Does anyone know anything about this? I recently picked up a Roland Realtime Arranger RA-90, which appears to be a very early device with a GS sound source inside - so early in fact, I think this is one of those devices that refers to GS as 'GS Standard'. This device is from early '91, so around the launch of the SC-55. The RA-90 ROM is dated May '91. The RA-90 seems a bit of an oddball device as it was made by Roland Italy, and it shows. The board designs, the physical design, and the typeface used on the device - it all feels a tad 'off'.

You can hold MIDI SELECT during power-up to put the device into 'GS Standard Mode' - basically, it'll bypass all arranger functions and turn into a GS synth module. It doesn’t respond to a GM reset which confims the early nature of it.

The device has a 'GSE board' inside which contains the GSS1 chipset. The board also has a 'GSS technology' silkscreen, which presumably refers to GS Standard. I assume GSE is for a GS Expander or GS Expansion.

Anyway, the board itself has all the standard first-gen SC55 stuff; the R15239148 24-voice synth chip, GSS.A, GSS.B, and GSS.C wave ROMs, R15239147 gate array, NEC UPD6376 DAC, etc. The only oddity is that the CPU is labelled as GSS1; it's still an H8/532 with built in ROM; there's even a footprint on the board for a full size version too. I still need to dump the control ROM, which is 2Mbit.

As for the I/O on the board, it has a built in analog audio section, separate line out and headphone out connections, a volume control connection, and a single connector that provides +5 and +9 volt feeds, as well as MIDI RX and TX.

The board states that it was designed for the RA-90, E-35, and E-70 devices; I just wonder if it took off elsewhere? I know Roland used the RLP-3037 board in other devices which appears to have a 'GSS2' labelled CPU - as to how it's different though I've no idea.

Anyway, thought this information may be of some interest to someone!