Simple questions on the replica kit

[herby1620]

Sounds interesting, the expansion board and the other stuff. I assume that if one is so inclined, they could (after verifying that it works correctly) use a more modern EPROM (like a 2716) with a bit of "blue wires" added. That would be twice the 4x1702's. Besides easier to get and modify.

Do you have any pointers to the memory layout of the Altair 680?

Somewhere I saw a listing of the internal (EPROM) code. Pointers to that either?

All of this is getting me interested.

[Grant Stockly]

You could replace the 4 1702A EPROMs if you wanted to, but what would be the fun in that!

I tried to keep part selection identical to the vintage one in all areas except the power supply.

I have all of the EPROM code and can post it later.

[herby1620]

While I agree that the 1702's were in the original, one must consider one thing: They were obsolete when the thing was designed. No fault of yours, only the Altair people.

My original design of my 6800 CPU board (back in 1975) used a 512x8 EPROM (a National Semi 5204 as I remember it) which was more reasonable then. It needed a -12 supply as well, but worked quite well. The next year Intel released the +5 only (on read) 2716 which was real nice. I used it in a later revision of the CPU board so I could include bootstrap programs.

One thing I was able to do was build a 2k-2k board that has a single 2716 and 2k (16 chips) of 2102's. The 2716 part even included the timing to make a programmer (you needed to add the Vpp supply). In that I was able to get Tiny Basic in the rom, and use the ram work working storage.

Those were the days......