20 Oct
1999
20 Oct
'99
10:15 a.m.
Allison wrote:
ok, By discrete you meand transistors and diodes.
An 8080 cpu would likely fill a rack 20-25" high with boards.
IIRC, the 8080 was about 4000 MOSFET transistors. If you implemented it
with individual FETs, and packed it densely, I think you could fit it in
a 10.5" high rack space easily, and a 5.25" high rack space with difficulty.
Of course, you'll need plenty of forced air cooling. From a serviceability
point of view, building it less densely is clearly better.
If you implemented it with bipolar transistors configured as saturating
logic, it would require perhaps twice as many transistors and a lot more
resistors for TTL logic, or 50% more transistors, a lot of diodes, and a
lot of resistors for DTL logic.
In many respects the 8080 is a far more complex CPU
and would
be significantly bigger. It would also be slow compared to the NMOS part.
Even in TTL-equivalent logic, it would be faster than the NMOS part if it
was designed reasonably well.
If you want blazing speed, build it with non-saturating logic like all the
early IBM 7000-series machines. That's equivalent to ECL. Now your
talking about a huge amount of power consumed and cooling needed.