Single-board TTL PDP-8 (was Re: pdp-8/i ECO history?)

Ethan Dicks ethan.dicks at
Wed Oct 20 10:49:59 CDT 2010

On 10/20/10, Vincent Slyngstad <vrs at> wrote:
> From: "Ethan Dicks": Wednesday, October 20, 2010 8:14 AM
>> On 10/20/10, Vincent Slyngstad <vrs at> wrote:
>>> Hmm.  I might choose the 8/L for something like that.  Possibly soup
>>> up the memory to 32K, but leave out all the option cruft of the 8/I
>>> backplane.
>> And replace the 7453 and 7482 with something made with less unobtanium?
> Sure.  We've talked about how to do that before, I think.  You'd face that
> problem starting from either the 8/I or the 8/L.

Yes, but I thought it worth keeping in play.

>> The memory extension hardware to take it over 4K is obviously
>> non-trivial in size (especially considering it doesn't fit in an -8/L
>> CPU enclosure).
> Good point.  You would definitely need some board area for that.

Considering how much of the -8/i backplane it takes up (about 1/2 as
much as the EAE), it's a noticable chunk.

>> OTOH, if you have over 32K
(*have over 4K)

>> there might as well be provisions for OS/8-compatible mass
>> storage, otherwise it's just a papertape machine with more than 4K.
> True, though an RF08 emulation doesn't take much board space.

Nope.  That takes about 3"x5" in TTL (with a 16-bit Dallas RAM/battery
module), IIRC.

> Or one could go with an RX08 interface for extra clanking ambiance :-).

While amusing and handy for some (I would use it), unless someone
whips up a cable-compatible RX01/RX02 emulator (could be to floppy or
removable FLASH), there are only so many original drive sets running
around.  Of course, one could build that RX01 emulator and include an
optional Arduino-based MP3 player to emit the whirring and clanking.
Frivolous but entertaining.


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