Cumulus Issues

[Godzil]

But at least making a Cumulusbusbus should be fairly simple to make with R or C on all the lines to prevent the ripple effect.

i can try that.

On which line is on the original Microdisk the edititable resistor and what is the value of it?

There is no way to put a VR the same way as the Microdisc, as it is used in the 74221 circuitry to generated derived clock from Phi2 (see the bottom of this image.) All of this part is entirely generated inside the CPLD..

What I think could be fairly easy to do is to make a small PCB that will be plug either on the cumulus side or the cumulubus side that will add R on each lines used by the cable (but it may need one on each side)

Orm if i'm correct, put a C on each line between the line and ground to force the signal to not rise too quickly of fall too quickly, but the value must be wisely choose to not make the signal too slow...

The first (and easiest choice) will be the R, one side should be OK

[metadata]

here is a data line... looks good to me. So what can we do with a resistor better?

[metadata]

here are two maybe interesting pictures from the d2 pin. Sometimes the high status is not 5V. Maybe this is a problem... don't know yet.

[metadata]

@peacer did you only change the ram in your oric? i looks like that the IC's IC20 and IC8 are also newer. Original are this chips 74LS257 but you have 74HCT257 which are newer and has different high and low level voltage.

[peacer]

Yes. Only rams are changed 10 yrs ago. No other modifications are done. We've bought Oric very lately in 1987 or 88 I guess. Maybe it's from later producted series.

[Godzil]

Metadata: There is a lot of noise, and the ripple effect is clearly visible on your screens.. And the voltage drop is not normal..

[Chema]

No, that voltage drop doesn't look good. Is that a data line written by the cumulus as seen in the Oric bus or written by the Oric as seen inside cumulus... ? Maybe there is something there that could give us a hint...

[Godzil]

And the second screen is really noisy..

Can you try just for the test to put a 50ohm resistor in line on D2 and do the measurement again?

[metadata]

Can you try just for the test to put a 50ohm resistor in line on D2 and do the measurement again?

this doesn't work. The Oric then boot no more and the signal is worse.

[jorodr]

I have the same problem as Peacer. My Cumulus work perfect with one of my Oric Atmos and don't work at all on my Oric Nova 64. Both computers work with no problems with my microdisc clones, but with Cumulus Nova shows strange symbols exactly as peacer's video. Sorry, I am reading this discussion for a first time. I have 6-7 atmoses and will try every one if it works. Will scope some signals on working and not working to see the difference. Just need some time...
That I can say is that I'm fighting with Oric bus for a years. Everyone knows that it's very complicated. The things are going much ugly with the differences of various chips, depending of the type, depending of the supplier and so on. Because the computer work perfect with Microdisc I thing the problem is in the buffers. It seems to have many timing differences between the chips. The original Microdisc work with 74LS244. My Microdisc clones are using almost the same schematics, but work perfect only with 74HCT244 buffers. My Dos 8D controllers works good with 74LS541 of some suppliers and don't work with other. Maybe if Metadata try to change the buffer chips will have different results... Separately it's strange to buffer only the address bus and not the data bus... Anyway I hope to find the problem. Is there any other schematics of Cumulus to try to change it, not to use just gerbers? I have found only that:
http://retromaster.wordpress.com/cumulus/
but it's not full schematics. I thing if try to remove the buffer board and use only high quality ribbon cable the things will going better. I have build a lot of controllers that are using buffers on their side, not on expansion port side and they all work good.

[kenneth]

It could be interesting to disconnect the 5v link between Oric and Cumulus and connect the 5v of Cumulus Interface with a 5v external power, that could relieve the computer.

[peacer]

Thanks Jorodr, I feel better now to see someone with the same problem

Common problem means common solution. I hope we'll find a way to solve this and let cumulus work with every Oric computers properly.

As I said earlier, I've contacted retromaster who is also from my country and explained the situation but as he is probably so busy as he claimed in his blog. he still didn't replied by now. When he does, I'll let you know about his opinion and possible suggestions too.

Problem seems to be very simple to be solved, but for now we can not find the answer. Cumulus works perfect. Oric works perfect. But they can't get along with each other properly. I still think It should be so simple to solve..

I hope I'm right about this prediction.

[Godzil]

buffering the D bus is not that hard, but it's not sure that it will really
help

[metadata]

I have the same problem as Peacer. My Cumulus work perfect with one of my Oric Atmos and don't work at all on my Oric Nova 64

can you make a picture of the pcb and upload it here?

[jorodr]

I will picture the PCB today and will upload, no problem. Do you want to make video?