On 16-Feb-16 16:04, Nelson H. F. Beebe wrote: > Will Senn <[email protected]> asks on the list on Tue, 16 Feb 2016 > 12:47:12 -0600 about CDC operating systems. > > > The CDC [67]x00 family CPUs have no interrupts: instead, there are > several peripheral processors (PP's) that interface to external > devices such as disks and serial terminal lines. The PP's are 12-bit > computers, each with 4096 words of memory. They communicate with the > main CPU by monitoring a couple of privileged memory locations that > hold data for a device operation. At our site, the PPs were never > accessible to end users, so no one outside the computer center ever > knew their instruction set. > > http://ygdes.com/CDC/60141900_Codes_Rev-A_May65.pdf
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