exxos blog - random goings on

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exxos
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Re: exxos blog - random goings on

Post by exxos »

In light of the clock problems / DMA problems on the STE, I have currently decided to try clock sync approach. As I simply don't have time to do anything else for the foreseeable future.

The idea of this board is to just forget the system 8MHz clock and generate a new one from the master 32MHz clock. Then divide it down back to 8MHz. Of course it is going to have clock skew which will be near impossible to figure out without physically building and trying the thing out.

The overall idea is to have the 8MHz "CPU CLOCK" slightly advanced over the motherboard clock. As by the time it is propagated through the buffers and GAL , it is inherently being delayed by somewhere around 13ns anyway. So the clock advance has to be 13ns basically. Though this delay is compounded by the clock division logic on the board as well :roll:

Also further problems are because I simply don't know what the propagation delays are through the GST MCU. It is possible my new logic could end up being the same propagation delay going through the GST anyway. Though I doubt it would be that simple.

So I threw together this board which gives me some options experimenting with a new clock division circuit. If I can basically synchronise the motherboard clock with the CPU clock (after all the logic delays) then theoretically it would solve the DMA issues.

Ultimately I may have to have a chain of several buffers together fine tune delay. This could ultimately be needed because of tolerances on the GALs themselves. But as things are basically borderline as they are now I think if I can just advance by thing like 15ns, then it should be enough to solve the problem in the majority of cases anyway.

Likely some experimentation will be needed to see what the minimum and maximum delays are and try and aim for the middle ground timings.

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viewtopic.php?f=17&t=1585 Have you done the Mandatory Fixes ?
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JezC
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Re: exxos blog - random goings on

Post by JezC »

Just wondering if something like the old Cypress Roboclock might be an option for this investigation?

May not be 5v (can't remember but I thought we did have an equivalent 5v version) but I'm sure we used to use something like that to generate multiple clocks with different delays from a master clock (but this was back in the 90s)...
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Re: exxos blog - random goings on

Post by exxos »

JezC wrote: Thu Jun 08, 2023 9:59 pm Just wondering if something like the old Cypress Roboclock might be an option for this investigation?

May not be 5v (can't remember but I thought we did have an equivalent 5v version) but I'm sure we used to use something like that to generate multiple clocks with different delays from a master clock (but this was back in the 90s)...
Not sure I heard of that one.. There used to be a lot of really nice clock generator related chips years ago.

Part of the problem is down to I just don't have the capabilities inside a basic GAL to do much of anything, hence this "clock patch board". Again part of the reason why I redesign the booster to use the larger Atmel PLDs.

Though I don't really like the idea of just abandoning the current booster series because I think there is rather a lot of them out there now. Though when that design was done there was only really ultrasatan around and it had tested fine for years with that anyway.

Still rather frustrating as there is a weird unknown problem somewhere on the STE. I think at one point the blitter was malfunctioning but I cannot really remember offhand now. I'm just assuming currently that there is some sort of weird bus conflict possibly a issue with the interleaved RAM access or something. Cannot remember if the blitter suffered or not but I know turning the blitter off did not resolve the hard drive issues. In any case the idea is to simply shift the CPU timings back to what the stock system is and it should solve the problem anyway.
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viewtopic.php?f=17&t=1585 Have you done the Mandatory Fixes ?
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Re: exxos blog - random goings on

Post by exxos »

STE booster patch boards have been shipped :) Just a waiting game now :ball:

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Re: exxos blog - random goings on

Post by exxos »

Was just reading this thread viewtopic.php?p=78446#p78446 where I mentioned floppy issues depending on shifter versions..That's another dma oddity :roll:
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Re: exxos blog - random goings on

Post by exxos »

My clock sync boards arrived :) "sadly" I haven't got my STE on my bench due to working on the DFB1X stuff. But as soon as I get my falcon out of the way, I'll test the new clock board out.

I also have a few other ideas to try out for diagnosing the odd DMA issues..

I also need to revisit the problems with A1. viewtopic.php?p=20310#p20310
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Re: exxos blog - random goings on

Post by exxos »

Cool crash screen of the day!


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Re: exxos blog - random goings on

Post by Rustynutt »

exxos wrote: Fri Jun 30, 2023 11:00 pm Cool crash screen of the day!
Seen a LOT of bomb screens, never that many! You plug a MAC power cord into it?
:lol:
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Re: exxos blog - random goings on

Post by mrbombermillzy »

TOS error code for 20 bombs and lines: Bus on fire error.
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Re: exxos blog - random goings on

Post by Rustynutt »

mrbombermillzy wrote: Sun Jul 02, 2023 7:23 pm TOS error code for 20 bombs and lines: Bus on fire error.
:lol:
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