VOGONS


First post, by mattw

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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:

roland_cm300_01.jpg
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Roland CM-300 Inside
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yet it has the exact same add-on (daughter) board as CM-500:

roland_cm300_02.jpg
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Roland CM-300 add-on PCB
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and here is the CM-500 one:

roland_cm-500_daughter_pcb.jpg
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Roland CM-500 add-on PCB
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but with the very big difference on CM-500 main board the Control ROM and the SoundBank ROM are obvious:

roland_cm-500_roms.jpg
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Roland CM-500 main board
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Reply 1 of 4, by Cloudschatze

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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.

Reply 3 of 4, by mattw

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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.

Reply 4 of 4, by mattw

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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.