6 Aug
2015
6 Aug
'15
7:56 a.m.
On 08/06/2015 07:33 AM, Al Kossow wrote:
Main processor microcode is in RAM. Putting microcode
in ram and having
a small computer load it was actually pretty common in the 70's and 80's
in larger systems since then you didn't have to manage the hassle of
patching microcode in ROM.
Apple ended up putting a small TI microcontroller in the G5 because it
also couldn't boot on its own. There was a bunch of volatile state you
had to set up before it would fetch its first instruction.
And really big iron almost always had some sort of maintenance control
processor--some with their own mass storage. Have a separate, simpler
processor handle the management of a larger one made a lot of sense,
particularly when it came to diagnostic activity.
Think Cray, CDC,...
--Chuck