Simple questions on the replica kit

[herby1620]

From the pictures I see, it looks like some stuff was added to the back panel of the MITS 680. In another picture it appears that these are not connected. Is something planned?

Inquiring minds, etc...


On another front, is it possible to order the kit WITHOUT the transformers (switching supplies). My idea is to use "proper" supplies (+12, +5, -12) and bypass the regulators. Not exactly a true replica, but I suspect a "cooler" idea. I can get small supplies pretty cheaply at the local surplus store.

I was also wondering how the kit (original/replica) is expanded (or is it at all?)? The limitd amount of memory is a litle difficult. My 6800 box (I built it myself, etc...) has 60k of memory. It works quite nicely (lots of 2147's spread out over memory cards).

I guess I just like the front panel. I don't have one on my box.

[Grant Stockly]

From the pictures I see, it looks like some stuff was added to the back panel of the MITS 680. In another picture it appears that these are not connected. Is something planned?

DB9/DB15HD ports for serial/video.
DB25 x 2 for serial/parallel/etc
.25" holes x 2 for cassette tape play/rec
.25" holes x 3 for video/stereo audio
PS/2 x 1 for keyboard

I am working on a small ADM3A terminal emulator. This is based on a $99 FPGA development kit. It would work good to place the FPGA inside the 680 case and have a keyboard / VGA / NTSC connected directly to it. That would make a sleek system!

The stereo audio is there for a future development. They can be used for anything...

On another front, is it possible to order the kit WITHOUT the transformers (switching supplies). My idea is to use "proper" supplies (+12, +5, -12) and bypass the regulators. Not exactly a true replica, but I suspect a "cooler" idea. I can get small supplies pretty cheaply at the local surplus store.

Yes. I can sell it without the supplies. It would cut about $60-70 off of the price.

I was also wondering how the kit (original/replica) is expanded (or is it at all?)? The limitd amount of memory is a litle difficult. My 6800 box (I built it myself, etc...) has 60k of memory. It works quite nicely (lots of 2147's spread out over memory cards).

I have designed a little board with 32k of SRAM and 32k of bank swapped EEPROM. For the current price the kit comes with that upgrade for free. The EEPROM comes with 2 versions of basic and the assembler/editor.

Also included for no extra cost is VTL-2 on vintage 1702A EPROMs.

These bonus items add an extra $100 of value or so to the kit, and greatly expand what it can do.

I guess I just like the front panel. I don't have one on my box.

Front panels are pretty handy... Its easy to see if it has crashed.

I've loved lights all my life. I had my own collection of Christmas lights when I was 6-7. Before that my parents bought me a set of lights powered on a C cell battery.

[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......