three interesting Omnibus Cards

[gnupublic]

Today I got two OMNIBUS cards for memory (16k and 32k) and a very interesting serial card with three interfaces. I know nothing about the manufactor. Every hint and probably documentation is welcome.

16k word:


32k word:



An at least the serial card with three UARTs (Intersil IM6402-1 IPL)



Have fun,
Volker

 

[BitWiz]

Nice looking boards. May I ask where did you find them?

 

[m_thompson]

The third board has 3x UARTs, so that could be useful.

 

[gnupublic]

May I ask where did you find them?

My source is an old man in northern Germany who has plenty of parts. I will try to help him selling some of his stuff.

 

[Terri Kennedy]

Today I got two OMNIBUS cards for memory (16k and 32k) and a very interesting serial card with three interfaces. I know nothing about the manufactor. Every hint and probably documentation is welcome.

16k word:
View attachment 1298094 View attachment 1298095

32k word:

View attachment 1298096 View attachment 1298097

Cool! Did DEC ever offer anything other than core memory for the PDP-8 line?

Since the 32KW board is only half-populated, does that mean 64KW was possible? Or was it just "board full of 4K parts is 16KW, board half full of 16K parts is 32KW"?

 

[ftcnet]

Cool! Did DEC ever offer anything other than core memory for the PDP-8 line?

Yes, but only for Omnibus (and newer) models. ex:
MS8-A (quad) 1K, 2K, 3K, 4K
MS8-C (hex) 16K, 32K
MS8-D (hex) 32K, 64K, 96K, 128K

 

[DougIngraham]

Since the 32KW board is only half-populated, does that mean 64KW was possible? Or was it just "board full of 4K parts is 16KW, board half full of 16K parts is 32KW"?

Not with a quad width board unless it also has the MMU onboard. The 16k board uses 4k x 1 drams. The 32k board is half populated with 16k x 1 parts. It looks like they used an Intel dram controller chip. The 4k and 16k chips have almost identical pinouts making this a fairly easy conversion. The 4k parts were probably considerably cheaper at the time this board was designed or they would have just populated it with one row of the 16k chips.

The official extension beyond 32k requires additional signals found only on one of the hex board extra connectors. It also requires a different MMU than the M837. To be specific you need an M8416 to control the M8417 (32k dynamic) or M8418 (128k dynamic). These are hex boards and need the handful of hex slots found in the 8/a.

 

[gnupublic]

You mean this cards M8416/M8417:







Do they work together with /e CPU? or do they need /a CPU? I have a 8A620. (20 slot backplane double PSU with 8/e CPU.)
I can get two more if anybody is interested.

Have fun,
Volker

 

[DougIngraham]

You mean this cards M8416/M8417:

Yes, those cards.

Do they work together with /e CPU? or do they need /a CPU? I have a 8A620. (20 slot backplane double PSU with 8/e CPU.)
I can get two more if anybody is interested.

I am pretty sure they will work with the KK8E CPU. I don't remember seeing anything that would indicate an issue.

I believe there is a version of Fortran that knows how to generate code for beyond 32k but I have never used it. And my M8418 has a problem where the onboard switcher doesn't come up because there is a short in one or more of the DRAM chips on that supply. I am going to try to supply power externally and watch the chips with a thermal camera. Hopefully the bad chip(s) will get warmer and show me what needs to be replaced. It might also be possible to discover the issue with a current probe.

 

[ftcnet]

Do they work together with /e CPU? or do they need /a CPU? I have a 8A620. (20 slot backplane double PSU with 8/e CPU.)

Yes, the KT8A works well with either CPU. The 8A backplane 'E' connector has the 4 Bank Select signals (32K per bank). Neither CPU uses the 'E' connector Bank Select signals.
The latest version of OS/8 had some support for 'above 32K' memory as well as the WPS (Word Processing System) software.

 

[m_thompson]

The 8A backplane 'E' connector has the 4 Bank Select signals (32K per bank).

These 4x signals are Wire-Wrapped on my 8a systems, and one of them has a sticker that says "KT8A Compatible".
It might be worth checking your 8a backplane before you try the KT8A.