I fear you are right. I had thought there would be *someone* who knew, remembered something, or could look it up. I had that thought also. I have some logic handbooks, and have Googled like mad, but no luck. I did manage to largely exhaust the possibilities related to PDP-8/i peripherals and options, so it is starting to look likely that they have nothing to do with the 8i they came with. I put a description of them on alt.sys.pdp8 some time back. I'll attach it at the end of this message. that Yeah, I had similar thoughts, along the lines of how incredibly rare and valuable they must be if no-one has ever heard of them. Perhaps I have the only 24 in existence :-)? Still, if they aren't used *for* anything, there may not be much demand for them. Vince Here's that description from alt.sys.pdp8: On Tue, 7 Oct 2003 18:43:35 +0000 (UTC), cdl(a)deeptow.ucsd.edu (Carl Lowenstein) wrote: OK, I pulled a couple out of storage to look at. The form factor is your standard single-wide flip-chip stuff that the 8i and 8L are made of. There are four transistors near the purple handle, with four resistors in the center separating them into two pairs. Then there is a row of four TTL chips; 7440, 7474, 7402, 7474 from left to right. Next is a row of 2; a 7402 and a 7400. Next is a row of diodes and resistors. Lastly, two more TTL chips, a 7400 and another 7402. Each TTL chip has the standard .01 bypass cap, and there are assorted resistors and diodes here and there, too, There are three small electrolytics, one on each edge of the row with the diode and resistor grouping, and another on the right edge of the second row of TTL. Both side 1 and side 2 of the edge connector are extensively used, as opposed to the simpler cards where only side 2 has fingers. The one that is marked M750A has a cut trace going to what I think is N2. The M750B is missing that trace, but has an oversize finger there, as if someone thought they might need to solder to it. On the other hand, the M750A has an oversize finger at what I think is R1, but on the M750B there is a trace there that seems to go to one of the 7402s. The rest of the component layout, resister values, etc. between the two versions is virtually identical. Hope that helps! Vince

Ed wrote: Thanks to someone on the list who may not want to be named, I've scanned a photocopy of the 13-JUN-1991 Edited Option/Module Hardware List. A ZIP of a PDF file is available at: http://www.brouhaha.com/~eric/retrocomputing/dec/doc/oml/ Be forewarned that the file is 165 megabytes. I'd actually much prefer to send out copies on CD-R for a nominal amount of money to cover media and postage, since bandwidth costs me money. I know various people out there have other editions of the OML. Earlier ones would be nice since they'd have more complete coverage of early machines. However, thus far no one else who has one has been willing to make it available to be scanned. I tried OCRing a few pages, and the results were not useful. According to the OML, the M750 is a Line I/O Control, equivalent to two W750s, and was used in the PDP-8 family.

thanks Eric! I still have not found mine... I think the one I had was from the 80's some were thee has to be a tape out there with the info..... it would be a wonderful thing to have an online database..... dream dream dream... oh well someday! ed! ----- Original Message ----- From: "Eric Smith" <eric(a)brouhaha.com> To: "General Discussion: On-Topic and Off-Topic Posts" <cctalk(a)classiccmp.org> Sent: Monday, November 17, 2003 6:19 PM Subject: Re: DEC M750 flipchip?

I brought up the box of these from the basement again to try to find a year of manufacture. No luck, though I did notice stamps on them that say "tested 251", "tested 201", or some other number, whatever that means. I imagine it identifies an individual, rather than a date. I did note that most of my M750As appear to have had the transistors in the upper right replaced (there is rosin around the pads). Virtually every card has been modified in some way, leaving me with the conviction that they saw extensive use, somehow. Also, the diodes are D660 diodes, if that matters. Some are of the older, black kind, and some are the newer clear glass kind, (both with resistor-like markings, blue, blue, brown). There are lot codes on the TTL, but I don't know how to turn those into dates. The numbers are like "6903", "6908", "6910", so maybe I am looking at chips manufactured during 1969, which would place the boards manufactured around early 1970? I don't know what to make of the TI chips with "6915" on them if that were the case. Vince

From: "der Mouse" <mouse(a)rodents.montreal.qc.ca> Thanks! These boards appear to date from mid-year 1969, then. Vince

From: "Huw Davies" <huw.davies(a)kerberos.davies.net.au> I/O Very good. Unfortunately, that is exactly as much as we already knew. The question wasn't "what is it", but rather "what is it for"? If there were an entry under "Firmenportale" in this table you'd have nailed the answer :-). Though more detail about "what is it" would be nice, too, since I don't know what "Line I/O Control" means either. Google won't match anything with +pdp-8i +m750 when I try. Ah, I can find that page with "m750 pdp -inkjet". I had previously found http://pdp-8.org/mixed.txt and similar module lists. Thanks! BTW, anyone know what goes into a UDC-8? That appears to be a PDP-8 option that I can't find any detail about, and I'm wondering if it used the M750 :-). Vince

From: "Antonio Carlini" <arcarlini(a)iee.org> Whew. It took me a while to download that thing and verify what you said. So does that mean the M750 goes into the phototypesetter stuff, or was it something else that needed the Teletype Multiplexers? Vince