2.2 Booster in MegaST4

[LarryL]

The best machine for this booster to go into is a STFM I assume?

The 70789 is the most stable.

Though don't you have a H5 you could try the booster in ? at least then you will know that is functioning correctly or not. If you want to do that i'll figure out how to fit it in. If you can get it working on the H5 then you know the problem is inherently with the MEGA. if it does not work on the H5, then you know the problem is on the booster (at least anyway). Either way something would be ruled out.

maybe of interest re stability of Mega STs...
I recently added a "TF536 ST edition" into my Mega ST
It is a C103277 Rev2.2 - no IMP, all Atari chips, Blitter removed
I did all the "mandatory fixes" upfront
runs rock-stable, incl. IDE from the TF, Floppy and external UltraSatan via ACSI

so, seems there are stable Mega ST setups with boosters - but maybe I am just lucky

[exxos]

maybe of interest re stability of Mega STs...
I recently added a "TF536 ST edition" into my Mega ST
It is a C103277 Rev2.2 - no IMP, all Atari chips, Blitter removed
I did all the "mandatory fixes" upfront
runs rock-stable, incl. IDE from the TF, Floppy and external UltraSatan via ACSI

so, seems there are stable Mega ST setups with boosters - but maybe I am just lucky

Thanks for the information. Though yes, if you have done all the fixes then it fixes all the currently known problems with most machines. So you will of course stand the best chance of fitting accelerators and such without them malfunctioning.

I think somewhere in Atari's own documents it said generally machines can tolerate one IMP chip. but this is just how unstable and problematic machines can be when they are in "stock" form.

Even adding something like a DIP to PLCC CPU adapter is enough to cause problems even at stock speeds. So then when you add an accelerator like mine which speeds up ROM access to 16MHz or above. Is just not going to work reliably without doing all the fixes.

Even running the accelerator on stock speeds malfunction. Though I presume a lot of accelerators only use the bus that stock speeds are maybe it is not always as noticeable in some cases. But in any case I've always found repeatedly similar problems on various machines where the solutions were also common. That is where the mandatory fixes of basically born from.

IIRC the ST536 isolates the ST bus during fast-rom access. So it is possible it may be inherently more tolerant to bus stability issues as it is not accessing anything on the ST bus any faster than stock speeds. But again, it is very hit and miss depending on multiple factors.

[Darklord]

so, seems there are stable Mega ST setups with boosters - but maybe I am just lucky

Same situation here. I have an AdSpeed accelerator, Cloudy TOS decoder board, and
the Lightning-ST USB upgrade, all stacked up in my Mega ST4. Point of interest, I've
never done any "required" upgrades on it at all. It did start out as a Mega ST2 and was
upgraded to 4 megs, as well as going from TOS v1.2 to TOS v1.4.

Maybe I'm just lucky too.

[frank.lukas]

My favorite Atari ST is a Mega ST and i have never had any problems with various accelerator cards such as a HBS240, HBS640 and a PAK68/3 ...

[exxos]

Where the PAK creator must have found bus stability issues as well, hence the buffer board.

Capture.PNG (109.28 KiB) Viewed 5293 times

But getting back to the context of this thread, we don't know if the booster is even operational at this point.

[Bikerbob]

Yep.

Remove the H5 CPU and ROM.
Plug the booster into a 5V slot.
Set the booster to TOS206.
Connect the 16MHz wire direct to the shifter pin 39 on the H5.
The BG wire (which you currently have soldered to the blitter pad) needs fitting to a different 5V port on pin 11.

That should be all you need to get working then.

Fired right up - no issues, also tested IMP Shifter in the H5 - worked fine as well. So its the MegaST not stable enough for the booster. FINE, I told my buddy he was fine with it. Bummed, but said it is what it is. He has a STFM he might get out and put it in there.. for now. This project is done.

At least all the hardware works.. just not together.

James

[exxos]

Fired right up - no issues, also tested IMP Shifter in the H5 - worked fine as well. So its the MegaST not stable enough for the booster. FINE, I told my buddy he was fine with it. Bummed, but said it is what it is. He has a STFM he might get out and put it in there.. for now. This project is done.

At least all the hardware works.. just not together.

Good the booster has tested good on the H5. Sorry you're giving up. Though like I said before, unstable in 8MHz mode can only be the bus resistors etc, at least what I can think of. If that is the problem, then swapping to a STFM probably won't help either.

[Darklord]

Hmm, I just wanted to point out that I wasn't contradicting in any way, shape, form or fashion
what Chris says about the Mega ST's problems. He has far greater experience with these things
than I do so I would accept it as the gospel truth.

I've had 3-4 Mega ST's over the years and weeded them out, keeping the best one for use with
my BBS. I'd be willing to bet good money that if I had stacked all the upgrades I have in them,
odds are that they would have showed problems/symptoms in line with Chris's assessment.

I was being honest when I said I was lucky enough to get a stable one.

[exxos]

@Darklord I don't think what anyone says is in question. These machines are nothing short of a lottery.

I always found the 70789 type boards to be the most stable. Others not so much. But also as pointed out in my research, I could have several same revisions of board which seemingly work fine, then several others which don't.

It's even more of a lottery when you push 16mhz or 32mhz on the ROM access for example. The ST bus simply can't cope. But during my testing even stock machines can trip up at random times. It can be hours or days until it trips up. It's why I added a loop test in GB6 which saves the loop count to floppy. If it crashed once in a 48 or more hour run, I would get to the bottom of it. The conclusions and fixes were always the same.

I know people love their MEGA machines. I'm not hating on any of them. Just I found them to be the least stable machines in all my testings.

As we drifting off topic and the thread seems done. I'll lock it up.