1 Feb
1999
1 Feb
'99
12:25 a.m.
At 09:19 PM 1/31/99 +0000, Tony wrote:
Yes, I've never seen a schematic or prints of such a TTL computer, but
would love to.
I actually have some hardware now, the one from Don Tarbell, without
documentation.
Yes many systems were done with just transistors in a "small" system too. A
block diagram seems simple, it is all the control and glue logic that got
out of hand for my design. I didn't use a 74181 by the way, as couldn't see
the use of most of the functions besides A and B, A+B, !A, etc. Just
building an equivalent to a 74181 with only 7400 gates or valves would use
quite a lot (I haven't counted them).
-Dave
Am amazed you
could build a computer like this with ~400 cards ~800 tubes.
That is similar to building a complete computer with 200 SSI TTL chips like
a 7400. Especially since a 24 bit latch could use 24 of the cards. I tried
This doesn't sound out of line. The CPU of the PDP8/e on my desk is 3
quad cards of TTL, mostly simple gates. Perhapes 250chips total. OK, some
of them are more complex (like full adder circuits), but there's nothing
that big in there. a design once (on paper) with MSI ic's like
74193 counters, and it quickly
got out of hand, 100's of ic's.
If you're going to allow anything in the TTL data book, then you can
trivially make a CPU in 200 chips. You have to cheat slightly (74181
ALUs, small PROMs, etc), but it can be done. It has been done - many times.