Enter the IBM z17 mainframe with Telum II (more clues for Power11?)

IBM is announcing their new z17 mainframe, based on the Telum II (see our notes on the original Telum CPU). IBM first announced the Telum II last year and the z17, its intended first deployment, has now emerged just about bang on time.

Still, we're obviously more interested in Power ISA around here, and IBM has yet to say much substantive about Power11 other than the usual assertions of additional power efficiency, more cores and higher clock. It is also expected to offer DDR5 support for enhanced memory bandwidth, though this is all but certain to require OMI DDR5, not direct-attached RAM as in our Raptor boxes. But it's often instructive to look at what's going on with IBM mainframes for microarchitectural clues now that Z-machines and IBM "big" Power chips often have the same underlying design.

The first Telum strongly emphasized cache. Interestingly, it did so by dropping categorial L3 and L4 altogether: instead, IBM developed a strategy where cores could reach into the L2 of other cores and treat that as L3, and reach into other chips' cache and treat that as L4. Each chip had eight cores and 32MB of L2 per core, giving lots of opportunity for more efficient utilization. The picture of the Telum II die above shows that IBM has not substantially deviated from this plan, using the same 128K/128K L1 but increasing L2 to 36MB per core. IBM's documentation says that there are eight cores per chip, but at a cursory glance there appear to be ten on the die, likely for yield reasons (two cores would be fused off). Assuming these dud cores still have useable cache, however, that matches IBM's specs of up to 360MB of effective L3 and a whopping 2.88GB of L4 per system.

The cores top out at 5.5GHz with various microarchitectural improvements such as better branch prediction and faster store writeback and address translation, all the typical kinds of tweaks that would also likely show up in Power11. Power11 is also expected to remain on 7nm with a "refined" process instead of moving to 5nm. (It's possible that Power12, whenever that arrives, may skip 5nm entirely.)

Of course, the marketing material on z17 is all AI all the time. IBM's claimed AI improvements seem to descend from an enhanced "DPU" ("data processing unit") with its own 64K (32K instruction/32K data) L1 cache capable of 24 trillion INT8 operations per second, the kind of bolt-on hardware that could also be incorporated or scaled-down into other products. In fact, such a product exists already, shown above: IBM's Spyre Accelerator, which is basically 32 more DPUs. These attach over PCIe and would be a good alternative to our having to scrabble around with iffy GPU support, assuming that IBM supports this in Linux (but they already do for LinuxONE systems, so it shouldn't be much of a stretch).

If you have the money and a convenient IBM salesdroid who actually answers the phone, you too can horrify your electrical utility starting in June. As for those of us on the small systems side, Power11 in whatever form it ends up taking is not anticipated to emerge until Q3 2025, presumably as what will be the E1100 series starting with the E1180 and going down. This further shrinks the production and sales window for the long-anticipated Raptor S1 systems, however, and there hasn't been a lot of news about those — to say nothing of what the Trump tariffs could mean for rolling out a new system.

Plan 9 finally comes to the POWER9

A great announcement today from the 9front team: ongoing support for ppc64. Today's release finally brings the groundbreaking Plan 9 operating system to our platform as a preferred architecture, with big endian a first-class citizen. It's idiosyncratic, sometimes baffling and at times deliberately outright user-hostile, but now you have a choice of operating systems and can truly use our refreshingly different computers with a refreshingly different user interface paradigm. I'm downloading and installing it on the Blackbird right now and I'll report back with a full review in detail.

Also, I'm well aware of the calendar, thanks.

Real-world Blackbird does real-world stuff for Apache (really)

Let's call it a #ShowUsYourTalos moment. This video from Savoir Technologies shows off their own Blackbird system, carrying an 8-core POWER9 CPU with a 3U HSF, a 4-slot NVMe riser card, two 64GB DDR4 DIMMs and a 500W PSU running on the onboard ASPEED framebuffer.

