How to investigate failing Blitter access while CT60 active?

[foft]

Possibly already answered but how are you powering the Falcon?

If using the new CT63 you can’t directly use the 3.5mm drive output, since the 5v voltage drop is too much. If so add a decent copper wire from 5v on the atx to 5v output.

[pakman]

I would like to inspect this properly and not just try random things.
So that is why I have opened this thread, to avoid just random things and get advice about more systematic approach.

Interesting. If you consider visiting OFAM 2024 at Münchberg (and if the problem still exists by then..) we could have a joint debugging session with scope and logic analyzer over there.

[mikro]

Thanks for the replies, guys.

@Badwolf I think you got most of it right, so thanks for the pointers. This is most likely where I start, I'm still hoping to drag Jookie to my place for this, it should definitely speed things up a bit.

@foft it's Centuriontech's CT60PSU, so power lines directly to the motherboard (and the 3.3V to the CT63, of course). But that's also a good hint, to check the voltages. Maybe the new CT63s are more sensitive and those signals BW mentioned are weaker than they should be.

@pakman Holger, nice to see you here! I am considering OFAM for sure (had a great time last year!) so your kind offer is definitely tempting. I'm just afraid whether you wont look like my private fixing service, last year my TT, this year my Falcon.

Will keep you posted (it's not my top priority right now but I did disassemble the Falcon on my workbench).

[Rustynutt]

One thing I had in mind was to create a custom CT60 TOS image which would have the first instruction accessing the Blitter and then just stop (or enter a loop with flashing screen so I would see whether the machine froze or not).

That way I could hook on some signals immediately after reset but still, no clue what should I check.

Was it Rustnut? Who was experimenting with over clocking their Falcon bus. He disabled blitter in TOS because the blitter would crash if the bus was overclocked. This is why the phantom and nemesis had programs that would enable it once TOS was booted. Apparently the Atari logo would actually use blitter, which is why bus boosting can't be done 'by default' and had to be enabled later.

I dunno if that info helps you.

Yes, it was set to 8MHz (1/2 bus in TOS, new ROM burned).

[viking272]

@pakman Holger, nice to see you here! I am considering OFAM for sure (had a great time last year!) so your kind offer is definitely tempting.

Did you take your Falcon to OFAM for some personalised fixing

[mikro]

Unfortunately I did not (although I really wanted to make the trip!), too many things going on atm.

I plan to return to this problem after the Silly Venture party in December.

[Rustynutt]

from my experience, the BLiTTER was completely stable with overclocked bus to 20MHz ( and 40MHz 030 in my case ) and was unstable wit 24/50MHz bus (48/50MHz CPU)

Yes mine too .. but what I'm trying to say is that the blitter can't be overclocked on the initial atari logo screen. This is why bus overclocking can't be done permanently, and has to be done by software once TOS is loaded.

Rustnut got around it by patching TOS to not enable blitter at boot ... why this is the case, I cannot remember.

I might be getting confused ... but it's something I read about during Rustnut's trials.

Actually not disabled, just set to 1/2 speed. On a "Stock" Falcon, booting at 60MHz is possible, but not really necessary as 25/50 provides that alluring VGA TC mode.
This works on the AB040 as well, but of course doesn't work on the CT as it actually does disable the BliTTer. Fastest I've been able to run the bus with my CT is around 46MHz. The AB limit is 44MHz, stable.
Anyway, with the BlITTer at 1/2 bus, the Falcon can get to the point of loading NVDI.

[mikro]

of course doesn't work on the CT as it actually does disable the BliTTer

It's incredible how this is misinformation is repeated over and over. The Blitter can't be switched off, there's nothing to switch.

The only thing related to that is VDI's usage of the Blitter, which is hardcoded in TOS 4.x. So no, neither CT60 nor CT60 TOS disables the Blitter, it is used up to the point NVDI (or similar) is loaded.

[Rustynutt]

Ok, CT boot screen doesn't use the BliTTer at boot
My point was, on a NON CT machine, one can have a 30/60 MHz clock at boot, and setting in TOS the BliTTer at 1/2 CPU, there are no issues when the Atar logo is BliTTed to the screen. After NVDI loads, switch it back if desired.

[Rustynutt]

But realize this isn't really a thread for this info. Was following up on a statement Steve had made.