AS/400 720 first steps

Disclaimer: I have code running on somewhere on that thing, but bitrot has taken a toll on my memory. (I last did OS development for the AS/400 back in 2000.) The 720 is an older system based on the "Northstar" CPU. Depending upon your model it is a PowerPC AS (64 bit PowerPC with some extensions) running somewhere between 200 and 260 Mhz. At the low end you get one CPU. The big monster we used to do TPC-C benchmark runs with was a 12-way. That particular CPU was an early multi-threaded CPU. To hide memory latency the CPU switches between two different register sets, probably on an L2 or L3 miss. (Or probably even configurable.) Other events can cause context switches too. If that feature is enabled on your model you will see logical processors instead of physical processors. (And this was a *very* early multi-threaded CPU machine. Probably one of the first commercially available at any volume. Not that AS/400s were ever high volume, but at its peak IBM was pushing 10s of thousands out a year.) It's a shame on the hard drives ... besides missing the OS the machine wants SCSI drives formatted to 520 byte sectors. And the OS is probably looking for a specific firmware level on the drives too, probably by using a SCSI inquiry command or a mode page. Obviously IBM drives from an AS/400 would work. There may also have been Seagate drives OEM'ed by IBM with the correct firmware on them too. (IBM dual sourced the drives, which was a good thing considering the fiasco that the next generation of drives caused.) I'm not sure where you get an OS for the machine. V4R3 to V5R1 should be fine. V4R3 will be faster; in V4R4 we started adding partitioning support via a hypervisor. You might find the OS but the license keys are the bigger problem. And IBM doesn't care about the hobbyist. A few people have them running - I'm surprised you are not getting more responses. -Mike