Mega ST2 and booster

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HigashiJun
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Mega ST2 and booster

Post by HigashiJun »

I bought some weeks ago the 16Mhz ST booster (rev. 1.4) along with a Mega ST DUALTOS PCB from Exxos and installed everything in my last toy, a Mega ST 2.

I have performed all the mandatory fixes except the 1772 pull ups.

My Mega ST boots fine in TOS 2.06 and behaves normally until I turn the blitter on, where it freezes.

It also displays four bombs when I want to access the FDD drive, with a disk inserted in, no matter if it is the original FDD, HXC or Gotek. Accessing the FDD with no disk inserted shows the usual warning message.

It was the same situation before I replaced the original SILS with 2.2K ones, so it is obviously not a bus resistor related issue.

Just for information, my machine works fine with the original CPU and the blitter on (and without the blitter patch).

I suspect the DMA needs some kind of buffering, like on the STEs, but I am not sure.

I will try to add the blitter patch on the booster and check if at least the blitter issue is solved.

Exxos does not support this booster on original motherboards, but if you guys have any clues or suggestions, they are welcome.
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rubber_jonnie
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Re: Mega ST2 and booster

Post by rubber_jonnie »

Under TOS 2.06 4 bombs generally is a floppy problem, for example if you boot a TOS 2.06 machine with no floppy you'll get 4 bombs. I suspect in this case you may have some timing issues.

You didn't say, but are these problems happening just at 16Mhz, or at 8Mhz too?
Collector of many retro things!
800XL and 65XE both with Ultimate1MB,VBXL/XE & PokeyMax, SIDE3, SDrive Max, 2x 1010 cassette, 2x 1050 one with Happy mod, 3x 2600 Jr, 7800 and Lynx II
Approx 20 STs, including a 520 STM, 520 STFMs, 3x Mega ST, MSTE & 2x 32 Mhz boosted STEs
Plus the rest, totalling around 50 machines including a QL, 3x BBC Model B, Electron, Spectrums, ZX81 etc...
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exxos
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Re: Mega ST2 and booster

Post by exxos »

If you had a blitter patch, did you repair the cut track under the cpu? Also what blitter exactly? Are the solder pads fully broken when blitter fitted?
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.
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HigashiJun
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Re: Mega ST2 and booster

Post by HigashiJun »

rubber_jonnie wrote: Tue Jul 13, 2021 3:37 pm Under TOS 2.06 4 bombs generally is a floppy problem, for example if you boot a TOS 2.06 machine with no floppy you'll get 4 bombs. I suspect in this case you may have some timing issues.

You didn't say, but are these problems happening just at 16Mhz, or at 8Mhz too?
I did not try to run my Mega ST with the booster at 8Mhz yet.

Something worth checking though...
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HigashiJun
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Re: Mega ST2 and booster

Post by HigashiJun »

exxos wrote: Tue Jul 13, 2021 4:18 pm If you had a blitter patch, did you repair the cut track under the cpu? Also what blitter exactly? Are the solder pads fully broken when blitter fitted?
Yes , the track under the CPU is repaired.

The blitter is a SGS 8937.

If you mean the two blitter enabling/disabling solder pads, they are not soldered.
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rubber_jonnie
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Re: Mega ST2 and booster

Post by rubber_jonnie »

HigashiJun wrote: Wed Jul 14, 2021 5:30 am
rubber_jonnie wrote: Tue Jul 13, 2021 3:37 pm Under TOS 2.06 4 bombs generally is a floppy problem, for example if you boot a TOS 2.06 machine with no floppy you'll get 4 bombs. I suspect in this case you may have some timing issues.

You didn't say, but are these problems happening just at 16Mhz, or at 8Mhz too?
I did not try to run my Mega ST with the booster at 8Mhz yet.

Something worth checking though...
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.
Collector of many retro things!
800XL and 65XE both with Ultimate1MB,VBXL/XE & PokeyMax, SIDE3, SDrive Max, 2x 1010 cassette, 2x 1050 one with Happy mod, 3x 2600 Jr, 7800 and Lynx II
Approx 20 STs, including a 520 STM, 520 STFMs, 3x Mega ST, MSTE & 2x 32 Mhz boosted STEs
Plus the rest, totalling around 50 machines including a QL, 3x BBC Model B, Electron, Spectrums, ZX81 etc...
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exxos
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Re: Mega ST2 and booster

Post by exxos »

HigashiJun wrote: Wed Jul 14, 2021 5:30 am I did not try to run my Mega ST with the booster at 8Mhz yet.
You need to try that.. There was a buffer board for the mega I now remember because the clocks were really bad.

see MEGA ST BUFFER BOARD INSTALL - MUST FOR ALL MEGA ST!
https://www.exxosforum.co.uk/atari/last/ ... /index.htm

but I have not made if for long time..
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.
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HigashiJun
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Re: Mega ST2 and booster

Post by HigashiJun »

rubber_jonnie wrote: Wed Jul 14, 2021 9:30 am
HigashiJun wrote: Wed Jul 14, 2021 5:30 am

I did not try to run my Mega ST with the booster at 8Mhz yet.

Something worth checking though...
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...
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HigashiJun
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Re: Mega ST2 and booster

Post by HigashiJun »

exxos wrote: Wed Jul 14, 2021 9:57 am
HigashiJun wrote: Wed Jul 14, 2021 5:30 am I did not try to run my Mega ST with the booster at 8Mhz yet.
You need to try that.. There was a buffer board for the mega I now remember because the clocks were really bad.

see MEGA ST BUFFER BOARD INSTALL - MUST FOR ALL MEGA ST!
https://www.exxosforum.co.uk/atari/last/ ... /index.htm

but I have not made if for long time..
Yes, I also heard that some Mega STs might be affected by with unstable bus issue.

But it seems there is no way to get the buffer board anymore... :cry:
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exxos
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Re: Mega ST2 and booster

Post by exxos »

You probably only need a Schmitt buffer on the 16mhz... But you need to be stable in 8mhz before moving onto other things.
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.
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