Roland MT32 (original) memory retention?

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Roland MT32 (original) memory retention?

Postby siriushardware » Mon Jul 10, 2017 9:47 pm

Definitely more of a MIDI hardware question than an Atari question, but I bet many an ST MIDI setup started or expanded with the original black-wedge Roland MT32 tone module with its eight MIDI channels + PCM drumkit. Along with maybe the Yamaha FB-01 or Yamaha TX-81Z.

By modern standards the sound of the MT-32 was quite 'thin' even when using its full 32-part multitimbral capability but its major weakness was that although fully editable, the voice / part / patch memory was volatile. You could save your carefully made patches with the same editor program that you were using to do the editing with - Dr. T or some such, but as soon as you switched the unit off - gone. You could reload them again using the editor, but it wasn't very spontaneous. Some games which had proper MT32 support actually uploaded a few custom sounds into the MT-32, for example 'Red Baron' which uploaded the custom sounds of a doppler-shifted aero engine and the clatter of a machine gun which played over the tune during the loading screens.

I'm just wondering if anyone ever came up with some way to make the parameter memory in the stock MT-32 non-volatile so that it would retain all patches and settings during power down? I still have my MT-32.

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Re: Roland MT32 (original) memory retention?

Postby Miguel » Tue Jul 11, 2017 12:47 am

Although these days best know for the Devilfish mods to the TB-303 Robin Whittle of Real World Interfaces used to modify the MT32 including adding a battery to retain it's settings. Robin installed the additional RAM in my old Atari STFM back in the day but alas I always rocked a D-110 so unfortunately I can't help you out with the details.

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Re: Roland MT32 (original) memory retention?

Postby krupkaj » Tue Jul 11, 2017 9:55 am

There is a page with description of battery backup mod
http://www.oldcrows.net/~patchell/mt32/mt32.html

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Re: Roland MT32 (original) memory retention?

Postby siriushardware » Tue Jul 11, 2017 6:45 pm

Miguel, krupkaj, thanks for the responses. I looked at the link krupkaj posted and although there's good information there, parts of the article are dead, notably the images. It's enough to know that the hardware side is basically the addition of a DS1210 RAM battery backup manager IC.

I had not anticipated, although it was obvious once mentioned, that the original firmware would re-initialise the RAM contents every time the unit started up (if it did not, the RAM would be full of random garbage). So on its own, providing battery back up to the RAM would preserve the user modified content for as long as you might like while the unit was powered down, but the moment it was started up again it would wipe the RAM clean :-(.

That's what the modified firmware is obviously for, it has had the RAM initialisation removed. Interesting, thank you.

I'm wondering if it would now be possible to use direct replacement non-volatile battery backed RAMs, like the thick bodied Dallas type which incorporate an integral battery. The firmware would still have to be changed for the same reason as before.

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Re: Roland MT32 (original) memory retention?

Postby crashman » Tue Jul 11, 2017 7:05 pm

Not really dead...
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Re: Roland MT32 (original) memory retention?

Postby charles » Tue Jul 11, 2017 10:06 pm

I think its the sram you need to keep alive , most keyboards used to have a cartridge to store patches on ..
I love the l/a synthesis employed by the mt32 d10/20/50/70 mc303 and ds330
why doesn't the mt32 keep its memory ...cant the sysex write to the timbre or temp voice and then save to memory ....
I know ther eis a hack where you piggy back the ram and make a board to hold a coin cell cr2032 which once machine powers off it holds your voice data and rereads upon reboot
maybe it doesn't call ram on boot ?????
have you looked to see if there is a os upgrade to use user made voices?
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Re: Roland MT32 (original) memory retention?

Postby siriushardware » Tue Jul 11, 2017 10:37 pm

Crashman, thanks for finding those files, appreciated.

Charles, the MT32 was the entry-level model in the series and as far as I know it copied all its voices from ROM into RAM at start-up.

Using editor software you could alter the RAM copies of the original voices or just make completely new ones but they were still in volatile RAM and would be lost when the unit was powered off, so the only official way to make, keep and re-use your custom voices was to use editor software to extract the edited voices from the unit via sysex, save them, and then upload them back into the unit again at the beginning of the next session. It was possible to automate this process by having a patch uploader as a desktop accessory, so that whenever the ST was started up the first thing it would do was upload the custom patch file into the MT32. But this was cumbersome and meant that you always had to have the ST on hand. You couldn't just connect a MIDI keyboard straight to the MT32 and start playing with your custom sounds.

As designed, the MT32 had no non-volatile storage for user edited settings and parameters, so there's no semi-permanent memory into which the temporary 'working' RAM copy of a patch can be copied. The only way patch data can be saved on a stock MT32 is by extracting it and saving it to somewhere else before turning the unit off. Hence the interest in this RAM backup modification.

