8bit CPU project had problems - ***SOLVED***

[ebclr]

You already proved, you have a very big patient, making this forest of jumpers, that even work

Now go the next level of patient, and remake like this

[grumpydoc]

You already proved, you have a very big patient, making this forest of jumpers, that even work

Now go the nest level of patient , and remake like this

The back of that must be fun

[PauloConstantino]

Heres a video of my cpu working:

[MK14]

Nope.... changed the RAM to a 5V one, but the problem still occurs.... I am very mad now!

Since you discovered that you had inadvertently put in a lower (3.3V supply voltage) one, and it was NOT working properly above around 3V. Trying the proper 5V one, was a good thing to try. But was not necessarily going to fix all problems.

PROBLEM SOLVED !

The problem actually 2 bad connections. A very small jumper connection made with a resistor lead that was going to ground on one of the address pins of my microcode proms was not connected. It was offset from the correct pin. Another jumper got disconnected somehow, inside the jumper forest, so I never saw it. I saw it today after spending a lot of time looking around and testing IC pins with a logic probe.

The CPU is now running at light speed correctly without crashing. The moment I connected the bad connections it started working.


HUUURAAAAAYY !!!!


Like I said, I was skeptical the problem was inductive or capacitive coupling and so on.



I appreciate everyone's help a lot.



Stupid me. Apologize for kinda wasting your time on this. But it was very hopeless to be lost in the forest of illusion (super mario world pun intended).

Debugging/fixing things often needs lots of messing around, and trying/testing things, until you find the real problem(s).

As others (and I) have said. Better layouts and construction techniques, may have made the debugging easier.

The stray capacitance/inductance and cross-talk etc can be big headaches, especially at ever higher frequencies. So I think it was worth pointing out.

Anyway, congratulations on fixing it! 

[MK14]

Heres a video of my cpu working:

Thanks!

I've enjoyed watching the video. It was very nice seeing that program run, and a brand new and freshly designed cpu, making the light of day.

I'm amazed at how quickly you have designed and built it. I assumed/thought that it had been built up over a period of months, rather than a week.

If I can be JOKINGLY slightly rude about a tiny part of the video. I love the bit where you have the camera over it and it shows a massive mass of wires of incredible size and complexity, when you say something like "It is only a SIMPLE cpu/computer". N.B. This is NOT a criticism, just poking a tiny bit of fun, at it. You have done EXTREMELY WELL!

In fairness, you are RIGHT. It is only a simple cpu, especially compared to the massive (number of transistors) modern cpus, such as the Intels latest ones. But all those wires makes it look like something big and highly complicated.

I can see that you have had a lot of fun, designing and building the cpu. So good luck!

[ebclr]

Would be nice to have parts list

[PauloConstantino]

Would be nice to have parts list

Schematics available

[Audioguru]

That is the messiest circuit I have ever seen BY FAR! Of course it has problems.

I made some very complicated high speed digital circuits soldered on stripboard. The layout was planned then the strips were all cut to be as short as possible and formed half of a pcb wiring. The parts and a few short jumper wires formed the other half. The compact circuits worked perfectly and looked good enough to be sold as the finished product.

[PauloConstantino]

That is the messiest circuit I have ever seen BY FAR! Of course it has problems.

I made some very complicated high speed digital circuits soldered on stripboard. The layout was planned then the strips were all cut to be as short as possible and formed half of a pcb wiring. The parts and a few short jumper wires formed the other half. The compact circuits worked perfectly and looked good enough to be sold as the finished product.

If you have read my last posts the problem has been **SOLVED**. Duh.

[PauloConstantino]

You already proved, you have a very big patient, making this forest of jumpers, that even work

Now go the next level of patient, and remake like this

This is what I plan to do:

[MK14]

Wire wrapping can take quite a long time. I'd suggest you seriously consider PCB.
The costs of getting the boards made externally have generally come down a lot, over the years (and decades), since the 1970's.
There are many options for automated PCB design software (from free to hobbyist affordable to expensive).

You could use a number of standardized size PCBs, and some sort of back-plane or something to connect it all together.
One big PCB is also possible.

If the chips were all socketed, you could even go through different stages of design level. If you had any rarer TTL type devices. With no extra cost for the TTL (e.g. 74HC) chips. Although the same would be true for wire wrapping, except it can take ages to make a new generation of wire-wrapped boards.

[PauloConstantino]

Wire wrapping can take quite a long time. I'd suggest you seriously consider PCB.
The costs of getting the boards made externally have generally come down a lot, over the years (and decades), since the 1970's.
There are many options for automated PCB design software (from free to hobbyist affordable to expensive).

You could use a number of standardized size PCBs, and some sort of back-plane or something to connect it all together.
One big PCB is also possible.

If the chips were all socketed, you could even go through different stages of design level. If you had any rarer TTL type devices. With no extra cost for the TTL (e.g. 74HC) chips. Although the same would be true for wire wrapping, except it can take ages to make a new generation of wire-wrapped boards.

The magic of it is building it manually. I advise you to consider wirewrap when designing yours. ohhhh boy its all so easy

[BrianHG]

This is what I plan to do:

Wire wrapping can take quite a long time. I'd suggest you seriously consider PCB.

When I did some work for a company called RCS Management back a good 20 years ago, they made a 68040 accelerator CPU card for Amiga 2000s, with 32mb 32 bit ram modules.  They showed me their prototype and it was a functional 25Mhz wire-wrap board.  The ram was running at 50Mhz.  Wire-wrap works...
Attached is the production version of the Fusionforty accelerator board...

[PauloConstantino]

This is what I plan to do:

Wire wrapping can take quite a long time. I'd suggest you seriously consider PCB.

When I did some work for a company called RCS Management back a good 20 years ago, they made a 68040 accelerator CPU care for Amiga 2000s, with 32mb 32 bit ram modules.  They showed me their prototype and it was a functional 25Mhz wire-wrap board.  Wire-wrap works...
Attached is the production version of the Fusionforty accelerator board...

That's really awesome! Yes wirewrap rules!