Mega ST2 and booster

[rubber_jonnie]

With any booster I'd always recommend testing at the original CPU speed first. That way you can verify it is working under standard conditions.

And that is a wise recommendation...

:)

[HigashiJun]

Ok, so tried the booster with the SEL pin connected to GND.

There is an improvement with the blitter, as it does not freeze the machine when enabled, but incredibly slows down the display of GEM windows.

When I manage to disable the blitter, everything goes back to normal.

The floppy disk drive is recognized and works great with no disk inserted in, but once I try to access a floppy, I have a row of bombs on the screen.

[rubber_jonnie]

Might be worth checking the Blitter pads with a microscope to make sure there aren't any solder whiskers shorting them.

Also, do you have a diag cartridge? I used one of these to help track down a floppy problem with a Mega, as it allows you to run tests repeatedly and consistently, something important when tracking down faults.

Has a couple of good Blitter tests as well as a suite of floppy tests. You may also want to test the RAM thoroughly.

I did some FDD repairs in this thread: https://www.exxosforum.co.uk/forum/viewt ... hilit=mega

Might help, worth a try, mine turned out to be the DMA that was giving the floppy problems.

One thing you didn't mention was if it all worked just fine before you did the upgrade? Also, does it work with the other version of TOS that's installed, which I am assuming is 1.04?

[exxos]

There is an improvement with the blitter, as it does not freeze the machine when enabled, but incredibly slows down the display of GEM windows.

When I manage to disable the blitter, everything goes back to normal.

That sounds really strange. I suggest you continuity check from the CPU to the blitter make sure there is not a bad connection somewhere.. Start with pin 10 of the CPU (DTACK) to pin 27 on the blitter.

[HigashiJun]

One thing you didn't mention was if it all worked just fine before you did the upgrade? Also, does it work with the other version of TOS that's installed, which I am assuming is 1.04?

Everything is normal when I put back the original CPU (without blitter patch) and TOS 1.04.

FDD, Gortek or HXC work as expected, and blitter also works perfectly.

I made several loop tests with Gembench and there was no problem at all.

I only have those weird issues with the booster installed.

[HigashiJun]

That sounds really strange. I suggest you continuity check from the CPU to the blitter make sure there is not a bad connection somewhere.. Start with pin 10 of the CPU (DTACK) to pin 27 on the blitter.

I wlll try the booster with the blitter patch on and also perform a continuity check tomorrow, as I am working today on my new STE board and your V1 plug-in booster... :D

[exxos]

I wlll try the booster with the blitter patch on and also perform a continuity check tomorrow,

The blitter patch has never been attempted with the booster.. I don't know how it would even be fitted.. but with a recent blitter you don't need it...

See ATARI TECHNICAL NOTES ON THE BLiTTER

https://www.exxosforum.co.uk/atari/last/MEGAST/index.htm

[HigashiJun]

I wlll try the booster with the blitter patch on and also perform a continuity check tomorrow,

The blitter patch has never been attempted with the booster.. I don't know how it would even be fitted.. but with a recent blitter you don't need it...

See ATARI TECHNICAL NOTES ON THE BLiTTER

https://www.exxosforum.co.uk/atari/last/MEGAST/index.htm

I read your interesting article some time ago and that is why I removed the blitter patch from my Mega ST.

I just want to test if only the blitter issue could be solved by adding the patch. I will not even solder it, just make it hold with some masking tape.

[exxos]

I will not even solder it, just make it hold with some masking tape.

That really does not sound like a good idea..

Does your machine work without the booster and without the blitter patch ?

[HigashiJun]

I will not even solder it, just make it hold with some masking tape.

That really does not sound like a good idea..

Does your machine work without the booster and without the blitter patch ?

Could it be harmful for some components ?

The Mega works flawlessly without the booster and without the blitter patch.