I couldn't spot how they did level shifting to RS232 levels. The SI signal appears to go to a 7400 next to one of the Uarts. One of the Uarts is one which requires it would seem 12 v as well, but it doesn't do the levels for rs232 (AY-3-1015) I'd need sharper images and possession of the board to peer at it for an hour or so to try to figure it out. Also the edge card space from the dual 50 pin headers seem to be suspicious. i don't have an S100 spec to look at handy, but I was going to see if there is any decoding going on, or maybe this is just a buffer board to go to another system. There seems to be a lot of LS244 and so forth going on on the way to the edge card connectors, which smells more like a buffer board than a serial board. that is is not populated but for the two 10 pin connectors is more interesting. Maybe someone else will figure out more or know more. thanks Jim On 9/30/2015 6:22 PM, drlegendre . wrote:

There are a couple of 8 pin ICs near the 10 pin headers, they look to be 1458 dual op-amps (I can't exactly make out the numbers...). Op-amps were often used as RS232 drivers. Give them +/-12V supplies, feed a TTL signal into one of the inputs, connect the other input to a voltage between the TTL levels (potential divider from the 5V line) and apply no negative feedback. The Op-amp output will swing between the supply rails. -tony

On 9/30/2015 10:46 PM, drlegendre . wrote: no disputing that. Glad Tony made his point, I was curious if it was early enough to not have had what we are accustomed to now days. Previous owner had it in an S100 system? that is my remaining concern. I have some pretty convincing boards which look like but aren't ducks. Interesting card, thanks for posting it. It'll be interesting to see what you find. I'm also interested in what the referenced info source, thanks Jim

I have been doing a bit of spadework on this one. There was a company call MCT who advertised in the PC Mag. in the early 80's The products were add-ons for PC's. The possibiliy that they made S100 products prior to 1980 is not an unreasonable one. So anybody with an early 80's PC Mag might find them. In fact any publication from about then may have a reference. Rod On 01/10/2015 13:30, tony duell wrote: -- Wanted : KDJ11-E M8981 KK8-E M8300 KK8-E M8310 KK8-E M8320 KK8-E M8330

On Thu, 1 Oct 2015, chocolatejollis38 at gmail.com wrote: Possibly, I mentioned this in the other thread. JDR Microdevices started selling stuff in 1979 and this board looks like it was made in 1980. I think this board might eventually turn up in an old magazine article or ad (Radio Electronics, Popular Electronics, Kilobaud Microcomputing, etc) since it looks like it may have been a kit.

I've got another theory regarding drlegendre's board. I happen to know via out-of-band information that he is here in MN. There is a company in the Twin Cities called Micro Component Technology that existed in the 70s, 80s, 90s and still today. They make handling and test systems for IC fabrication. http://www.mct.com/Company.aspx I'm willing to bet dollars to donuts or lingonberries to lefse that his board is a custom job made by the MN MCT and it went into the computer control of one of their machines from the early 80s. Something probably designed in the mid to late 70s. The logo on the board matches what I remember seeing on their building in Shoreview ages ago. I don't think it's the MCT that made PC (as in IBM PC) plugins... Chris On Thursday (10/01/2015 at 10:14AM -0500), Jay Jaeger wrote: -- Chris Elmquist

Now a question.. Can someone give me a quick rundown on how the CPU communicates with this board? Does the board show up as a few bytes in the memory map, like on page zero? Does it connect directly to some registers in the CPU? How does data move from the CPU / buss into & out of the board? In short, how does the computer know where to "find" the board - and how do they converse? I'm only concerend with the serial portion, the rest is still a mystery - the 50 pin headers might be anything from parallel ports to (proprietary?) controller interfaces. On Thu, Oct 1, 2015 at 6:21 PM, drlegendre . <drlegendre at gmail.com> wrote:

