Dual Mace

GregMansfield wrote Mace for the CDC6000 series computers. It cleaned up a lot of junk in Scope, CDC's official OS.

PurdueComputingCenter latched on to Mace and pretty much made it their own. VicAbell? knew Mace through and through. He tweaked the scheduler regularly, always upping the monthly job count as a result. DualMace was his masterpiece. It scheduled jobs among three processors, two in a 6500 and one more fast one in a 6600.

The CDC also had ten PeripheralProcessors (PPs) which did all the system work, including I/O. JimBesemer tells the story of learning to program the CDC. Reading the assembler manual he had found one I/O instruction, PAGE, which would start output on a new page. He thought surely this would be handy should he ever find a way to produce output in the first place.

Of course how to do I/O wasn't written down anywhere. The skill was passed on father to son. DaveDodson taught me how to do I/O by waking up a PP and passing it a CircularBuffer. CDC programs buffered output within the user's address space. This was particularly un-handy when a program crashed. You got all of your output except that in the buffer. This is the exact opposite of a LogicAnalyzer which gives you only what's in the buffer.