What is the right way to search for FM-Pak and its RAM?

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By gdx

Enlighted (4833)

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04-10-2021, 10:45

No need to search the SRAM because it is in the same slot of the MSX-Music ROM.
The standard detection is describe in the wiki:
https://www.msx.org/wiki/MSX-MUSIC_programming#Detecting

As for the simplified clones without ROM, they use the I/O ports only for sound so no need to know the slot. There is no SRAM either.

By Grauw

Ascended (10181)

Grauw's picture

04-10-2021, 10:56

gdx wrote:

As for the simplified clones without ROM, they use the I/O ports only for sound so no need to know the slot. There is no SRAM either.

All MSX-MUSIC clones and internal MSX-MUSIC do have a ROM, and you need detection to know whether to send data to the I/O ports.

For software there’s no point in ignoring good practice and writing blindly, since they need detection anyway in order to enable the FM-PAC I/O.

By st1mpy

Paladin (838)

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04-10-2021, 10:52

Pac doesn't have a rom, so in order to keep whatever game compatible with both pac and fm-pac, the detection of s-ram can't rely on where the fm-pac rom is? (Then there's the other issue about some msx's internal fm rom but that's a different issue).

By gdx

Enlighted (4833)

gdx's picture

04-10-2021, 11:04

Grauw wrote:

All MSX-MUSIC clones and internal MSX-MUSIC do have a ROM

The circuit diagrams I saw had no ROM but if there was one, what would it be used for without SRAM and register access via addresses?

Grauw wrote:

you need detection to know whether to send data to the I/O ports.

No, except instrument data in ROM if there is any.

Edit: Anyway SRAM is not part of MSX-Music. Only FM-PAC & PAC cartridges.

By sdsnatcher73

Prophet (2367)

sdsnatcher73's picture

04-10-2021, 11:15

Well the real question here is how to detect where PAC S-RAM is. It has nothing to do with MSX-Music or FM part of the FM-PAC. Probably only way to find out is by reverse engineering from the old games. My guess would be to look at how Ashguine 2 and 3 did it. They support SRAM and were published by Panasoft so hopefully they have a sort of reference implementation that Panasoft supplied to T&E Soft and MicroCabin.

By Grauw

Ascended (10181)

Grauw's picture

04-10-2021, 12:32

gdx wrote:
Grauw wrote:

All MSX-MUSIC clones and internal MSX-MUSIC do have a ROM

The circuit diagrams I saw had no ROM but if there was one, what would it be used for without SRAM and register access via addresses?

FM-BASIC, FM-BIOS and firmware. I assure you every MSX-MUSIC clone has a ROM. The clones do not have memory-mapped I/O though. Though I do think a real FM-PAC clone including that would be nice.

gdx wrote:
Grauw wrote:

you need detection to know whether to send data to the I/O ports.

No, except instrument data in ROM if there is any.

If you do not detect then you won’t be able to enable the FM-PAC I/O and your program won’t work on FM-PAC. Also you won’t be able to access the FM-BIOS which a lot of commercial games do. And lastly you won’t be able to execute the proper procedure to prefer internal MSX-MUSIC over FM-PAC (as described on the wiki page), keeping the latter disabled to avoid both playing at the same time.

By gdx

Enlighted (4833)

gdx's picture

04-10-2021, 13:36

Grauw wrote:

FM-BASIC, FM-BIOS and firmware. I assure you every MSX-MUSIC clone has a ROM.

I have looked at a few photos and the majority appear to have a ROM indeed. It must have been the early versions that didn't have one. I'm sure I saw some a long time ago. FM-Basic did not work, but all other FM games did.

Grauw wrote:

If you do not detect then you won’t be able to enable the FM-PAC I/O and your program won’t work on FM-PAC.

I know this is not a good idea and yet I have seen it.

By Grauw

Ascended (10181)

Grauw's picture

04-10-2021, 13:32

gdx wrote:
Grauw wrote:

FM-BASIC, FM-BIOS and firmware. I assure you every MSX-MUSIC clone has a ROM.

I have looked at a few photos and the majority appear to have a ROM indeed. It must have been the early versions that didn't have one. I'm sure I saw some a long time ago. FM-Basic did not work, but all other FM games did.

At least my old Checkmark FM Stereo PAK and Zemmix Music Box both had a ROM as well. Curious what types did not. I’m also pretty sure many FM games (Japanese commercial releases) used the FM-BIOS, so I don’t know how they would work without.

By sd_snatcher

Prophet (3486)

sd_snatcher's picture

04-10-2021, 23:29

It's not possible to build a functional MSX-Music cartridge without the ROM. The YM2413 chip is write-only, and this is why the procedure to detect an MSX-Music cartridge is based on looking for the ROM signature on the slots.

A theoretical YM2413 cartridge without ROM just wouldn't be detected by any existing MSX software and would be useless.

By st1mpy

Paladin (838)

st1mpy's picture

05-10-2021, 00:21

If you have a ym2413 cartridge without ROM, it probably will still work if you insert a fm pac (or the machine has a fm), the io will still drive the ym. I did have ym2413 on a breadboard hanging off the cartridge port and it made sounds but the machine had fm too.

There is also one cartridge without the ym2413 but with fm-pac rom, it is the PAC-V cartridge by sharksym. It uses the sram utility program from fm-pac for pac-v sram.

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