Originally Solaris; SunOS was on much earlier hardware. These days also Linux and NetBSD.

There are some slightly more modern forks of Solaris, but I lost track of which ones are still active and maintained.

If it has any of the fancy 3d cards, or PC compatibility cards then you almost certainly would need to stick with Solaris for drivers.

keenerb wrote on 2025-01-24, 05:43:

Did it originally come with Solaris?

Yes, almost certainly 7 or 8.

Are there modern Linux distros that would work with it?

Modern - probably not, but it should be easy to find something from the era, or slightly later.
Also, some BSD systems.

OS/2 or WinNT builds?

They never supported Sparc.

Heres the support page for NetBSD:

https://wiki.netbsd.org/ports/sparc64/

Debian Sparc64 port:

https://wiki.debian.org/Sparc64

The older, 32bit Sparc target on Linux was dropped a while ago, it seems.

I believe Solaris 9 was the last version to work on U5/U10.

Hints
U5 and U10 are basically the same motherboard in different form factor cases. (the RAM slots on the Ultra 5 are limited to 128Mb, as the 256Mb sticks are too tall to fit)

Note that the onboard IDE has poor performance. Every system I've worked on had disc mirroring off two SCSI devices with the IDE drive limited to holding a third copy of the metadb data (yup, a 8.4 or 9.1G disc left holding 100Mb of data).

If you are thinking of swapping CPUs, note that range of motherboards were installed - there isn't complete interchangeability between motherboards and CPU modules - refer to the Sun field engineer's guide.

I would also recommend upgrading the openboot PROM (OBP) to the latest release - you may have a chicken and egg situation where you can't boot from CDROM because of the OBP, and can't upgrade OBP cos the CDROM doesn't work (Hint: netboot the OBP upgrade binary).

mdog69 wrote on 2025-01-25, 11:15:

I believe Solaris 9 was the last version to work on U5/U10.

Solaris 10 should be the highest that will work. It's listed on the HCL. Link below. I think some versions of 11 "MIGHT" work. If you check the notes, the last update for 11 removed a lot of older CPU support. but the U5/10 are certified for Solaris 10.

https://www.oracle.com/webfolder/technetwork/hcl/index.html

Solaris 10 may well work, but you'd really be pushing it. I run Solaris 9 on my Ultra 10 and its not exactly fast - if I had Solaris 7 or 8 media I'd probably run that instead.

keenerb wrote on 2025-01-24, 05:43:

Did it originally come with Solaris? Are there modern Linux distros that would work with it? OS/2 or WinNT builds?

Solaris 7 most likely. An effort to port Windows to SPARC was announced but as far as I can tell it never got far. OS/2 was never in consdieration - IBM attempted to port it to their own PowerPC hardware but gave up on it shortly after doing the bare minimum preview releases to satisfy contracts they'd signed.

LInux, NetBSD, etc, will run on it. But the 7zip benchmark puts my 333MHz Ultra 10 as being about the same speed as a first generation Raspberry Pi, so I guess that may give some idea of how useful running Linux on it will be. Better off running Solaris IMO - at least thats something a Raspberry Pi can't do better (yet).

You could even pick up a SunPCi card on ebay and have a go at running Windows:

UltraSparc is too new for NeXTStep/OpenStep for Sparc.

Most modern Linux distributions have become too bloated to be useful without several Gb of RAM. Any modern web browser is out of the question for the same reason.

Solaris is certainly going to be the best operating system for the platform.
NetBSD is a good choice for any platform that is no longer well supported by Linux.

Solaris 8, 9 or 10 would be the OS to run on one of these if you want something period correct and matching the oddball hardware. If you want to use it for something practical (i.e. have it accessible online), NetBSD is the modern OS to go for.

In any event it's good to have the fastest CPU and a decent amount of RAM. Solaris never really flies, but this is about as good as you can get it for Solaris 9. For 10 you should consider an upgrade to 512MB. Getting a bit rusty on my Sparc lore, but if you want to run a SunPCI card, that will determine OS version. The original SunPCI (with K6-2) is supported up to Solaris 8. You can get it to run on 9, but it's non-trivial (I did that for no good reason about 20 years ago, don't ask me how). The SunPCI II is supported up to Solaris 9 and SunPCI III can run on Solaris 10. I don't think the combination with the Ultra 5 is supported though.

Interesting tidbit: earlier Sun systems were heavy stainless steel chassis tanks, but these systems marked the point when Sun outsourced it to Taiwanese ODMs, more specifically Mitac, who also built for the likes of Compaq and Packard Bell at the time. This use of consumer-grade manufacturing was panned in a similar way to the PowerMac 4400. However, this has one big advantage a few decades on: Sun used coloured plastic on earlier SparcStations that has deteriorated to the point of crumbling (the purple bits on SparcStation 5 and 10, for example). Mitac used more generic ABS which has yellowed terribly - but retains much of its structural integrity.

dionb wrote on 2025-03-05, 21:44:

The original SunPCI (with K6-2) is supported up to Solaris 8. You can get it to run on 9, but it's non-trivial (I did that for no good reason about 20 years ago, don't ask me how).

Yeah, my Ultra 10 is running Solaris 9 so I had to jump through those hoops. IIRC it involved creating a bunch of symlinks, and installing the latest solaris patch cluster. Without the latest Solaris patches it sort of appeared to work, but windows tends to crash when loading the desktop and it doesn't render text correctly.

I've also heard the IDE interface in the Ultra 5/10 isn't great performance-wise. I added a SCSI card and hard disk to my machine, so the IDE interface is only used for the CD-ROM drive now. Of course you can't just go putting any SCSI card in these machines - I stole a card out of my Blade 1500 that it wasn't using.

I use OpenBSD v7.6 (no X) on mine currently, after replacing my clock chip. Previously, Solaris 10u8 with CDE ran well, but relatively slow, with 512MB memory. My hard disk is a 60GB Seagate IDE.

Back in 2008/2009 when I got an U5 I purchased Solaris 8 2/04 ( last version of 8 ) for Sparc. I also tried OpenBSD.

I think you can use bigger SIMMs if you remove something that is in the way (floppy drive maybe don't recall).

I also installed a bootable UWSCSI PCI card and a SCSI drive to make the system snappier since the built in IDE port is slow.