Casio CFX-9850GB Plus 32KB WE (White Edition): 64KByte "upgrade" reconfiguration

[jebem]

(11-23-2016 04:16 PM)Mark Wrote:  (...) the CFX-9970GT seems to be mostly identical from a software point of view. I just did another self-test on my 9990GT.

It will be interesting, shall I eventually succeed in configuring my machine for 128K, to check if the test actually runs through the whole 128K space.

On the hardware side, I remember that it doesn't look the same as the CFX-9850GB, it is more complex : 6 LSI chips versus 4. I only opened it for a few minutes to check for corrosion, the day I got it for a few bucks. I suppose that the 9850 is a more integrated iteration of the same architecture...

I have opened my CFX-9970G and yes, the mainboard has 6 chips but also have one additional chip in a module inserted in a slot on the other side.

1) Chip in a module inserted in the slot:
8 Mbit PROM module, using a NEC µPD23C8000XGX.
Accordingly to the IC manufacturer, it can be configure as 1M 8-bit words, or 512K 16-bit words.

This module have configuration jumpers (zero Ohm resistors).
Default setup:
R402 - Open
R403 - Closed
R404 - Open
R405 - Closed

Probably it can be possible to configure the operating system firmware to enable above the factory default of 64KByte of SRAM, by changing the above setup. More information needed and/or additional time to do testing.

2. Chips in the mainboard:
- LSI101: unidentified IC
- LSI102: NEC µPD23C4001E 4Mbit with 512K 8-bit words PROM.
- LSI103: SANYO LC3564SM 64KByte SRAM.
- LSI104: unidentified IC.
- LSI105: CASIO F3660-ZD - Can't find information
- LSI106: EPSON SRM20V100LLMX7 128KByte SRAM.

The PROM chips are correctly listed in the sef test.
Interestingly, there are two SRAM chips, one of 64KByte and another with 128KByte.

I don't have the service guide and do not time now to investigate as I have a business trip coming and need to prepare my work.
If you have it, p,ease let me know.

The photos are published at my blog here, as well as the links to the chips datasheets and catalogs.

Thanks.
Cheers,
Jose