One of the stories I heard about the 50 is that if you threw it into the ocean it would sink intermittently.
Anyway the 50 was the first computer I was paid to program on. Many were bought to run in 7070 emulator mode as the 50 was the smallest / cheapest machine that could run 7070.
Happily I was on the 360 side.
At another shop, we had 2 50s, one running DOS and the other OS with HASP.
One day a student was having trouble with the Test and Set (superceded by Compare and Swap) instruction not setting the condition code properly. I wrote a short diagnostic program to exercise TS, store the resulting condition codes and dump. The instruction was not performing correctly.
I showed the dump to the non IBM engineers who hemmed and hawed. A couple days later one phoned me up to say that TS wasn't setting the condition code correctly - exactly what I had been telling him.
They fixed the problem. The next day I got a phone call that HASP wasn't starting on the other 50. Took a dump and found HASP was in a wait just after TS.
The engineers had swapped microcode cards between the two machines.
No. The 50 was subject to intermittent failures (whether microcode or hardware I don't know).
SYNCH is how user mode exits are called from supervisor code.
COLT (Canadian On Line Teller) often ran (runs?) in supervisor state and in the bank I was working at the time would initialise a transaction buffer by setting it to all one's - very bad news when that buffer address was erroneously set to zero because some registers were not preserved across pseudo reentrant (a particularly repulsive term) interrupt points.
This invalidated all the New PSWs triggering an interrupt cascade such that the STOP key would not work because the instruction never completed. SYSTEM RESET (courtesy the IBM engineer) did the job.
> At another shop, we had 2 50s, one running DOS and the other OS with HASP.
Nowadays it's worth mentioning that that "DOS" has nothing to do with MS-DOS/PC-DOS on PCs (or any other DOS on any other microcomputer where the names may coincide).
The release dates of the IBM PC and System/360 being closer together than the IBM PC is old today, and the mainframe world being so secluded from mainstream computing, I wouldn't be too surprised if someone thought there were s/360s with an "A:\>" prompt on a teletype somewhere. :)
To the rest of the story, I cannot find the original quote no matter how I search (I'm sure it's out there, Google has just become increasingly worse lately), but I remember a story in a single paragraph of someone who contacted CDC or IBM or whatever, about a seemingly misbehaving instruction. The engineers replied that this was curious, as the instruction in question was usually one of the more stable instructions. That day, the person asking learned that apparently, machine code instructions can be ordered by reliability.
Anyway the 50 was the first computer I was paid to program on. Many were bought to run in 7070 emulator mode as the 50 was the smallest / cheapest machine that could run 7070.
Happily I was on the 360 side.
At another shop, we had 2 50s, one running DOS and the other OS with HASP.
One day a student was having trouble with the Test and Set (superceded by Compare and Swap) instruction not setting the condition code properly. I wrote a short diagnostic program to exercise TS, store the resulting condition codes and dump. The instruction was not performing correctly.
I showed the dump to the non IBM engineers who hemmed and hawed. A couple days later one phoned me up to say that TS wasn't setting the condition code correctly - exactly what I had been telling him.
They fixed the problem. The next day I got a phone call that HASP wasn't starting on the other 50. Took a dump and found HASP was in a wait just after TS.
The engineers had swapped microcode cards between the two machines.
My manager was not pleased with the engineers.