P
Pooh Bear
Keith said:Rob said:The PDP-8/I was fully-parallel, just like the PDP-8, except
that it was the first of the "-8" line to use TTL logic levels
(+3V & 0) instead of the negative ones (-3V & 0) used in the
Classic -8. [It was built out of "M-Series" modules, rather
than the "R/S/T/B-Series".]
Interesting stuff, indeed. I'm certainly not a DECie, so remembered
wrongly. ;-)
I thought TTL was +5V and 0. Or was this a later development?
The TI 74xx TTL series had a power supply of 5V and gnd (signal levels of
~3.6V and .8V), but that wasn't the only TTL ever to be done. IBM's
TTL, used in the 3080s, was +1.25/-3V with a signal level of gnd to -1.5V,
IIRC. TTL is a circuit topology, rather then a specific product.
BTW, most "TTL" wasn't. The later series ('S', 'AS', 'ALS', 'F', and even
'LS' were actually SDTL). My bet is that the DECs were DTL too, though
I'd love to hear more from Rob. ...maybe continue thos over on AFC.
Weren't the shottky ( and derived ) parts DTL input and TTL output ?
Graham