It strikes me that the modified firmware would need to have a way to force initialisation when required. For example the very first time after this backup battery mod and revised firmware was installed the RAM would not be initialised and would contain random garbage. The ideal starting point would be for all the original voices to be loaded into the battery backed RAM just once, and thereafter retained by the backup battery until they are intentionally altered by the user.

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Re: Roland MT32 (original) memory retention?

Postby charles » Tue Jul 11, 2017 11:26 pm

like a latch so it would boot up then switch over to user ram ....,,ill look into this further
ive been a midi maniac since 1995.....always had a d110 and a dx7
I write software for midi application and the Atari st
and have made a few good colleguezs over the years ,some who love firmware/ram/rom mods

if you wish pm me your email we can talk on there////
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Re: Roland MT32 (original) memory retention?

Postby charles » Tue Jul 11, 2017 11:36 pm

on this page it says the mt32 has 128 rom and 64 ram
???????
need a manual I suspect to decipher this discovery
http://www.polynominal.com/roland-mt-32/index.html
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Re: Roland MT32 (original) memory retention?

Postby siriushardware » Wed Jul 12, 2017 6:23 pm

Without knowing whether it is really the case my educated guess would be that half of the ROM contains the firmware and most of the other half contains the default patches which are copied from ROM into RAM at initialisation. Some of the RAM will also be used as working memory area by the firmware.

The voices are copied into RAM so that they can be edited / changed, but of course they cannot be copied from there back into ROM, which is... Read Only Memory.

charles wrote:like a latch so it would boot up then switch over to user ram ....,,ill look into this further


If I had modified the firmware so that it did not normally overrwrite the RAM contents with the default voices at power-on, I would also have made it so that the unit could be forced to do so, perhaps by holding down one or more of the front panel buttons at power-on.

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Re: Roland MT32 (original) memory retention?

Postby charles » Wed Jul 12, 2017 6:57 pm

rewrite a gal/pal/eprom to do so ,,this is a great feat.
lol talk to you in a year or so ...
critical thinking takes time.
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Re: Roland MT32 (original) memory retention?

Postby siriushardware » Wed Jul 12, 2017 7:35 pm

Did you realise that the modification which was discussed earlier includes a replacement set of firmware which, unlike the original firmware, does not copy the default sounds into RAM every time the unit starts? So that part of the job is already done.

The hardware part of the modification provides battery retention of the RAM contents while the unit is turned off.

The firmware part of the modification stops the MT-32 from overwriting the backed-up RAM with the default voices when it starts up.

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Re: Roland MT32 (original) memory retention?

Postby charles » Wed Jul 12, 2017 7:56 pm

no sorry I didn't ...someone has beat me to it ,, but are these chips still in circulation or is there new micro devices
which should be the new suffice?
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Re: Roland MT32 (original) memory retention?

Postby siriushardware » Wed Jul 12, 2017 10:39 pm

Crashman's post contains all the necessary ingredients including, in MT32.zip, the .bin files of the code contents for the two firmware EPROMs.

The replacement firmware ICs would appear to be 27C256 eproms, which should still be quite easily available. However that makes for a total of 2 * 32K, or only 64K of ROM, so that doesn't really square with your finding that the unit is supposed to have 128K of ROM.

You (or someone friendly near to you) would need an EPROM programmer which could program these devices and, if the replacements were 'pulls' from other equipment then they might need to be erased first with a UV light eraser.

I don't know if the modification could nowadays be simplified by removing the original 4 * RAM ICs and arranging for just one large modern SRAM like a 62512 to take their place. This would have the advantage of needing only one DS1210, instead of one for each of the four RAMs. The original four separate _CE signals would have to be combined into one single _CE and passed through the DS1210 on the way to the single SRAM chip. For this to work the way I'm visualising it the unit's memory will need to be byte-wide. If it uses a 16-bit chip things get a little more complicated.

Mounting the new SRAM on the 'daughter' board along with the DS1210 and battery would mean that you would not have to cut any tracks on the MT32 mainboard. If you kept the original RAMs somewhere safe it would be possible to completely restore the unit to its original unmodified condition if ever you wanted to move it on.

Does anyone know if the original firmware devices are ROMs or EPROMs? If they are EPROMs I may just have to dig out the MT-32 just to back up and refresh the firmware, even if I don't do anything else to it. Edit: I think I have the answer to my own question: From the motherboard picture on the site Charles linked to, the original firmware appears to be in Roland-badged ROMs.

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Re: Roland MT32 (original) memory retention?

Postby charles » Wed Jul 12, 2017 10:54 pm

there were two version aparentily of the mt32 had to mention
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Re: Roland MT32 (original) memory retention?

Postby siriushardware » Wed Jul 12, 2017 11:04 pm

Yes, not sure what the differences were yet. No idea which one mine is. While looking at the mainboard picture I noticed another Roland badged chip with a very similar (but not the same) 'HN62...' number, bottom left. Maybe this is the ROM which contains the voice data which is loaded into the RAM on startup. The other two ROMs, next to the RAMs, will probably contain program code / firmware only.


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