On Sun, Oct 4, 2020 at 11:42 AM Josh Dersch <dersc...@gmail.com> wrote:
> On Sun, Oct 4, 2020 at 10:26 AM Brent Hilpert via cctalk < > cctalk@classiccmp.org> wrote: > >> On 2020-Oct-04, at 1:22 AM, Josh Dersch via cctalk wrote: >> >> > More mysteries while poking at the MDP-1000. Spent some time this >> evening >> > working out the rest of the signals on the power harness (I suspect >> inputs >> > for an LTC circuit and a "power good" signal, as well as something >> > connected to a relay on the backplane, probably related to power >> control). >> > >> > There are a lot of unidentifiable ICs on the main CPU logic board and on >> > the backplane, mixed in with bog-standard 7400-series TTL. Curious if >> > anyone has any ideas, as my searches and perusal of >> datasheets/databooks on >> > Bitsavers have turned up nothing. These are all TI-manufactured ICs, >> 1969 >> > manufacturing dates, with "SN48xx" and "SN63xx" part numbers (a few omit >> > the "SN" prefix.) I'm wondering if these are just standard 7400 ICs >> with >> > special codes; for example there are several SN4816's near the edge >> > connector for the I/O bus, where a 7416 might (?) make sense, and from >> some >> > basic probing and following traces I think the pinouts make sense. >> > (Everything's conformal coated so it's a real bear to beep things >> out...) >> > >> > Any ideas? >> >> I have run across TI ICs from that era with odd/unknown series numbering, >> in particular the SN3900 and SN4500 DTL ICs. >> Notably: >> - by pinout they match up with standard DTL series ICs, >> - I have only found these in equipment from one manufacturer: >> calculators built by Canon. >> >> I received a solitary page of datasheet for some of them (by way of a >> Canon service center many years ago), but I have never seen them mentioned >> in TI databooks from the era, even in those sections where they list e.g. >> "other products from TI" and proceed to list little known series and part >> numbers. >> >> So an obvious guess is these were house numbering systems of standard >> parts done for the purchaser/equipment manufacturer but with TI's format >> scheme rather than a format specified by the manufacturer. Another guess >> would be standard parts tested and selected for purchaser-specified >> parameters, although that seems a little excessive for these cases. >> > > Yeah, either of those options seems a likely possibility. It definitely > seems like they were building this thing for bulletproof operation, so > maybe it really is the latter. > > >> >> The 54/7400 series originated with TI in 65, I'm not aware of them >> producing any other TTL series, other than perhaps second-sourcing some >> other manufacturer's. >> I guess that's another possibility - another manuf's TTL series, labeled >> differently. >> >> Odd that this Motorola CPU is filled with ICs manufactured by TI. >> > > Yeah, the irony of this was not lost on me. Other than the aforementioned > linear ICs in the core modules, every IC in this has a TI logo on it. > > >> >> It's conceivable, although it seems less probable, that they're DTL >> rather than TTL. >> >> On the whole, best guess would seem to be 7400-series inside. >> > > Yeah, I'm guessing (hoping) 7400 as well, especially since there are > actual 74xx-labeled ICs in here casually mixed with the 48xx and 63xx. > > A thought occurred, that if I get desperate I could remove a few of the > ICs and attempt identification using the IC tester I have. Not going to do > that unless I can't figure it out any other way. The good news is there > aren't too many varieties. I haven't done a full inventory but there's not > more than a dozen or so different types in here. > > >> >> -- >> >> On another issue, did you trace the +/-15V lines to the core >> address/inhibit drivers? >> Could some of the remaining wires from the PS be other core supplies - >> 15V was a little low compared to most core systems I've seen. >> >> > I did manage to trace the +/-15V lines to the drivers on the core memory. > I don't believe any of the extra signals are other voltages -- three of > them go to the CPU board, one goes to the aforementioned mystery relay, one > goes to a tiny bit of logic on the mainboard (I suspect some manner of > LTC), and the last goes to a trace that just dead-ends and goes nowhere at > all. The very little documentation I have on the CPU itself suggests that > the supply provided only +5 and +/-15. There are two sets of power rails > for each; the first goes to the CPU, front panel, and two memory slots, the > second set goes to the other two memory slots. I suspect that upgrading > past 8K of memory required a power supply upgrade. > > - Josh > > > Just made a minor breakthrough; a random usenet post suggested that the MDP-1000 was just a rebadged General Automation SPC-12, and so it is. I suspect the internals of the unit I have (which is badged as an "MDP-6650" on the rear) are a bit different than either the MDP-1000 or the SPC-12 (and I'm no closer to finding answers to my IC identification questions), but it at least gives me another avenue to explore... (Bitsavers has a few items: http://bitsavers.org/pdf/generalAutomation/spc12/) - Josh
