MEGA ST2 - "random" characters on the screen

[DominoTree]

Hey all, I've got a new MEGA ST2 here and I've gone through all of the mandatory fixes (DMA pullups, 2.2k bus resistors, etc) and I've still got an issue I've not seen before.

During boot, I get a bunch of unexpected characters on the screen as text is displayed. I also see similar behavior with running YAART from the cartridge port, although YAART itself runs through multiple cycles with no errors.

I'm running an Exxos PSU, and I've also swapped out the TOS ROMs to 1.4 but saw no change.

What's interesting here is that the "random" characters don't really change, it's pretty-much always the same thing in the same places. I found some dodgy solder joints on the shifter and got those sorted, but I haven't really noticed any graphical issues. (This is the MEGA ST2 with the Genlock that I posted about, but this happens with or without the Genlock attached)

One unfortunate thing is that I don't have a mouse/keyboard quite worked out yet, but it never seems to have issues booting to the GEM desktop, and once there everything always seems to be displayed properly (I've got a working prototype clone I built of an Eiffel hooked up to another ST that I need to transplant to get kb/mouse input working)

Any ideas where to look next?

4032-3024-max2.jpg (198.14 KiB) Viewed 3647 times

[exxos]

Does it have a blitter / blitter patch ?

[DominoTree]

Does it have a blitter / blitter patch ?

It's got a blitter but no blitter patch - I *believe* the date code here means this one should be okay without it, but I could rig one up to test - I think I have the parts here.

I've got another blitter I can swap in as well from a 1040STF (which works fine with no patch) if that would be worth a shot.

Here's what I've got (I removed the retaining clip from the blitter to take this photo)

4032-3024-max.jpg (527.17 KiB) Viewed 3642 times

[exxos]

It's got a blitter but no blitter patch - I *believe* the date code here means this one should be okay without it, but I could rig one up to test - I think I have the parts here.

8831 in my notes (bottom of page) https://www.exxosforum.co.uk/atari/last/MEGAST/index.htm says 8822 should be fine.. but as its close to both.. those dates on my site may not be 100% correct..

Might be easier just to remove the blitter and solder the 2 blobs and test without it...

[DominoTree]

It's got a blitter but no blitter patch - I *believe* the date code here means this one should be okay without it, but I could rig one up to test - I think I have the parts here.

8831 in my notes (bottom of page) https://www.exxosforum.co.uk/atari/last/MEGAST/index.htm says 8822 should be fine.. but as its close to both.. those dates on my site may not be 100% correct..

Might be easier just to remove the blitter and solder the 2 blobs and test without it...

Gave it a try with no blitter and it's still the same (with the same characters in the same places)

[rubber_jonnie]

I did also reply on FB as I saw it there first (Should really check here first!), but it looks like you have quite a few things loading in at boot time, including a font cache program.

I'd suggest you boot with just the hard disk driver and see if the problem happens, and if not. then slowly add in your other boot time programs one by one to see if a specific program is causing the issue.

I don't believe it's some kind of stuck key event as you said on FB you don't have a keyboard at the moment, or you'd see more characters. If you you don't have a keyboard coming and need a keyboard solution I'd recommend an Eiffel from Gossuin.be.

I'd also suggest before using your good SD card/Ultrasatan on an unknown machine that you back up your card first. I've had unknown machines corrupt my SD cards before the mandatory fixes were done, so it's simple to have an image you can just re-write to the SD if it all goes wrong. If you're using Windows, I'd suggest Win32DiskImager.

[DominoTree]

I did also reply on FB as I saw it there first (Should really check here first!), but it looks like you have quite a few things loading in at boot time, including a font cache program.

I'd suggest you boot with just the hard disk driver and see if the problem happens, and if not. then slowly add in your other boot time programs one by one to see if a specific program is causing the issue.

I don't believe it's some kind of stuck key event as you said on FB you don't have a keyboard at the moment, or you'd see more characters. If you you don't have a keyboard coming and need a keyboard solution I'd recommend an Eiffel from Gossuin.be.

I'd also suggest before using your good SD card/Ultrasatan on an unknown machine that you back up your card first. I've had unknown machines corrupt my SD cards before the mandatory fixes were done, so it's simple to have an image you can just re-write to the SD if it all goes wrong. If you're using Windows, I'd suggest Win32DiskImager.

It does the same thing without the hard disk attached, booting from cartridge, so it's not something being loaded at boot.

I've got a microcontroller-based prototype that should work to give me kb/mouse, I just haven't taken the time to wire it to the MEGA yet (it's currently handling input for an STF)

Got plenty of backups floating around here too

[DominoTree]

Tried with another known good DMA, another known good GLUE, another known good MMU, another known good shifter, and with/without blitter (two different ones) and it's still doing the same thing. Guess this is gonna get really interesting

[TheNameOfTheGame]

Could it be some sort of IKBD controller error?

[exxos]

During boot, I get a bunch of unexpected characters on the screen as text is displayed. I also see similar behavior with running YAART from the cartridge port, although YAART itself runs through multiple cycles with no errors.

That sounds like pullup problems, id check all the address and databus on CPU to make sure you have 2.2K on them all...