But this machine isn't just a bragging rights toy: it provides substantial support for the Apache products Savoir works on. These are primarily Java-based and there are three main choices for JDKs on POWER9, in particular Adoptium's Temurin, Eclipse OpenJ9 (descended from IBM's original J9, which I personally run on my AIX POWER6), and Red Hat's build of OpenJDK. Savoir tests on all three.

As anyone working on Java will attest, it's not enough just to make sure it works on different JVMs. This machine is dedicated to improving ppc64le support, stability and performance actually on the architecture itself. (Linus would agree.) Savoir does multiple builds to tamp down broken unit tests and find glitches due to Power ISA's different memory model guarantees. One example they cite in the video was a stress test they did on this very box, running one billion SOAP requests through Apache CXF with no errors.

I'm not involved or linked to Savoir in any way; I'm just delighted to see real hardware in the real world doing real things for real people. Right now, I don't think you're going to get throughput like this from anything with the current crop of RISC-V chips in it, and I'm hopeful that S1 is still in the pipeline to give us the shot in the arm we need to stay ahead of the curve on open hardware.

Microwatt goes multiprocessor

It's been awhile since we dropped in on Microwatt, the OpenPOWER VHDL softcore. Microwatt now runs on multiple FPGA boards or can be run (slowly) in simulation, and is capable of booting Linux. Raptor uses Microwatt for the Arctic Tern soft BMC. Although it still doesn't support vector instructions, recent commits have added an FPU and many of the standard special-purpose registers, and the newest ones now add support for SMP.

The newest pull request, currently to be committed, allows more than one processor core to be created by adding an NCPUS option to soc.vhdl. These cores can be debugged separately with JTAG and have the same view of memory and the same timebase value, and can be individually activated. For interrupts, they each have their own presentation controller in the XICS.

Although Microwatt cores are currently of only modest performance, more cores — if you have the space — can certainly improve its throughput and the range of applications it could be practical for. Unfortunately, we've still yet to hear anything new about the Solid Silicon S1 or how libre Power11 will end up being. Hopefully as the Microwatt design gets more efficient, at least the very smallest Power ISA systems will now have some additional flexibilities to work with.

Fedora 41 mini-review on the Blackbird and Talos II

It's Fedora upgrade time again! And in the same way I preface all these mini-reviews (see our last for Fedora 40), Fedora was one of the first mainstream distributions to support POWER9 out of the box, it's still one of the top distributions OpenPOWER denizens use and its position closest to the bleeding, ragged edge is where we see problems emerge first and get fixed (hopefully) before they move further downstream. That's why it's worth caring about it even if you yourself don't run it. Also, as always, recall both my Talos II and Blackbird are configured to come up in a text boot instead of gdm and I start the GUI manually from there. I always recommend a non-graphical boot as a recovery mechanism in case your graphics card gets whacked by something or other, and on Fedora this is easily done by ensuring the symlink /etc/systemd/system/default.target points to /lib/systemd/system/multi-user.target.

I'll also give a quick shout out here to Dan Horák at Red Hat, who responds to our user issues and maintains some additional Fedora packages in copr. Read his newly updated blog for information.

Irritatingly, dnf continues to fail to update grub2's config (bug 1921479, showing messages like 0ed84c0-p94177c1: integer expression expected during the process), so the process remains largely unchanged from F39 and F40:

dnf upgrade --refresh # upgrade prior system and DNF
grub2-mkconfig -o /boot/grub2/grub.cfg # force grub to update
dnf install dnf-plugin-system-upgrade # install upgrade plugin if not already done
dnf system-upgrade download --refresh --releasever=41 # download F41 packages
dnf system-upgrade reboot # reboot into upgrader

Again there was no installation screen on either the Blackbird or T2 this time around; for both systems I needed to log in as root on an alternate VTY (Ctrl-Alt-F2 or as appropriate) and either dnf system-upgrade log --number=-1 intermittently to watch the updates, or just do journalctl -f if you want a live feed and don't mind the scrollspam. You can probably also still monitor it on the virtual TTY in the BMC web interface. Both systems then rebooted (fast reboot is disabled on both) and came up clean, again with no XFS burp on the T2! I think we can conclude the updated Petitboot firmware has resolved that issue. As usual, one more grub2-mkconfig -o /boot/grub2/grub.cfg was needed to get Petitboot's menu looking right and the install was complete.