@Chris / All Unfortunately, I've never eyeballed the logo of the locally-based MCT corp so I can't comment on it, but again, it's an intriguing thought. And yes, it's quite possible that the PO knew or ever purchased this Altair from an employee there. He (PO) indicated that he bought the system second-hand, in the early 1980s, from an engineering colleague who worked elsewhere in the locality. And the PO is the kind of guy who would have hacked-out the cheapest and most expedient solution to whatever was presented. Don't get me wrong, the guy is quite sharp and well-educated, but just a real practical 'bailing wire and duct tape' kinda guy.. half EE, half farmer or something. ;-) Oh - about it being a 'kit'.. I gave a good look, and it's hard to say for sure, but the board +is+ totally hand-soldered. But the work is excellent. So it's either a well-built kit or a smaller-run factory board - but it wasn't wave / batch soldered. Also, I'm curious about the 50-pin headers.. why were they never installed? All of the other work was done, all the expensive parts (chips) are in-place - so why not a couple of cheap headers? Yes, a few resistor SIPs are gone, as is one chip missing, but still, you get the point. On Thu, Oct 1, 2015 at 6:56 PM, Chris Elmquist <chrise at pobox.com> wrote:

Here's more grist for the mill. I did contact and receive a reply from gentleman Herb Johnson at retrocomputing. I hope he doesn't mind if I quote his comments here.. they seem quite pertinent and they reflect or complement many of our working assumptions. Herb Sez: "Warning: I'm offering advice, which I do not warrant in any way. I am not responsible for loss, injury or damage to you or your equipment or software. Use any information, advice or suggestions I make, entirely at your own risk. Always work with caution. 1) identify big chips. AY-3-1015 is a UART, so is AY-3-1014. The crystal is probably a baud rate generator. Those two small connectors near the UART are probably serial ports. If you trace the lines and chips near those connectors, you can decide what some of the lines are. the UARTs have transmit and recieve pins so you can trace through from there. My guess is that the serial connectors are NOT "RS-232" because of all the resistors and caps. 2) identify connectors. There's two 50-pin connectors but they are not "populated". I see 74LS373 and '374 chips, those are 8-bit I/O devices. You can trace those, probably, to those connectors. This suggests the connectors are "parallel ports". 3) look at the S-100 connector. there's not that many S-100 pins wired to the board. That suggests it's an I/O board, which often only uses the lower 8-bits of address (and of course both 8-bit data line sets). 4) follow the traces. So it's likely this is a serial/parallel I/O card. If you follow a few address lines from the S-100, you'll find where they are decoded to specific I/O addresses, and see probably some jumpers to change that address. 5) tests. Before plugging the board into the bus, check the DC power lines for shorts. Check with an ohmmeter across all "tantalum" capacitors for shorts (under 100 ohms about) and replace those caps. When you apply power, confirm the regulator produces 5.0V. Be prepared to shut down your S-100 bus power at ANY sign of heat or smoke - and identify immediately any burned component. I often use a Variac to control power to a S-100 card or system. ---------- I recognize "MCT" as a brand of S-100 boards, but I've not owned docs for them, I don't believe. When you see MCT branded cards discussed, you might ask owners about documentation. I should create a list of undocumented S-100 cards, just for these kinds of boards. Let me know if any of the above information is helpful and any results from checking out your card as suggested. OK? Good hunting!" Thanks again, Herb - your time is sincerely appreciated! Nice to know a guy like that still has time for a newbish enterprise as this.. ;-) On Thu, Oct 1, 2015 at 8:26 PM, Chris Elmquist <chrise at pobox.com> wrote:

On 10/01/2015 04:36 PM, Chris Elmquist wrote: The problem is that there are and have been many, many "MCT" organizations. Just an image search for corporate logos for MCT shows a bewildering array to choose from. --Chuck

I think Holm nailed that one. The logo is probably just a coincidence, as it's pretty safe to say this board didn't originate in the 'Bad Old Days' of the DDR.. ;-) Seems like MCT in Shoreview, MN is our best working hypothesis. Would be nice to come across an advert or other piece of corporate ephemera from the early 1980s, to see what logo they used. On Fri, Oct 2, 2015 at 4:32 AM, Holm Tiffe <holm at freibergnet.de> wrote:

I'd say that nails it, good work! Presently, I have a mail in to a Ken Ramsey who is a VP of sales at MCT. He believes that they may well have made the board, and has promised to forward my photos to their engineers - now in Malaysia - to see if anyone recognizes it. But at least we know who made it.. this mystery may yet be solved. On Fri, Oct 2, 2015 at 1:52 PM, Chris Elmquist <chrise at pobox.com> wrote: