Re: Altair 8800 with Processor Technoloy MB-1 mother board
- Hi Jack,
If you are using an Altair CPU board along with your 8K memory board, and that is all you have in the system, then termination is not necessary at all. Termination is only helpful when you want to run faster - for example with a 4 MHz Z80 CPU board.
I haven't looked at the MB-1 in quite a few years. But as I remember, the original setup of the board worked just fine, though they did make a few revisions over time.
What is the nature of the failure? Have you looked at the bus signals with a scope?
Also, what are the resistor values on your board? - what is the pull-up value, and what is the pull-down value?
The most common values are 360 ohms and 390 ohms, with a reference of 2.6V.
If you send me your email address, I will send you the manual for the Godbout active terminator board. This manual has a pretty good explanation of the theory of active terminators for the S-100 bus.
--- In email@example.com, "pipercub" <pipercub@...> wrote:
> I have this computer with the CPU board and 8 K memory board that I am having trouble getting it to work properly. I don't have the original instruction manual, but I was able to download a instruction manual for the MB-1 mother board. The downloaded instruction manual shows different terminating resistors and it does not show a pot to adjust the voltage.If someone has experience with this board or a copy of the instruction manual with the pot to adjust the voltage, I would like to hear from you. I would like to know if my circuit is the latest circuit or if I need to upgrade the board per the instruction manual that I have.
> Thanks for your consideration.