RE: Omnibus TSC8-75 schematic?

[Rick Bensene]

Eric Smith wrote:
> 
> If a schematic isn't available, but a unit was made available on loan to
> reverse-engineer, I'd be willing to do it. 

At this stage, it appears that no original schematic for this board has been 
uncovered.

Efforts are currently underway to reverse-engineer an actual TSC8-75 board and 
derive a useful schematic. It is hopeful there will be something available 
relatively soon.  

The particular board being reverse-engineered has a serial number of <700, so 
it will not have the ESME IOT implemented, but it has been discovered that ETOS 
does not require this IOT in order to run properly.   ETOS will run slightly 
more efficiently if the board supports the ESME IOT (6365), but it will still 
run just fine on the boards that don't have the feature.

I'll try to post updates here as the project progresses.

It is my hope to be able to construct a functional equivalent of one of these 
boards, and get ETOS running on my physical 8/e system.   The biggest challenge 
is going to be replacing the pesky SP380A (12 used on the board) and SP314A 
(one used on the board) chips used for Omnibus interface, but there's a lot of 
discussion in the mailing list archives about replacements that seem to work , 
so it shouldn't be too difficult.

-Rick

Re: Omnibus TSC8-75 schematic?

[Paul Anderson]

Hi Rick,

Call me if you can.

Paul
217 766 7690

On 10/28/15, Rick Bensene  wrote:
> While there are documents out there that describe the function of the
> Educomp/Quodata TSC8-75 Timeshare System Controller for Omnibus PDP 8
> machines, I have searched high and low, and there doesn't seem to be
> /any/ schematics for it anywhere.
>
> I know this was a proprietary board that did some pretty interesting
> things to trap IOT, JMP, JSR, and HLT/OSR instructions on the PDP
> 8/e/f/m/a machines and provide additional capabilities versus DEC's
> Memory Extension and Timeshare Control board.
>
> I have a fantasy of being able to run ETOS on real PDP 8/e hardware, but
> I don't have one of these boards, and they seem to be pretty much
> unobtainium.
>
> There are a few of them out there, but obviously, the owners of these
> aren't in the mood to submit them for reverse engineering.   Perhaps
> someone out there has already done this, or someone has documentation on
> the board that may include schematics that simply hasn't scanned it yet.
> Bitsavers comes up with nothing under the DEC archives, and there's no
> sign of Quodata or Educomp folders.
>
> I have read the descriptions of the function of the board, and the IOTs
> that make it do its things, but I just don't have the expertise on the
> guts of the Omnibus PDP 8 machines to be able to take this information
> and create a design for a board that performs these functions.  I've
> also looked at the code in SimH that emulates the functionality of the
> board, but again, it isn't enough information for me to be able to
> figure out how to implement it in hardware.
>
> In any case, I think it'd be interesting to see if one of these boards
> could be reproduced.
>
> I've found some old ClassicCMP list archives that mention some stuff
> about ETOS documentation and folks that worked for Educomp/Quodata that
> were involved in the creation of ETOS and this board, but the thread
> died over 10 years ago.
>
> I am probably wishing for something that doesn't exist, but I figured
> I'd ask anyway, as maybe someone has stumbled across some of this stuff
> and just hasn't made it public yet.
>
> Rick Bensene
> The Old Calculator Museum
> http://oldcalculatormuseum.com
>
>
>
>
>
>
>
>

Re: Omnibus TSC8-75 schematic?

[Eric Smith]

If a schematic isn't available, but a unit was made available on loan
to reverse-engineer, I'd be willing to do it. Recently I
reverse-engineered a schematic and the firmware of a Zendex ZX-200A
Multibus floppy disk controller, which replaces both the iSBC-201
single density controller and iSBC-202 double density controller used
in Intel MDS systems:

http://www.brouhaha.com/~eric/retrocomputing/zendex/zx-200a/zx-200a.pdf
https://github.com/brouhaha/zx200a-fw