Hi, why don't use both revisions of the MT-32 firmware if you worry about compatibility ? 😀
I haven't checked what kind of EPROM my MT-32 uses, but the Amiga folks did use two kinds of Kick-Start (1.03/2.x) since eternity.

In essence, if the unit uses something like an 27128 EPROM, you can burn both firmwares into one larger EPROM (27C256).
After this, by either attaching A14(?) to VCC or GND, you can force an EPROM to either enable the lower and higher adress space.
It's a bit like dual-booting on PC (enabling one of the partitons or HDDs).. 😀

Anyway, it's just an idea that comes to mind - Please double check what I said, before doing any modification, okay ? 😉
The MT-32 is/was an awesome piece of hardware. Even by todays standard, it is still awesome (it's a real synthesizer).

Alternatively, you can also use a Raspberry Pi with Munt as an MT-32 replacement.
From my understanding, if you own a real MT-32 anyway, you can also use an emulator in place of the real thing.

Well, it's academic really, because there's probably no point in using an old firmware. What you're suggesting may be possible, but there is the added complication of there being two EEPROMs (odd/even).
I'm mainly curious about others' experiences. That, and it could be useful and save someone time if they're having trouble -- also part of the reason for my post; now there's at least one mention online about the MT-32 1.0.5 firmware and Prince of Persia... 😀

Found this:

MT-32 1.04 unknown, initial release?

MT-32 1.05 Volume knob changes are now interpolated as opposed to directly applied to the data, allowing for much smoother volume changes when using the knob

MT-32 1.06 Rhythm selection Bender Control is now reset when MIDI All parameter reset is recieved, and when MT-32 Active Sensing is not received. Displays will not change, even when a Display Change exclusive MIDI message is recognized, unless the current mode is Master Volume input mode (e.g. Power-up default)

MT-32 1.07 Fixes a bug related to specific values in uninitialized sram on startup causing the unit to act bizarre.

MT-32 2.04 Unknown (possibly the first 2.x mt-32 rom. contains changes boosting the level of the la32 chip to de-necessitate the 14-bit hardware dac-hack, and changes related to the demo mode expanded rom, and the changed hookup of the volume knob, and possibly other changes related to the MT-32 2.x pcb)

MT-32 2.05 Unknown

MT-32 2.06 Unknown

MT-32 2.07 Unknown

https://en.wikipedia.org/wiki/User:Lord_Nightmare

^Thanks a lot for the details! ^^

InbetweenDays wrote on 2019-06-13, 04:12:

Well, it's academic really, because there's probably no point in using an old firmware. What you're suggesting may be possible, but there is the added complication of there being two EEPROMs (odd/even).
I'm mainly curious about others' experiences. That, and it could be useful and save someone time if they're having trouble -- also part of the reason for my post; now there's at least one mention online about the MT-32 1.0.5 firmware and Prince of Persia... 😀

Hi! Thanks for your response and sorry for the delay.
I didn't notice that you wrote back. Using the method on a pair of EPROMs should also work, I think.
Either by using a six pin switch, a relay or *maybe* by wiring both chip's address pins together to ground/VCC (not checked, be careful)..
Anyway, I found some more information on the matter. Apparently, a few games from Sierra and Dynamix did exploit firmware bugs of the original firmware.
I don't know if it is true, but it is mentioned here -> https://things.bleu255.com/moddingfridays/Munt

Edit: Typos fixed.