Cray J90 emulation page

Welcome to the Cray J90 emulator. Below you can see the status of the emulation engine. If it is running, you can connect to it, using one of the following methods:

Use user name crayusr and password seymour for guest access. Once you log in, you'll see a message detailing how to get a personal account should you need one.

If you want to read about the story of this simulator or leave comments, check out this site:


Q: What is available on the machine?

A: Right now the machine runs Unicos 10. It has the language tools installed as well (C/C++/Fortran/ASM). On top of it, I've compiled some open-source programs for the platform: bash, mc, wget and lynq

Q: How can I get X11 working

A: X forwarding should be functional over SSH. Under Windows, I use MobaXTerm, under Linux it should 'just work'

Q: How can I exchange files with the machine?

A: Mainly ftp and wget. You can connect to the FTP server running on the simulator to transfer files or use wget on the machine to access HTTP (not HTTPS!) servers.

Q: How fast is the emulation?

A: Hard to tell. The reported MIPS rates above vary quite a lot. That is due to the fact that checking the real-time-clock in the emulator is extremely slow. Luckily that happens - mostly - in the idle loop of the OS. In idle each emulated processor executes somewhere around 7 million instructions a second. If I start a CPU-intensive stress, the number jumps up to about 43. This is compared to the real system running at a 100MHz. From that alone it would appear that the emulator less than half as fast as the original system. One also has to take into accound though the fact that a processor can't issue an instruction every cycle. I don't have IPC numbers for the J90, but my hunch is that it has not been much higher than 0.5. This is due to the apparent lack of branch-prediction and the rather low data-cache hit-rates. Overall, it might be that a real system would not feel much faster in everyday use than the emulator. Floating-point heavy vector code is a different topic though: there the real system should beat the emulator handily. Also keep in mind that the emulator you're using here is a dual-core system, where the smallest J90 sold had 8 processors.

Q: How can I run the system myself?

A: You can't, unless you have a copy of the OS and a lot of free time on your hand. I don't have the rights to distribute the OS image, so while you can download the simulator sources and binaries, you won't get the virtual disks you would need to run things. Even if you did have an install CD for UNICOS 10, it takes a lot of tweaking and changing to get the OS over to the emulator. This is because the SWS (the Sun workstation that was used as the maintenance console for the original machines) is not emulated at all and the install media depends on its existence a lot. If you want to go down that path, contact me and I can help you - after all I've done that - but it's not as plug-and-play as one would expect.