6 Jul
2009
6 Jul
'09
10:31 p.m.
On 6 Jul 2009 at 22:00, Ian King wrote:
The reason I'm so certain the ADM-3a was not
microprocessor based:
once upon a time, my (then) girlfriend came home to tell me that she
saw a dumpster in which some folks were dumping what looked like
computer boards. As it turned out, they were throwing away various
pieces/parts of ADM-3a's, including the circuit board that filled the
entire base of the unit. The ICs on that board were SOCKETED! I
pulled them all (bwah-hah-hah), and many are still in my collection of
TTL parts. As it happened, ONE of those boards contained a
lower-case-character ROM.
The ADM3A was deployed at an interesting time--microprocessors and
their peripherals were still pretty expensive and it's not clear that
much of a savings in real estate could have been realized.
Consider, for example, one of the terminals used frequently with the
MITS Altair and IMSAI 8080--the SWTP TV Typewriter. No
microprocessor, no LSI, save for a UART. It worked fine even with
those power-hungry 2102 SRAMs. A microprocessor version would have
been more expensive to build and probably not any smaller.
It didn't hurt that the ADM3A was an exceedingly dumb terminal.
Smart, page-editing terminals benefitted greatly from
microprocessors, even slow ones like the 8008.
On the other hand, when the LSI support chips came along, Wyse made a
small fortune offering cheap, fairly smart terminals using MPUs.
(was it an 8085 that they used in the WY50?)
--Chuck