[Video] B-Roll: Investigating DSTB1 AltRAM issues on my STFM

[Badwolf]

Afternoon all.

I'm launching a new video series I'm titling 'B-Roll'.

Basically I don't have a lot of time of late so just in case you thought you'd got rid of me, I thought I'd put out some in-between content of what I'm working on where I can.

Effectively the sort of over-the-shoulder conversational style working vlogs larger channels might relegate to a 'second channel'.

Today I'm looking at my DSTB1.

I've been working on some firmware changes to try address an issue raised by @Oldskool on this forum and make the AltRAM more robust to DMA. I wasn't getting anywhere and realised that there was something else afoot.

Here's my (inconclusive) playing around with stock firmware and getting frustrating results.

Cheers,

BW

[Oldskool]

@Badwolf
Thanks for checking it. Cool.
I indeed tested hddriver, the one from the other guy Petari or something and emutos.
In Emutos I renember to have some similar issues but it’s some time ago. The first firmware was really unstable for me.
Can ship my dstb-1 to the UK…. Would that help?

[JezC]

Guess I'd better finish building my DSTB1 & program it up so that I can test it...(adds yet another task to the seemingly infinite list...)

No promises on timeline but there's a slim chance that I might manage it before @Badwolf builds another one from scratch... :roll:

[Badwolf]

There's a very nice comment on the video from the snappily named @user-ic6ei6yh9h who reports having five working DSTBs, so the chances are I've just buggered mine up and the original reported problem is indeed just the half-arsed DMA support.

But it'd be nice to be able to prove it. ;)

BW

[Oldskool]

Had a look at the comments and user @user-ic6ei6yh9h mentions he uses a lightning card.
So tried this as well.
@8 mhz no problems. @16 mhz ide is not recognised at all.
For the acsi port @8 mhz no problems. @16 mhz the issues as described earlier arise.
Very strange that @user-ic6ei6yh9 has no issues @ 16.

[Oldskool]

@Badwolf
Somehow I destroyed my Dstb-1. The main ic was killed and I measured a full short. How this happened I still don’t know.
After replacing all IC’s (just to be sure) it works again.
Now plugged into the ATX ST it works with IDE. And it runs DOTT without errors it seems…
Did not test it yet in the Phoenix…
So why it behaved so strange in the Phoenix? Maybe some incompatibility in the Phoenix maybe my Dstb-1 was always on the edge of death.
I use the second software release.
So maybe the issues I had reported were due to a bad IC or something or aliexpress junk or semi bad soldering…

Unleashing the full power of the 68000@16

IMG_2707.jpeg

Yeah a game with a main character which looks like me…he really does :(

IMG_2708.jpeg

[Badwolf]

@Badwolf
Somehow I destroyed my Dstb-1. The main ic was killed and I measured a full short. How this happened I still don’t know.
After replacing all IC’s (just to be sure) it works again.
Now plugged into the ATX ST it works with IDE. And it runs DOTT without errors it seems…
Did not test it yet in the Phoenix…
So why it behaved so strange in the Phoenix? Maybe some incompatibility in the Phoenix maybe my Dstb-1 was always on the edge of death.

I think the problems I was seeing in that video were a card on the edge of death too.

Exxos kindly sent me back the card I'd built for him and I was able to run DoTT for a few hours, albeit I wasn't interacting with it (just let the intro run and then sit on that screen -- I don't know if that's enough to foment the problem normally?).

I've not had a chance to really look into it futher -- I was going to try some of my experimental firmware builds on it.

I use the second software release.
So maybe the issues I had reported were due to a bad IC or something or aliexpress junk or semi bad soldering…

I think perhaps either the CPLD or SDRAM is a bit senstitive to handling. I'm fairly certain mine was in a partially failed state too.

Not had a chance for a proper side-by-side diagnosis yet.

Thanks for the update, though. I know the DMA isn't working correctly on the release build. I think I may try to offer two builds. A DMA-compatible one and a non-DMA 'fast' one, but we'll see.

BW

[JezC]

@Badwolf At some point I'll get at least one of my H5C1 boards working & then try to finish off the build of my DSTB1...then we might have more for comparison.

I think it's fitting a few of the caps plus programming it up that is still to be done, but I've no idea on how long that will take (severe lack of retro time at the moment).

Fingers crossed that I will get it done before CL3.0 ;)

[Steve]

I have a spare DSTB1 if anyones interested.

[Badwolf]

Work's been continuing looking into this.

Exxos kindly sent me back the board I built up for him and I've been using this. Sure enough, it behaves differently to my test board, so I think I've got problems with that original board.

That said, I did find signs of instability soak-testing Day of the Tentacle with the 20220531 and 20231016 firmwares (available from https://github.com/dh219/DSTB/tree/main/DSTB1/JEDEC), but the original 20220418 firmware has been rock solid.

This firmware has a few issues -- the LED doesn't work, it doesn't do TOS decoding or have the 16/8 switch and it makes no attempt to support DMA (no blitter into AltRAM) -- but it's not had any crashes when working with DotT and MiNT.

So thanks very much to @Oldskool for initially starting me down this route and providing a very good test platform with his DotT install (lots of IO + memory accesses).

I'll see if I can provide an updated firmware that supports AltRAM DMA but also passes the DotT test, but I have in the back of my mind that it may be we have to choose DMA or speed.

BW