3 Nov
2005
3 Nov
'05
6 a.m.
What surprises me about the home-built computers from scratch is the
lack
of imagination when it comes to architecture. Most are basically
one-address-cum-accumulator designs. It would seem that larger
register
files are much easier to build nowadays and would open up the door to
some
2 and 3-address designs.
The reason is the effort it takes......
Ask anybody who actually made a CPU ( I myself did a 12 bit
TTL based, single address single accumulator machine).
The real effort is actually building and debugging the unit.
There is only so much time you have....
I've always thought that 24 bits is a nice word size for a small
computer.
Much too big to actually build in TTL.
In 1974 Elektor magazine started a series of DIY articles that described
an extensible ( 12 bit or 16 bit width ) three address, clockless
computer.
TTL based, with a shiftregister based memory. (6 or 8 512x2
shiftregisters .)
An expensive extra wasa 2102 based RAM.
The machine did hardware multiply and divide +
Instructions were build into the address map .i,e, address XX is the
adder, adress yy is a shift and so on..
The start of this series actually predates the Mark8 computer !
Jos Dreesen