SMT PDP-8 (was Re: group buy for homebrew CPUs?)

Ethan Dicks ethan.dicks at gmail.com
Mon Aug 14 01:04:27 CDT 2006


On 8/14/06, woodelf <bfranchuk at jetnet.ab.ca> wrote:
> I think if you are building a replica is to design your own Flip/Chips
> and build a clean design from scratch. A PDP-8/S does not look that
> impressive, I know I seen one in the flesh once,as compared to a
> PDP-8/e. If you go with 20 I/O pins, (and sneaky pcb pinout )a simple
> GAL (SMT) could make up a generic card and be re-programmed for
> what ever logic you want.

Yes, but in the case of a Straight-8 or PDP-8/S, the R-series and
S-series logic is utterly incompatible with TTL.  The supply voltages
are +10V and -15V, and asserted logic is +3V or -3V, thus the reason
for staying with discrete SMT transistors.

The SMT GAL design could be useful for building an M-series machine
(-8/L, -8/i), but with that era of machine, the FLIP CHIP modules are
double sided, with 36 pins (32 signal pins and up to 4 power/ground
pins).

-ethan



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