One more try - Can you ID this S-100 Serial board?

Thu Oct 1 18:27:29 CDT 2015

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
>
> That's an intriguing and very real possibility, but then there's this:
> http://www.mct.net/ - Does that logo look familiar? Founded in the 80s,
> controller boards, interface modules, single-board computers.. but yes,
> they are in Germany. I did try contacting them, but never heard back.
>
> @All
>
> To answer a few questions:
>
> Yes, I am certain this is an S-100 board. It was pulled from the Altair I
> rebuilt and the PO confirmed that he "had a terminal or something"
> connected to it.
>
> The burned area on the board is where a couple of zener regulators gave it
> up. You can maybe see that I've replaced them with 3W zeners and 1W
> resistors. I believe these create +/- 12V supplies for the op-amps and
> RS-232 levels?
>
> I did some tracing on it, not my cup of tea, but I did learn some things..
> here's what I found: Each of the two 10-pin headers (I'll call these serial
> ports) seem to be wired the same, with duplicate component setups for each
> port.
>
> Pins 4 & 6 connect via 175R and 47R resistors, respectively, to one input
> of an XNOR gate on an LS266 chip. Second input to same XNOR gate seems tied
> to Vcc via jumpers. Output of XNOR gate has 1K pull-up to Vcc (open
> collector output) and then connects to pin 20 on the 1014/15 UART which is
> "SI". So pins 4 & 6 seem to be our serial inputs (RxD) with two different
> series resistances offered (175R or 47R). Might be an input voltage divider
> or termination option?
>
> Pin 1 connects to the collector of a 2N3906 which is in turn driven by the
> output of one section of an LM1458 op-amp. The non-inverting input of the
> op-amp connects back to pin 25 on the UART, which is "SO". I'm not sure
> what the inverting input of the op-amp is tied to.. perhaps it's part of an
> enable circuit? But it seems pin 1 is our serial output (TxD).
>
> The other port pins are variously tied to resistors, jumpers and/or 74XX
> logic. These might be our handshaking lines, ring detect, etc.
>
> That's all I know so far.
>
> On Thu, Oct 1, 2015 at 3:30 PM, Chris Elmquist <chrise at pobox.com> wrote:
>
>> 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:
>> > I had a look, and it seems to me that there is more going on on this
>> > board than just serial ports.  It is even possible that the system it
>> > was in had essentially re-purposed the board to use for a serial ports
>> > in a way that the original designer did not intend.  That would explain
>> > the lack of obvious level shifting - it may have been used for TTL level
>> > serial I/O.
>> >
>> > Also, there are lots more passive components on this board than I would
>> > expect for a serial interface board.
>> >
>> > A company with these initials made EPROM programmers, though their logo
>> > was different - but perhaps it changed over time.  Maybe this was a very
>> > early interface board to one of their very early programmers - and
>> > perhaps it is missing some of the parts, like connector headers and
>> > resistor packs, and then was re-purposed.
>> >
>> > JRJ
>> >
>> > On 9/30/2015 7:52 PM, drlegendre . wrote:
>> > > (Months along, posts to several boards / lists, still no help on this
>> one..
>> > > so I'm giving it another shot. I'd really like to use this board)
>> > >
>> > > Been trying to no avail to find any info on this 'MCT' S-100 serial
>> card.
>> > > I'm pretty sure the card works, as it came from a previously-working
>> system
>> > > - but all documents are missing, and without the info, I have no idea
>> how
>> > > to put it to use. Photos are here:
>> > >
>> > > https://nerp.net/~legendre/altair/mct_serial_01.jpg
>> > > https://nerp.net/~legendre/altair/mct_serial_02.jpg
>> > >
>> > > Other than what I believe is an artwork / batch number on the rear,
>> the
>> > > only marking is "Assy 105510" on the front silk screen. My hunch is
>> that
>> > > this may have been a fairly generic 'OEM' type card which could have
>> been
>> > > re-badged and sold under one or more different names. So perhaps the
>> docs
>> > > exist under a name other than MCT?
>> > >
>> > > Any help greatly appreciated - thanks!
>> > >
>> > > -Bill
>> > >
>>
>> --
>> Chris Elmquist
>>
>>
>