Mega ST 1 Dead Blitter?

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mmx01
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Mega ST 1 Dead Blitter?

Post by mmx01 »

Hi,

Bought off ebay non working Mega ST 1, PSU was dead which I repaired but short after I ran into another issue (first time seeing such behaviour).

When no storage device is connected (i.e. ASCI2SD / FDD) it boots to GEM. Mouse and keyboard work, passes RAM test etc. As soon as I attach working/tested say FDD, the machine will no longer boot. It will stuck with white screen. Thought FDD controller or DMA is to be blamed but no... both check out in my STFM. After a lot of probing and chip testing I was nowhere.

Resorted to test cartridge and I discovered blitter while fitted fails the test both short & long = error, no blitter detected. Upon soldering open jumpers (like there's no blitter) and connecting drilled trace for blitter patch, machine came back to full life and I/O is working. Reads floppies and ASCI2SD no problem, no freezes.

Pretty much 99% sure blitter is dead... or something else driving it? (continuity is okay), moved blitter to STFM opened jumpers W3/W4 same behaviour machine stops working with any FDD/ASCI2SD attached.

Anyone seen something like that? Any source of blitters for STs which did not dry out? I am based in EU but shipping from US could be an option too. Blitter is ST one 9018.


Regards,
Mariusz
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exxos
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Re: Mega ST 1 Dead Blitter?

Post by exxos »

Blitters are near impossible to find these days :( Have you simply cleaned the pins and such ? if your machine has the blitter patch installed you can probably remove it as sounds like you have a later blitter chip anyway.
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viewtopic.php?f=17&t=1585 Have you done the Mandatory Fixes ?
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mmx01
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Re: Mega ST 1 Dead Blitter?

Post by mmx01 »

I tested with patch on and patch removed in Mega ST 1 but also ported it to 520STFM so re-soldered PLCC68ish socket and there was no need to connect any other traces than 2 blobs I understood. For 520STFM I did not port the patch itself reading re. blister serial numbers (mfg dates). All bad solder joints should also be fixed with this but it doesn't work in either of machines.

What is interesting is that machine with blitter fitted but blitter IC removed (solder blobs not reapplied) should not boot at all? Can someone confirm this? Because then it wouldn't be completely dead as it boots but without I/O devices attached, hard to see if it pokes DTACK since it can be any of other ICs while in circuit.

Found one blitter on ebay but it is more than the price I paid for entire machine otherwise quite functional now. Since it is Mega perhaps fitting accelerator is an option, not the same but some performance improvement, not sure what to do next.

Also with blitter installed in 520STFM, it boots to test cartridge and GEM without IO devices. Connecting via serial:

I6 Testing Bus Error handling
No (I6) error
Keyboard failed, connect RS232 terminal
Enter letter(s), and RETURN: G
Testing Blitter
No Blitter installed
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exxos
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Re: Mega ST 1 Dead Blitter?

Post by exxos »

When removing the blitter patch did you reconnect the trace under the CPU ?
https://www.exxosforum.co.uk/atari/ All my hardware guides - mods - games - STOS
https://www.exxosforum.co.uk/atari/store2/ - All my hardware mods for sale - Please help support by making a purchase.
viewtopic.php?f=17&t=1585 Have you done the Mandatory Fixes ?
Just because a lot of people agree on something, doesn't make it a fact. ~exxos ~
People should find solutions to problems, not find problems with solutions.
mmx01
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Re: Mega ST 1 Dead Blitter?

Post by mmx01 »

Yes, otherwise it wouldn't boot at all with patch removed. Looks like otherwise BGACK wouldn't get its way to the CPU. Was easy to find which one it is as it was drilled through.

Just checked things further, with motherboard configured for blitter (solder joints removed) and also blitter IC removed physically I get the same result - it freezes on I/O access but otherwise is happy to boot to GEM when only mouse and keyboard are attached. Quite easy conclusion then, blitter chip is a paper weight :(
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Re: Mega ST 1 Dead Blitter?

Post by exxos »

This sounds very familiar.. I don't know if anyone else can remember it was having similar troubles with the keyboard and it not booting not long back?

You may want to search through the hardware issues section for mega ST faults..

EDIT:

It might have been this one I was thinking of https://www.exxosforum.co.uk/forum/viewt ... =23&t=3908

Not to the point of not booting, but random stuff going on (which could cause a machine not to boot) but a quick skim , doesn't seem like it got solved.
https://www.exxosforum.co.uk/atari/ All my hardware guides - mods - games - STOS
https://www.exxosforum.co.uk/atari/store2/ - All my hardware mods for sale - Please help support by making a purchase.
viewtopic.php?f=17&t=1585 Have you done the Mandatory Fixes ?
Just because a lot of people agree on something, doesn't make it a fact. ~exxos ~
People should find solutions to problems, not find problems with solutions.
mmx01
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Re: Mega ST 1 Dead Blitter?

Post by mmx01 »

C302183-002 STE integrated glue + blitter are much more accessible. I guess if that would be a matter of a simple PCB adapter it would have been done a long time ago to port this to older ST machines? Hope is strong.
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Icky
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Re: Mega ST 1 Dead Blitter?

Post by Icky »

mmx01 wrote: Wed Nov 03, 2021 9:01 am C302183-002 STE integrated glue + blitter are much more accessible. I guess if that would be a matter of a simple PCB adapter it would have been done a long time ago to port this to older ST machines? Hope is strong.
This has been discussed a few times but back porting the STE integrated chip to an STFM is nigh on impossible. There is however efforts to recreate the blitter in FPGA plugin module. It's a long thread but nearer the end you can see we are at 98% off the original Blitter in terms of GEMBench scores.

Blitter Recreation Thread
mmx01
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Re: Mega ST 1 Dead Blitter?

Post by mmx01 »

That is a wow :), recognized GLT voltage level shifters as gateway to old 5V world. Will definitely read through as have some Max IIs and Cyclone IVs around from another project.
tzok
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Re: Mega ST 1 Dead Blitter?

Post by tzok »

Last year (or maybe a little more) I wanted to have a Blitter enabled 1040STF, and I was able to buy one on a local (Polish) forum, so maybe you're looking too far away from home (I guess) ;)
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