8080 FSGA model in an FPGA

I want to use the transistor board set as part of a possible computer kit / electronics trainer. I have just completed the Altair Kit reproduction that I've been working on for 9 months as a hobby. If I can stick with it and get that done on my time off, I think a transistor 8080 would be easy. ;)

Any way, I guess I would be happy if the transistor computer were instruction set compatible AND timing compatible. I really am not concerned about how the computer is constructed at the transistor level, but I want the status signals the same and the instruction set cycle count to be the same. If a program depends on a software delay loop, I would want it to be equal.

Maybe I'm trying to attempt too much. I think my best bet is to reasearch the 9080 emulator by AMD and duplicate that. Its possible I could rewrite the microcode to include status bit states. Who knows...

With this new information, does anyone see a different easier path? Or am I still just plain crazy? :) I won't be making any transistor

Grant

If you are just trying to build a trainer of some sort, wouldn't it be easier to build a simulation that could show all the internal states? It has got to be easier to do a simulation than a construction project from transistors or even from CPLDs.

I guess its because I'm in Alaska? The largest state in the union mentality causes me to want to build a computer from transistors? :)

I just find it so interesting that it can be done. Why not make a kit! :) Wouldn't a second box under the altair with a few hundred lights be neat to watch?

I really want to build a computer from relays, and even priced out some nice ones on e-bay, but I am concerned about how long it would last before failing...

Grant

If it is clocked with

One type of computer that might actually be interesting to build of relays and operate would be a time piece. To keep the power consumption down, you might use latching relays. The contain a permanet magnet that holds the contact in either state and a pulse from the coil is required to change the state. Each relay is then a FF. The logic would be done by stringing relays in series or parallel to form AND and OR functions (with or without inversions). You could also use diodes to form the logic if you want to save some space. There are some fairly minature relays available at around $5 or less. We are using some latching RF relays at that price. They are about 15 x 10 mm so a clock circuit might take up a square foot depending on the density. It would also tick every second with major noises on the minutes and hours.

I am working on a relay controller circuit for an RF module and when I do the test code, it will have a few options to sound out tap dancing like music. That should prove interesting and entertaining!

That is a pretty good idea. Would you have to use vaccume tubes with a crystal to generate the 1 second clock? (to maintain period technology)

Now you have my head spinning...Its a good thing I'm done with the Altair! :)

Before that I wanted to answer the question "What is the latency of a ping to a relay based computer?" My friends would hardly talk to me about that one. They think I'm crazy too.

ALL the relays need to be the clear ice cube kind with the LED to indicate state. Or a separate LED I guess. I really like visual things. :)

Years ago when I was in college, my dad got me a job with the railroad he worked for. I was an apprentice helper to the signalman who kept the signals working on the Old Main Line between Baltimore and points west of Brunswick, MD. One of the things that really impressed me was when I got to see inside one of the signal cabinets at a larger crossing. It had a dozen or so relays that were made of separate components. The top was a coil and the binding posts for the wiring. The bottom was a glass cover with the contacts inside. It was glass so that they could be visually inspected without disassembly. Inside each glass was a hand written tag showing when the relay was put in service and last maintained. This was in the 70's and the relays had been last maintained 20 years before and put into service 50 years before!

These things were about 8 inches square at the base and perhaps 10 inches to a foot tall. So they would be hard to make a clock from. But it was impressive to see something that was really made to last a long time in contrast to how things are made today... cheap to make and a low failure rate for 5 years maybe. After that it no longer matters since the device is likely to be obsolete. It makes me want to build things that last a long time.

Grant Stockly wrote: [snip]

A tuning fork might be more in keeping: middle A = 440Hz, which could make a useful timebase.

Hi Rick, Have you seen this?

Using surface mount and low current, the machine would be about the size of a refrigerator, and fairly slow, but workable. I doubt these small reed relays would even make a noise.

Its the "fortune" rule. Some> Grant Stockly wrote:

Why anyone would use those big relays and point to point wiring is beyond me.

What have we learned? There are pe>

This one is better than those:

He has it hooked to a typewriter for a terminal! In some of the sound clips you can hear it tapping out the answer! :) The thousand relays make some really neat sounds!

Grant

Pretty cool! If you read the updates on Harry Porter's machine he says he has Linux running on it!

scott moore wrote:

I don't think any software ever "runs" on a relay computer... ; )