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View Full Version : Altair 8800 using 8800b wire wrap CPU Board



Marty
June 19th, 2017, 08:34 AM
Hi All;

I have wire-wrapped an 8800b CPU Card, that IS running on my Altair 8800 Machine..

I have based this on the Pictures from Tom Sanderson's site of Tom Durston's Altair 8800 Machine and Much Help from Martin Eberhard, finding a Problem I had with my Board..

So, I am using a modified 8800b CPU card and an original 8800 Front Panel and Not an 8800b Front Panel..

This is just to let others know that it is possible to do this and have a running Machine..

I still have to see if it will run Altair Basic to complete it's final Test, before I can Say it is Totally Working..

THANK YOU Marty

glitch
June 19th, 2017, 10:16 AM
Good stuff, but I don't see why there would be doubt about it being possible -- there are non-Altair CPU boards that work with the Altair front panel. The TDL ZPU was one such board, Josh Bensadon's 8080 CPU board is another. I've also seen an Ithaca Z80 board wired in with an adapter board.

Marty
June 19th, 2017, 11:38 AM
Hi All;

Glitch, Thank You for Your Input..

Yes, I know that there are other Boards, I have a few, that can Run of a Plain Altair..

But, this is slightly different, One is that it is Wire-wrapped, and I was Told that it may not run a full Frequency, because of it being wire-wrapped..
And Second, that a Standard 8800b CPU card will run only in an 8800b or 8800bt or similar type of Altair systems.
Because some of the needed signals that were on the 8800 CPU card and possibly others as well, were put on the 8800b Front Panel and Front Panel Card..
And, so an 8800 CPU Card will not work in an 8800b and an 8800b will not work in an 8800..
There are three IC's needed to make an 8800b work in the older System..
I do not know the Design History behind the 8800b and whether the CPU card was first or not, But, based on the Information that I have the modified 8800b was created first and that was used to test the various circuits needed to make the full 8800b..

Anyway, the Reason, I went this route, is I needed a more Stable Clock signal for trying to get my Meca Alpha 1 Cassette Controller working again, and the clock signal in the 8800 was not stable enough to make the Phase Lock Loop Lock into the signal from the tape..

THANK YOU Marty

Chuck(G)
June 19th, 2017, 11:43 AM
Who told you that it wouldn't run at full frequency? Heck, I've got WW boards with ECL on them running at 40MHz. I routinely make WW prototypes of stuff running at 168MHz. Having good power and ground planes helps a lot.

It was common practice to WW up prototypes of things like the IBM 5150.

WW has certain advantages over PCB--it can be easily modified. You can be very precise on conductor lengths without worrying about routing issues. Crosstalk issues can be minimized (that ECL board that I spoke of uses twisted-pair (differential) lines). Assuming careful work, using the right tools, there's no reason why a WW board shouldn't last 40-50 years or more.

glitch
June 19th, 2017, 11:44 AM
You don't have to worry much about speed with wire wrap on the S-100 bus -- properly done, it's usable to 20 MHz. As long as the board design is sane it'll be fine!

Interesting on the issue with the clock -- I assume this is because the original 8800 CPU board didn't use an Intel 8224 clock generator, and the 8800B CPU board does?

Marty
June 19th, 2017, 01:59 PM
Hi All;

Chuck and Glitch, Thank You for setting me straight on the Wire-wrap Issue..

"" Interesting on the issue with the clock -- I assume this is because the original 8800 CPU board didn't use an Intel 8224 clock generator, and the 8800B CPU board does? ""

Basically, Yes, the original had 74123's for the clock spacing and width, and the 8224 is a divide down from a higher Frequency..

I first would like to be able to Read / transcribe the Information from the Cassette tapes that I have and see What was used as a basis for their Operating System/Assembler, Etc., At least that is my goal..

I bought the Cassette System New in about 1977, and at that time I had an Altair 8800b, and I have never had the Cassette System working..
When it was new, from (I Think) bad Memory and lately from Outside Interference like Cell phones/Internet and such the wrack Havoc with the Low Level Signals coming from the Heads on the Tape Decks to the Pre-Amps..
Once I know or can figure out What Frequencies it uses to write to the Tapes, I hope I can make tighter Op-Amp Circuitry to only amplify the correct Signals..

THANK YOU Marty

glitch
June 19th, 2017, 04:31 PM
As with the DG cassettes, I'd record them to the computer before you do much with them -- who knows which read will be the last read!

Marty
June 19th, 2017, 06:12 PM
Hi All;

Glitch, I wish it was that Easy, as putting the Cassette into a regular Cassette Tape Player and copying the tones to my Computer..

I used to have an Audio to Computer Program, but I forget what it is called, but there is more to it than that..

It uses a Triple I Cassette Phi Deck at a greater speed than a regular Cassette, so I have to use that Deck, then the signal from the Heads would need to be amplified up to Audio Input Level, and then maybe the capture program would/could capture it and the signals possibly sorted out..

I would be Glad for Any Help that You or anyone could provide.. I just want You to understand that it is not a simple matter of popping it into a regular Cassette Player and out would come the correct tones..

I thought I had sent a copy to John Monahan's S-100 site, but the Board is not there, so I must be mistaken about that..

THANK YOU Marty