Also, it's not a complete SCSI implementation. Some of the commands are different, and it's not processing CDBs.
Technically this is a reverse SAT, converting ATA commands to SCSI commands and then interpreting them, but still, an ST-412 controller doing all this on a stock 8051 in 1988.
It certainly explains why this firmware is so weird...
And some of its support functions are clearly returning ASCs as well. God damn, Everex, you put a SAT in here?
GEE THAT SURE LOOKS LIKE "TEST UNIT READY" TO ME
So I look at what's in the jump table for opcode 0x00, and sure enough:
One of the functions in here converts what for all the world look like SASI error codes or SCSI ASCs to ATA error bits. I'm thinking at this point, "You know, it'd make sense if the translation goes both ways...it'd explain that weird jump table I saw that I couldn't explain the meaning of."
Anyway, basically, if someone has a DTC 5280, 7280, 5278, or 7278 ST-412 controller with the DTC-076 and DTC-114B "huge DIP" chipset and a DTC-378 firmware ROM, I'd love it if someone could dump that ROM and post it someplace.
I'd do it myself if I had one (I have an EPROM burner and basic (de)soldering skills), but I haven't seen one in a good 20 years.
Most things that used a real AIC-010 were either 8051 or 68HC11, but I doubt DTC would go to the trouble of rewriting their firmware for a completely different architecture.
As for the microcontroller itself, I haven't the foggiest. The really old DTC boards used an 8085 and a bunch of standard Intel peripherals (some of which, like the 8254, 8237 and 8259, were also used in PCs), but the 5280/7280 version could be anything.
The third chip with the crystal on it (or the "CR BOX" module on some models) is the sync VFO.
Looking at it again, though, the topology seems like it's textbook AIC-010: One of the huge DIPs is clearly the microcontroller, one is the AIC-010 equivalent where the formatter and its WCS live along with with the CRC/ECC engine, and the third chip is an SSI-ish MFM or 2,7 RLL endec (depending on whether you have a 5280 or a 7280) with WAM/AMD, WPC and data sync support.
I know IBM Japan later had an important role in designing the ThinkPad, so it's possible.
The main chips in the chipset are all Epson gate arrays, many of the other support chips are NEC or Panasonic, and so I'm wondering if IBM Japan or Epson themselves designed this, and not IBM ESD/IBM PC Co.
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