2.2 Booster in MegaST4

[Bikerbob]

Apparently:

R150 is a resistor in the 16mhz line from the shifter.

So perhaps you could buzz-out with your multi meter onto resistors in that area, with the other end of the meter connected to the 16mhz line on the shifter... that might help you find it probably.

no, that part is ok, on the MEGASt I have to install the shifter buffer, so I connect the 16mhz line from the Booster PAD1 to pin4 on the buffer.

The other wire goes from the bottom CE pad on the MB to .... what was done on it when I got it was pin 39 of the LH side GAL. Is that right? I have no idea as I cannot find that connection in any discussions.

James

[Bikerbob]

Any pictures of a working install for connections in a MEGAST??

Anyone have any sort of install instructions for this?

This computer that it was in, is one of the ones with IMP chipset, so not ideal. ALSO I had to wire a L46 diode up to one of the pins of the shifter, so the shifter buffer would need that wired up as well..

This machine also DID have a blitter patch originally - In pulling the Booster and trying to get it back to normal, any blitter test of the 68000 cpu crashes in the diagnostics.

So I assume the blitter in this one actually needs the patch. A lot of boards get the wire patch on the underside.. this one does not have it? I think thats an alternative to the patch?? I dont have a patch to put into this machine, I would like to try and get it working with the booster (thats what the owner would like) But not sure this machine is a good candidate.

James

[exxos]

https://www.exxosforum.co.uk/atari/last ... /index.htm

If it had the blitter patch and removed it, then you probably haven't fixed the cut track under the CPU on th bottom of the motherboard? Or you haven't wired the booster in correctly.

At the bottom of this page lists the "bad blitters" which need the patch .
https://exxosforum.co.uk/atari/last/MEGAST/index.htm

But it's never been needed . And I have no idea how to fit or if it's even possible to fit with the booster. There might be side effects or the patch may cause malfunctions.

So I strongly advise you no mess about with the patch. If you have a later blitter then it's not needed. If you have a early blitter, either remove the blitter or find a latter blitter chip.

[Bikerbob]

Sounds good. Yes I need to do the line patch on the bottom of the board. I dont think that was ever done by the owner.

I will wire it the way I think it should.. and post some pictures. please give comment.

James

[exxos]

See here viewtopic.php?p=91724#p91724

[Bikerbob]

Sounds good. Yes I need to do the line patch on the bottom of the board. I dont think that was ever done by the owner.

I will wire it the way I think it should.. and post some pictures. please give comment.

James

OK, so back of board done, machine is back to 100% without the booster. Ran it for 6 hours on Diagnostic internal loop.

ALL good.

SO re-did the booster - got it added and I think everything wired up.. but I get a boot, not stable - funky screen.. I get Floppy access - but funky logo and then crash when trying to get to desktop. Same if I move the jumper and use the TOS on the board 1.4 - but seems a little better??? hard to say.

megaboost1.jpg

megaboost2.jpg

l46diode.jpg

BG pin.jpg

flicker.jpg

flick2.jpg

[exxos]

Why do you have 2 sets of ROMs running ?

Are you sure you not shorted out the 2 BG pads when soldering ?

The diode on the shifter is a untested mod. I don't know if that would screw up the GAL or not.

Have you tried 8mhz mode ?

Have you changed the bus pullup resistors ?

[Bikerbob]

Why do you have 2 sets of ROMs running ? I used the jumper on the booster to switch between 1.04 and 2.06??? -J5 right?

Are you sure you not shorted out the 2 BG pads when soldering ? YES - the upper pad is actually missing.. cant touch it.. not me :)

The diode on the shifter is a untested mod. I don't know if that would screw up the GAL or not. - THAT is factory.. I have seen it before; not often. If I remove that diode.. the machine will not boot; period.

Have you tried 8mhz mode ? - Not sure how to pick modes????

Have you changed the bus pullup resistors ? This board is 4.7k - So Dont think I need to play with those.. I am hoping I dont. If the owner wants me to get that deep into this, that will be up to him.

in the install STFM there is PIN13 of the left GAL to GND - DO I need to do that on the MEGAST?? I dont have that yet.

[exxos]

Pin 13 to 0v forces 8mhz mode.

You have to remove the motherboard ROMs. The jumper selects the bank in the dualtos chip.

As for resistors, read the bottom of the page https://www.exxosforum.co.uk/atari/last ... /index.htm

[Bikerbob]

Pin 13 to 0v forces 8mhz mode.

ahh so a switch then.

You have to remove the motherboard ROMs. The jumper selects the bank in the dualtos chip.

ok.. I'll remove the roms.

As for resistors, read the bottom of the page https://www.exxosforum.co.uk/atari/last ... /index.htm

Yep.. read that.

James