjoyed STH's recent video going through the design of the z17 mainframe with IBM folks: https://www.youtube.com/watch?v=C8oLfMXUo0U
russellbeattie
That was really interesting! All that proprietary hardware is mind blowing. The cost of those mainframes must be mind boggling, let alone the maintenance costs. It answers the question, "What does IBM do nowadays?"
But one thing I never knew about before was covered in just a few seconds in the video: 40+ layer motherboard PCBs. Holy cow, it was like a half inch thick! It makes sense now that I think about it considering how many components are slotted into it, but for some reason it never dawned on me that you could have a PCB that was so huge vertically.
doctorshady
I love working with the POWER ISA, it makes me happy to see they're still making high performance chips. I really wish these were more accessible to the average user though.
ChuckMcM
As a systems architecture dilettante I really like the Power architecture. It is old school super computer / mainframe architecture on a chip. Parallel processing architecture that makes cross domain inferences impossible etc etc.
A crazy friend of mine had a workstation with a Power10 main board in it running Redhat Linux. Other than the fact that it used what was essentially a rack server main board so had these 8 fans that blew through the chassis like a 747 on take off it was pretty neat.
SlowTao
Dont need a Power10 for that. Just get a Powermac G5 tower in a kernel panic and those fans will be flying!
bsder
Is there some technical limitation as to why IBM Power systems aren't leading the charge with AI? Or are the people using them just keeping really quiet that they have a superpower and not letting anybody know?
It seems like these systems should be stupidly good at AI training.
What am I missing?
MrDrMcCoy
Would love to have one in my homelab, but they're functionally impossible to acquire.
Keyframe
judging by the comments and (lack of proper) answers, the realm mystery is who are the customers?! Before, POWER excelled at bandwidth.. like real torrent of bandwidth. What's the edge these days?
JLO64
I hate phrasing a question like this, but I would genuinely like to know who the customer for this architecture is. My understanding is that cloud (and for that matter consumer) is all x86/ARM.
So is it science/defense that makes up their user base? I have an acquaintance who works at NASA mention that IBM stuff was really good for processing large amounts of data fast. Is that their primary advantage over other architectures?
doctorshady
Raptor Systems makes a bunch of ATX compatible POWER motherboards. As to who buys them, it's not entirely clear. If they were a little cheaper, I'd pick one up in a heartbeat. $3,000 for a CPU and motherboard is a bit hard to rationalize for what's effectively just nerding out though: https://www.raptorcs.com/content/base/products.html .
For the embedded market, NXP makes a bunch of QorIQ chips based around the POWER ISA - mostly for telecom products. These are actually reasonably common in certain devices, but not really what you'd want in a desktop.
TheAmazingRace
What's funny about all this is, back when the Raptor Blackbird MicroATX board dropped in 2018, you could cobble together one of those with a quad core POWER9 CPU for a reasonable $1200 out the door. Prices went up exponentially after the pandemic due to sourcing issues and some channels used for parts drying up. A shame, really.
I used to own one of these systems before I sold it to my dad, and I'm eagerly awaiting a next generation offering, if it ever comes out.
Palomides
raptor is still on power9 chips from 2017, I have one, but it's not a reasonable purchase unless you're a very very serious open source believer
doctorshady
My understanding is there's issues around POWER10 that stopped it from being adopted: https://www.talospace.com/2021/09/its-not-just-omi-thats-tro... . For me personally, having worked enough with embedded POWER chips to get weirdly comfortable with ISA, given the choice, I'd love to have a system like this to write pure ASM stuff on. Not for any practical reason in the slightest; pretty much in the same spirit of souping up a go kart.
On that note, out of curiosity, how do these compare with x86 and ARM chips from that era?
themafia
The last I checked most of the supporting mainframe systems use POWER. For example the DASD storage devices are all using POWER CPUs.
dlcarrier
It's customers that never migrated to x86/ARM.
wmf
IBM pulled out of the HPC market several years ago.
dmitrygr
mainframes
edit: thought some ibm mainframes used power in helper roles.
wmf
Besides the memory improvements these slides are really vague.
sillywalk
There was an earlier article that had more details[0]. And the Redbook for the High-End server[1] has a lot of information.
[0] https://www.servethehome.com/ibm-power11-launched-with-up-to...
[1] https://www.redbooks.ibm.com/redpieces/pdfs/sg248587.pdf
rbanffy
I get that the changes weren’t that pronounced between 10 and 11 in other aspects. I was really expecting more details on POWER12 this year.
russellbeattie
How are all the features of an architecture like this utilized? Does the hardware automatically take advantage of all the cache, RAM, threads, etc., or are mainframe applications specifically written with chunks of low-level assembly to optimize for the specific features of the chip and supporting hardware? The devs that write the compilers must be geniuses.
For those who have asked who runs this system: Power systems today run either "AS/400" aka iSeries, IBMs traditional Unix (AIX) or Linux (RedHat or SuSE).
In addition to the technical parameters mentioned in the article (an IBM Red Book would certainly provide more):
From what I know from conversations, SAP users are a large customers base for Power systems. I think the size of the possible main memory might be one reason, persistent main memory [1] could be another, in my opinion. But this feature is not new, it was available at least with Power 9. The systems are available with up to 64 TB memory (I don't know if all this memory would by available for one process, but from what I have read at least 32 TB is) and that seems to mix well with SAP HANA.
Another reason is licensing. LPAR partition is considered hard partitioning for Oracle databases, which makes licensing much easier and, in many configurations, also more cost-effective. [2]
Then there are several RAS features. Think of: if one core of a processor in a x86 server dies, your server dies. This is not the case in the IBM Power environment. These days many customers are happy with horizontal redundancy, but not all are equal.
[1] https://community.sap.com/t5/technology-blog-posts-by-member...
[2] https://oraclelicensingexperts.com/oracle-licensing-virtuali...