16mhz booster install in a mega 1

[Badwolf]

11 bombs is a line-F error, IIRC.

That normally means (on machines without FPUs) that it's tried to read something and got nothing back (comes through as FFFF, which if the CPU tries to execute it results in a line-F error).

That could be down to intereactions with that IMP chipset, or it could be something as simple as the ROM not being quick enough (I think Exxos' booster tries to read the ROM at 16MHz). Just double check you have the fast ROM there?

Does it work OK at 8MHz?

BW

[RB80atari]

Hi BW,

I dont know if its the fast rom? There are no specs on exxos webstore (Rom: Item# 0050)
I showed a pic of it on the first post on this thread?

But no the booster doesnt work at 8mhz either (just as a decoder) with the mega dual tos board. At least not for me anyway.
I removed the wire from the 16 mhz input on the booster to pin 39 on the shifter, bridged the 2 pads on the booster (disable booster) left the CE wire connected and then retried it just as a decoder and neither 1.04 or 2.06 will boot, both bomb same as pics above.

So, yeah i removed all of it.
Put my 2x tos 1.02 roms back in, put the cpu back in, boots up first time, no problem at all and ive had no problems since.
I dont like to blow my own trumpet, but the solder work i did on the motherboard was perfect, the cpu socket is perfect.

I did try to troubleshoot it a bit, did continuity checks on the PLCC socket, all seemed fine, did the same on the booster, checked the bottom header pins connect ok to top socket and all fine too, so not sure what to think really.
I also have the exxos 4mb MMU memory upgrade which also plugs into the shifter socket, but i dont expect that will be affecting it.

I know Chris has said he doesnt support the booster on the Mega, so obviously there were problems with it.
Pretty annoying i have to say....

11 bombs is a line-F error, IIRC.

That normally means (on machines without FPUs) that it's tried to read something and got nothing back (comes through as FFFF, which if the CPU tries to execute it results in a line-F error).

That could be down to intereactions with that IMP chipset, or it could be something as simple as the ROM not being quick enough (I think Exxos' booster tries to read the ROM at 16MHz). Just double check you have the fast ROM there?

Does it work OK at 8MHz?

BW

[Badwolf]

But no the booster doesnt work at 8mhz either (just as a decoder) with the mega dual tos board. At least not for me anyway.

That's really odd. Yes, the Mega can be a bit flakey (I've not tried my booster in my Mega yet -- it's on the list), but if it doesn't work at 8MHz, then something else is going on.

I know that 16MHz line can be really tricky. @Steve, I think, has a good post somewhere about experimenting with routeing of it on an -FM motherboard (IIRC), but you should be able to have that disconnected entirely and still run in 8MHz mode, I've have thought.

It's a shame, but for some reason the ST series really is finicky when it comes to expansions. Timings tolerances are just too tight, perhaps? I'm still trying to find a way to get my board (which works superbly on my STFM and my STE and another users' various machines) to work on Oldskool's machines.

Have a look at the effort put into PiStorm. It's so hit and miss where it works and where it doesn't.

Then you see Amiga users slap any old thing into their boxes and it works like a charm!

It's a crapshoot!

BW

[RB80atari]

Id have thought tos 1.04 would boot ok with the mega st dual tos board, as that doesnt need any decoding? But it gave me bombs.
I didnt try it on its own without the decoder/booster connected
I had to cut the header pin marked CE off the dual tos board to hook it up to the decoder, if i run it on its own without the decoder just as a rom switcher i assume i need to reinstate that pin?

But no the booster doesnt work at 8mhz either (just as a decoder) with the mega dual tos board. At least not for me anyway.

That's really odd. Yes, the Mega can be a bit flakey (I've not tried my booster in my Mega yet -- it's on the list), but if it doesn't work at 8MHz, then something else is going on.

I know that 16MHz line can be really tricky. @Steve, I think, has a good post somewhere about experimenting with routeing of it on an -FM motherboard (IIRC), but you should be able to have that disconnected entirely and still run in 8MHz mode, I've have thought.

It's a shame, but for some reason the ST series really is finicky when it comes to expansions. Timings tolerances are just too tight, perhaps? I'm still trying to find a way to get my board (which works superbly on my STFM and my STE and another users' various machines) to work on Oldskool's machines.

