24 Jul
2006
24 Jul
'06
7:20 p.m.
On 7/24/2006 at 9:09 PM Brad Parker wrote:
If it's interesting, the MIT CADR has a 32 bit alu
using the 74181 and
uses the '182 for carry. The schematics are also on bitsavers. It's a
reasonably general microcoded 32 bit cpu. Not bad for it's day.
If it's a 20 bit CPU that the OP wants, perhaps someone has a set of prints
for the PERQ.
I've always been fascinated with the TI 74S481--a 4 bit slice in a 40 pin
package, but with a lot of functionality inside. I don't know if they're
unobtainium nowadays. The 1978 TI patent on it is here:
http://www.freepatentsonline.com/4224676.html. One curious aspect is the
"position" input pin: if the slice is the most significant, you put a
voltage higher than 3.6v on it; if the least significant, less than 0.8
volts; if in the middle, between 1.8 and 3 volts.
Cheers,
Chuck