I should also note that two people on the Raptor forums reported that their systems were unbootable after this update. However, both the Blackbird and the T2 upgraded with no hitches except for a really old F33 package on the T2 I had to blow away, so I can't replicate that here and neither can Dan.

Let's proceed with testing out the Blackbird, which is my proving ground system before upgrading my regular T2 workstation. The biggest update is that in the most recent kernel versions, especially if you haven't done any updates between the F40 upgrade and now, we finally have 1920x1200 support on the built-in BMC HDMI video!

Yes, much as it pains me to say it, Wayland has finally progressed to the point where it's useable with the ASPEED BMC framebuffer. This is a crucial point to make if you're running a GPU-less configuration, especially if you're trying to achieve a fully libre machine with no firmware blobs: you can now use Wayland with it with little obvious compromise, if you really really want.

All resolutions up to 1920x1200 are supported, including 1920x1080. This works in both GNOME and KDE Plasma 6.2, though I'll have something bad to say about GNOME in a moment.

Now, there's still reasons not to use Wayland with BMC graphics, and the big one is that the fans just ran continuously in Wayland because everything is getting crammed through llvmpipe. This is a little 4-core Blackbird and it could keep up with it, but it certainly earned its money doing so. When I switched back to Xorg using plasma6-x11-unsupported, all was quiet again.

X11 modelines never had any problems supporting BMC video, but here it is for the record.

I also commented on the Chromium build now available for ppc64le in the F40 mini-review, so it's only fair to see how far it's come. And, well, it's come a long way. Many more things work and the previous graphical glitches in Xorg seem gone now. It's still somewhat rickety and crash reports pop up intermittently as its subprocesses fart and die, and really big Wasm apps like (oh the irony) Google Earth will bring it to its knees, but casual browsing largely works fine and it can run MAME from the Internet Archive's online arcade now with reasonable performance. I still find my personal builds of Firefox with Baseline JIT to be faster with browsing and I retain my philosophical objections to Chrome and Chromium, but I can't deny the progress, so this will make others of you happy.

Something that won't make you happy was GNOME. Whether it was Wayland or Xorg, there were tons of graphical artifacts on the blob-free Blackbird (these are photographs of the screen since the framebuffer didn't always reflect the issue):

The Plasma 6.2 update doesn't seem to break anything major, so if you're blob-free, I'd just use KDE with the unsupported X11 support. It's easier on the cores and it generally works. Xfce would probably be okay too.

On the T2, other than that weir-dass F33 remainder package, the upgrade was similarly smooth. Nothing so far has seemed to regress. However, the Talos II has a Raptor-BTO AMD WX7100 card, unlike the Blackbird.

Regular readers know very well I'll complain when it's time to complain, but this time around the F41 upgrade worked well and the system seems solid. I'm sorry to hear about the problems some others have had, but I couldn't replicate them here. So far this has been one of the smoother updates, which was a profound relief.

CHRP support gone from Linux kernel

UPDATE: The patch has been retracted, see comments.

There weren't that many Common Hardware Reference Platform PowerPC systems anyway, but if you have one of them (notably systems like IBM's RS/6000 7046 Model B50, the Total Impact briQ, Motorola PowerStacks or the PegasosPPC or Pegasos II from Genesi), your days are numbered as CHRP support will be removed from the next Linux kernel release. CHRP never got much market traction; Apple, then the largest seller of PowerPC machines, only partially supported it (Old World Macs are sui generis and New World Macs are a combination of CHRP and PReP), and as a result Linux support for Power Macs — at least what remains — never completely depended on it.

At least for the Genesi machines, however, you have better and more supported options in MorphOS and AmigaOS 4, and while Power Macs should still work, they're (IMHO) more usefully served by one of the BSDs. For the real oddball machines, though, if you were running a bleeding-edge kernel this is the end of the line — unless you'd like to step in and maintain it.