Have a look at the effort put into PiStorm. It's so hit and miss where it works and where it doesn't.

Then you see Amiga users slap any old thing into their boxes and it works like a charm!

It's a crapshoot!

BW

[Badwolf]

Id have thought tos 1.04 would boot ok with the mega st dual tos board, as that doesnt need any decoding? But it gave me bombs.
I didnt try it on its own without the decoder/booster connected
I had to cut the header pin marked CE off the dual tos board to hook it up to the decoder, if i run it on its own without the decoder just as a rom switcher i assume i need to reinstate that pin?

Hmm. I hadn't thought about decoding being the source of the problem, but perhaps if your pull-up isn't strong enough there could be some bus contention going on.

But to answer your question -- I don't know. I do have a Mega dual TOS board, but haven't built it yet.

On my -FM, here's the mod I did to support both internal and external decoding, but I don't know if that helps on that board at all.

IMG_8338.jpeg

Basically, added a pull-up to the ROM chip's CE line (that may be worth doing anyway -- see above) and added a second diode coming from the motherboard's CE line so the ROM's line can be pulled low by either the motherboard or an external decoder. That pull-up needs to be sufficiently sized to de-assert the ROM before the next bus cycle, though.

Which is what just crossed my mind up there.

BW

[exxos]

A good spot @Badwolf The STFM dualtos indeed has that modification.
https://exxosforum.co.uk/atari/last/tos ... htm#DTSTFM

The MEGA dualtos shouldn't need it.

I think the dualtos board should be tried on its own initially (without booster), this would involve refitting the cut CE pin (or patching it elsewhere), as the dualtos board on its own uses GLUE decoding as normal.

Also that cut CE pin when using the booster, need to make sure its not shorting out on the IC socket. As the booster drives that pin and does 104/206 decoding itself, if the CE pin is shorting to the IC socket, that's not going to help.

All the ROMs I sell are 55ns. So no problem when buying from the store.

[RB80atari]

Thanks for the info and suggestions BW.

Exxos, the CE pin on the dual tos board isnt shorting against the socket its been completely removed, the CE wire to the booster was then soldered from the CE pad on the top and run over to the booster.

OK i will try the dual tos board on it own, the cut CE pin is pin 20, right?
I only have 2 socketed rom slots on my mega 1, the other 4 are not populated and all the through hole pads all filled with solder, but your saying i can run a wire from CE on the dual tos and just solder it to a free solder pad, pin 20 on any of the unpopulated rom slots?

[exxos]

Just wire link the CE pad to the LS11 output (pin 12) Or just put a new pin in the pad, whatever is easier.

Capture.PNG

[RB80atari]

Yep, tried that. Dual TOS board now boots into TOS 1.04 no problem.
So some incompatability with the motherboard or something wrong with the booster/decoder?
When the booster part didnt seem to be working yesterday, i did remove the 16 mhz wire between the booster and the shifter and also bridged the 8mhz pad on the booster (to disable it and just use it as a decoder) with CE still connected between them and 1.04/2.06 would not boot? both gave me bombs

Just wire link the CE pad to the LS11 output (pin 12) Or just put a new pin in the pad, whatever is easier.


Capture.PNG

[exxos]

Yep, tried that. Dual TOS board now boots into TOS 1.04 no problem.

Good news.

So some incompatibility with the motherboard or something wrong with the booster/decoder?

The decoder can only decode the address its given/sees. It's why the bus pullups needs to be changed as the bus is unstable, even more so at 16mhz. But I have never known (that I recall) problems after doing those mods with running in 8MHz. Generally it's a bad connection, or try swapping the IMP GLUE & MMU for something else and try again. But IMP I think was mostly having issues at 16MHz. But maybe your board is even worse than the ones I tested. Its difficult to know.

When the booster part didn't seem to be working yesterday, i did remove the 16 mhz wire between the booster and the shifter and also bridged the 8mhz pad on the booster (to disable it and just use it as a decoder) with CE still connected between them and 1.04/2.06 would not boot? both gave me bombs

I would suggest fluxing the CPU socket on the booster and reflowing it. Also wipe the CPU and booster pins with IPA. I can only assume you have a bad connection as in 8mhz nothing is boosted, it all runs at the stock 8mhz. There is no real difference from the GLUE doing decoding to the booster. The 16MHz wire isn't needed if running 8MHz.