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Military Time 2901

Gene Cash

originally, why i don't know.

360-67 had high-resolution timer option .... 13-some mic. version for use in accounting and time-slice.

cp67 would stuff value for something 50millseconds at location x'54' and then do an overlapping mvc instruction for 8 bytes ... i.e.

mvc x'4c'(8),x'50'

the current value of the timer would be moved to location x'4c' and the value in the location x'50' timer reset to the value at location x'54'. the elapsed period was then calculated by the difference in the value at location x'4c' and the original value loaded into x'50' (fairly consistent value kept at x'54').

there was an oscillator and a timer "tic", i.e. access location x'50' and tic the current value, aka the timer would tic and then attempt to update location x'50' (waiting for access to the memory bus). if the hardware timer tic'ed again while there was a pending update to location x'50' from a previous timer tic ... the machine would "red light" (i.e. machine check).

we ran into this with a project mentioned in recent post

The dissolution of Commodore 2902
Charlie Gibbs Yes a sad tale indeed. Irving Gould and Mehdi Ali milked Commodore and the Amiga dry. However I think it is hardly likely...

project at the university when i was an undergraduate building a clone controller; aka reverse engineer the channel interface and build channel interface board for a clone terminal controller. in one of the early tests ... we, in fact, caused the 360-67 to machine check ... because the channel interface board held the memory bus for too long a period (blocking timer tic update of location of x'50').

The dissolution of Commodore 2903
I like to think that part of the problem was that the heads at Commodore didn't think so either. I picture them sitting in their...

there was article someplace blaiming four of us for plug-compatible (clone) controller. misc. other posts mentioning it

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The dissolution of Commodore 2902

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Military Time 2900