pdp 10 - How was concurrent programming achieved on the PDP-10?

A useful way to do concurrent programming is, say, a Compare-And-Swap instruction, which really is two operations, executed one after the other, atomically. This was available on the IBM 370 and on the 68000 as CAS, (and on later x86's as cmpxchg, but not on the PDP-10 as far as I can tell.The PDP-10 also allows an interrupt to occur part-way through one instruction, so there's no guarantee that even one instruction is atomic. Yet, they were sold and maintained in ASMP configurations, and in other multiprocessing topologies as well I expect, so...Read more

pdp 10 - What are the differences between the various 36-bit computers from DEC?

I want to ask about thePDP-6PDP-10various implementations KA-10, KI-10, KL-10DECSYSTEM-20What are the differences between these? I'm not that interested in architectural differences, cache sizes, etc. I'm most interested in the differences that could feasibly trip up an assembly language programmer.Things like the instruction set, register set and so on, how these varied from machine to machine.Bonus points if you also include the Foonly machines and other clones....Read more