FPGA VAX update
pkoning at equallogic.com
Thu Nov 3 08:49:26 CST 2005
>>>>> "Chuck" == Chuck Guzis <cclist at sydex.com> writes:
Chuck> What surprises me about the home-built computers from scratch
Chuck> is the lack of imagination when it comes to architecture.
Chuck> Most are basically one-address-cum-accumulator designs. It
Chuck> would seem that larger register files are much easier to build
Chuck> nowadays and would open up the door to some 2 and 3-address
Chuck> I've always thought that 24 bits is a nice word size for a
Chuck> small computer. Divisible by 2, 3, 4, 6, 8 and 12 bits. An
Chuck> instruction could use 6 bits for opcode and 3 register
Chuck> addresses out of a 64 register file...
Some Philips minis had 24 bit words. I worked on one, can't remember
the model number. P2400? P9200? Psomething anyway. It had 8 sets
of 8 registers, one for each interrupt level, so there wasn't any
context saving overhead. No interrupt vectors either; you'd simply
load the interrupt handler start address into the PC of that level.
But still, a boring architecture by your definition: registers plus
one memory address, plus an index bit.
If you're going to go the 3 address route, it sounds like you're well
on your way towards reinventing the CDC 6000 architecture. And of
course that would be a fine thing to do -- if you're going to explore
computer architectures, what better path to take than the one first
walked by the foremost computer architecture genius of the 20th
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