TTL computing

From: Jos Dreesen <jos.mar_at_bluewin.ch>
Date: Wed Apr 10 14:01:38 2002

Tony Duell wrote:
>
> >
> > Playing aroud a bit with TTL using SSI parts, I get about 8-10 chips per
> > bit on the average for the alu. For 16 bit computer that is about 160
> > chips. I would say 1/3 more for control or about 250 chips total. Does
> > this sound right people with 16 bit TTL computers?
>
> IF by 'SSI' you mean just simple gates and flipflips ('74, '76, etc) then
> it sounds far too few.
>

If it's really SSI then it really is a low count.

Around '86 I build a 12 bit TTL based computer : 3 x 74ls181 as an alu, hardware
stack build around 3 2111 SRAM's and 8K main memory ( 2x6264's)
Total count : 85 TTL IC's ( MSI and SSI) and 5 SRAM's. It fitted neatly on 3
eurocards.

It used no microprogramming and no PROM's.
Building the same thing in SSI would have easily cost 6 times as much IC's.

It was, however, a bit lacking in I/O : it had 4 nixie tubes, but no serial or
parallel IO......

                                        Jos Dreesen
Received on Wed Apr 10 2002 - 14:01:38 BST