So, how Roland CM-300 is supposed to work - where on the boards are the ROM chips located - nowhere to be found?!
I don't understand, because I see no any ROMs on the pictures of what is inside Roland CM-300:
yet it has the exact same add-on (daughter) board as CM-500:
and here is the CM-500 one:
but with the very big difference on CM-500 main board the Control ROM and the SoundBank ROM are obvious:
mattw wrote on 2023-10-18, 02:07:So, how Roland CM-300 is supposed to work - where on the boards are the ROM chips located - nowhere to be found?!
The discrete GS program and wave ROMs are on the opposite, unphotographed side of the RLP daughterboard. The CPU (IC6) contains its own ROM.
Cloudschatze wrote on 2023-10-18, 03:25:The discrete GS program and wave ROMs are on the opposite, unphotographed side of the RLP daughterboard.
thank you! so, it's all on the other side of "RLP-3037".
Cloudschatze wrote on 2023-10-18, 03:25:The discrete GS program and wave ROMs are on the opposite, unphotographed side of the RLP daughterboard.
just to say - you're 100% right - I got my hands on a CM-300 unit and desolder the RLP board to see its other side. what was the surprise is that the RLP board was not "RLP-3037" (as on the pictures I took from Internet and posted in my initial post), but "RLP-3170".
So, it seems earlier CM-300 units (from 1991) were using "RLP-3037" with V2 GS Control ROM (I am assuming that based on earliest SCC-1 card, as I've never seen the other side of "RLP-3037") and later (1992) units are using "RLP-3170" with V3 GS Control ROM (that is confirmed based on the "RLP-3170" board that I took out).
Now, it's another story what is the actual difference between V2 and V3 GS Control ROM and if it really makes any difference for the end-user. Now, V4 GS Control ROM is SC55mkII and that is essentially no longer SC55, but V2 and V3 GS Control ROM, maybe are 100% SC55 compatible.
P.S. those V2, V3, V4 are not the actual version that is reported in software by the firmware, but what is written as markings on the chip itself.
[EDIT] BTW, those "RLP-3037" and "RLP-3170" boards look like good target for custom solutions, because I guess their pins are MIDI In/Out, Power and I2S signals, i.e. good target for example to take them out and build your own device with better DAC or SPDIF output.
mattw wrote on 2023-11-21, 00:46:P.S. those V2, V3, V4 are not the actual version that is reported in software by the firmware, but what is written as markings on the chip itself.
[EDIT] BTW, those "RLP-3037" and "RLP-3170"
ok, I made dump of the V3 chip on that "RLP-3170" board and found V2 chip dump online - the difference between the two is less than 500 bytes (of 262144 bytes). so, I would say those look like legit "bug fixes" and even probably, because of that "RLP-3170" is actually better SC55-compatible board than "RLP-3037" - unless someone didn't use some of the bugs for special purposes like there are such cases with MT-32.
Further more the firmware version in those 2 chips are:
V2: GS Standard VER=1.10
V3: GS Standard VER=1.20
and for example SC55mkII-compatible Control ROMs have:
GS-28 VER=2.01
i.e. GS with 28-voices polyphony. So, yeah, "RLP-3170" looks like SC55 and not SC55mkII.
mattw wrote on 2023-10-18, 02:07:roland_cm-500_daughter_pcb.jpg
roland_cm-500_roms.jpg
Thank you for choosing photos from my blog https://www.dearhoney.idv.tw/museum/midi-zone … /roland-cm-500/
