JezC H5 C5B Build - one STep beyond...?

[exxos]

I still find it odd that I have the 3 H5C boards all showing a very similar problem...only the number of bombs shown when it crashes on a floppy access seems different across all 3 of them.

Yep. Like I said before, you will have to send me one to debug because I have never had that issue on any builds and not aware of anyone else either having the same issues.

[JezC]

I still find it odd that I have the 3 H5C boards all showing a very similar problem...only the number of bombs shown when it crashes on a floppy access seems different across all 3 of them.

Yep. Like I said before, you will have to send me one to debug because I have never had that issue on any builds and not aware of anyone else either having the same issues.

Yes. though I'm aware of how little time you get so I'd prefer to let you be creative rather than debug my sulky H5C boards...

I do appreciate the offer though! (I realised the above could seem a bit ungrateful - that's not my intention!)

[exxos]

Yes. though I'm aware of how little time you get so I'd prefer to let you be creative rather than debug my sulky H5C boards...

I do appreciate the offer though! (I realised the above could seem a bit ungrateful - that's not my intention!)

Yes I understand :) But like you say, 3 boards having the same issue.. It really needs to be diagnosed in case there is something "wrong" with the H5 design somewhere.

I'm not sure really what else to suggest unless your ROM IC is bad somehow ?

Are you using a MPF920 drive ? I don't know if anyone has tried a original drive yet. Gotek works if the jumpers are set correctly.. I don't have one.. Only use MPF920 here..

But even so, with TOS104 , I think with the drive unplugged you can get to desktop still ? If you can get to desktop, and have my diagnostic cart, you can configure that to run GB6 from cartridge drive at least.

[JezC]

Yes. though I'm aware of how little time you get so I'd prefer to let you be creative rather than debug my sulky H5C boards...

I do appreciate the offer though! (I realised the above could seem a bit ungrateful - that's not my intention!)

Yes I understand :) But like you say, 3 boards having the same issue.. It really needs to be diagnosed in case there is something "wrong" with the H5 design somewhere.

I'm not sure really what else to suggest unless your ROM IC is bad somehow ?

Are you using a MPF920 drive ? I don't know if anyone has tried a original drive yet. Gotek works if the jumpers are set correctly.. I don't have one.. Only use MPF920 here..

But even so, with TOS104 , I think with the drive unplugged you can get to desktop still ? If you can get to desktop, and have my diagnostic cart, you can configure that to run GB6 from cartridge drive at least.

The possible issue with the H5 probably depends on the number of H5 boards out there working with floppy drives or replacements (e.g. Gotek) compared to the 3 I have but I understand your concern.

I do have some Goteks as well as at least one MFP920 which I will try later to see.

As long as there is no floppy disc in the drive I get to the desktop just fine - I'll have to solder in the cart connector before I can run the diag cart (but I have done that successfully on one of the H5C1 boards with a similar floppy issue & everything else seemed OK).

Certainly a weird one...I'll try to get some more time on it later today...

[exxos]

My only thought / concern is I added a multiplexer between the DMA port and 1772. Atari had that as a clocked delay which never made sence. But maybe there was a another DMA bug which didn't show up on original STs as they didn't have the buffers until the STE came along which Atari kept the data latched for longer. Whereas on the H4 boards onwards the buffers are there but not clocked delays so data would be isolated faster.

But if that was the case, why would it only show that fault on your boards... Unless your using the same DMA & 1772 chip as which just happens to be "bad" ...

You said your H4 works but did it have the little DMA fix board? I'd assume so else I think the floppy drive wouldn't work without it.. A image of your working H4 may help..


EDIT:

Not simple.. but you would have to lift the 2 highlighted legs on the ICs... (EDIT: Cutting the track for IC4 likely be easier than lifting the leg)

Then connect the leg to 0v on IC4.

f.PNG

Connect the leg to 5V on IC5 (EDIT: You could cut that small track as lifting the legs likely be hard)

d.PNG

Or do some track cutting.. not easy either way unfortunately.

You won't get DMA port working, but it will enable the multiplex buffers all the time to see if that's the issue or not.

If that is the issue then every remake board prettymuch would have this problem :roll: That little inverter IC10 would need a small patch board to add a clocked delay to keep the buffers enabled longer basically the 1772 keeps data on its bus for ages after CS goes high. So the data latch time would be increased a lot.

[JezC]

Hi @exxos - I've seen this but not had chance to digest or act on it yet.

I can't find my MPF920 drive(s) at the moment but I do have a few Gotek drives I can try tonight.

My H4 does NOT have the DMA fix board fitted - I've been putting that off until one of the other boards is working...just in case I break the last one! :roll:

Floppy drive works fine without it (but not ACSI) - and I have used external floppy B as well as A (at different times) with no issues on either - so far!
I did have issues with it - but that was with TF536/ST536 fitted (floppy worked to boot into EmuTOS but then was not working until a reboot and then not with EmuTOS running but I just put that aside until it was sorted & not had time to revisit it since then)

I'm sure that given the number of H5 boards sold others would have seen and reported the problem if it were as bad as the STE DMA issues.

I'll look at the DMA chips and FDC varieties but I'm pretty sure I have DMAs both IMP and non-IMP bought and recovered from working systems & WDC 1772s, VLSI 1772s and even a couple of AJAX chips.
I'll collate the list to see what is where in case that gives another clue.

I'll get a photo of the H4 later too.

I do still have the H4 and H5B1 bare boards on the backlog but I was 'saving' those until I had at least a few of the others working and then decide what spec I wanted those to be...

Sadly, still reliant on the money from my day job so i have to get back to that until this evening...

[exxos]

@JezC That's the odd thing though, must be like 100 boards out there now.. It could just be a fluke all your chips just happen to show the fault.

I do sometimes have issues where I've been assuming it's 30 year old floppies which randomly thow out read errors... But maybe that's not actually the case, and I'm seeing the same issue as you, just not as pronounced...

[PhilC]

It sounds too much of a coincidence that it's all three of the boards @JezC.All of mine have worked fine and the one I fixed for someone else was a PCB track issue.

[exxos]

It sounds too much of a coincidence that it's all three of the boards @JezC.All of mine have worked fine and the one I fixed for someone else was a PCB track issue.

Yeah it seems odd it's only @JezC boards.. But he's got 3 different revisions now.. If his H4 works... Coincidentally not got the DMA mod that all the H5s have...

If he tries my idea out then we will know for sure.. It would also explain the 7474 on the STE diagram..

[JezC]

Well, I will see what I can get done tonight and then see if it's best to send at least one problematic H5C to @PhilC or @exxos to rule out any potential wider issue.

Thanks again