FPGA VAX update, now DIY TTL computers
Stegeman, Henk HJ SITI-ITIBHW5
henk.stegeman at shell.com
Tue Nov 8 03:41:58 CST 2005
I fully agree with you. Building your own CPU is really an exciting project.
I took me more then 3 months to debug my 110 TTL CPU with
256 words of micro code of 48 bits.
See: http://www.anysystems.nl/hjs22.html for some pictures and the
I build this CPU & IO unit in 1976. A liitle bit younger then the
Elektor machine :-). Do you still have the Elektor machine ?
Regards Henk Stegeman.
> What surprises me about the home-built computers from scratch is the
> of imagination when it comes to architecture. Most are basically
> one-address-cum-accumulator designs. It would seem that larger
> files are much easier to build nowadays and would open up the door to
> 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
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
TTL based, with a shiftregister based memory. (6 or 8 512x2
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 !
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