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MEGA ST upgrading TOS

Posted: Tue May 14, 2019 11:04 pm
by JezC
I've just opened up my Mega ST4 to see what my options were to upgrade the TOS version (currently 1.02)...mine currently has the two TOS ROMs fitted & the other 4 ROM sites are empty (no sockets present, holes appear to be free of solder).

I really want to upgrade it to TOS 1.04 as a minimum (it has a Megafile 60 with it & so all those bug fixes would make sense) but I'm not sure if my best/easiest option is to fit 6x ROMs (and swap some solder links?) or to just replace the 2x ROMs (and if so, what parts do I need)?

My main use will be MIDI s/w (Cubase/Notator & possibly Logic) - I have the various dongles and Midex+/Unitor/Unitor 2 & even a Combiner so that might limit some of the options.

Any suggestions will be most welcome - I'm working on saving up some funds to order some goodies & feed Harry (the wish list is way beyond my available funds sadly) but I do have a programmer as a short-term solution.

Re: MEGA ST upgrading TOS

Posted: Wed May 15, 2019 7:11 am
by PhilC
Morning Jez,

The easiest option is to fit one of exxos's rom boards in the place of the two Roms, don't forget to order the eprom as well :D

It depends if your CPU is socketed but you could also add a booster fairly quickly if it is, or even get involved with the IDE booster testing which has the ROM switcher built in.

Re: MEGA ST upgrading TOS

Posted: Wed May 15, 2019 8:23 am
by JezC
Hi Phil,
Yes that's one option I'm considering, funds being the biggest issue preventing me this month. :cry:
If the 2 chip UK TOS 1.04 were in stock then that would be the simplest way to go, but alas there are none ATM. :cry:

68k isn't socketed sadly and I'm not yet confident enough to risk adding one, need to practice on a faulty STFM first. :roll:

I like the sound of the IDE board & also the ROM + RTC option...but both are more appropriate to one of my STF/STFMs.

I will see if I can get some blank PROMs or something.

Re: MEGA ST upgrading TOS

Posted: Wed May 15, 2019 10:28 am
by exxos
The schematics will show the jumper settings from 2 chip to 6 chip.


ROMSPLIT ( can't find it in our software section )


TOS104 will almost never be in stock in my store. Only source for them is old machines, and I rarley buy any these days, and the boards I do almost never have 104. Its why I make the various ROM adapter boards.