I certinly am.
The upper board in the drive chassis, the oen that hinges
open. It contains a couple of 2901s and some 2911 sequencers IIRC.
(2) 2901's and (3) 2909...
Yes, you';re right. It's been a long time... Many of the 3rd-party Qbus
floppy controlelrs that did an RX02 format on normal SA800 drives used a
pair of 2901s and a 2910
Writing a disassembler for the mcirocode
wasn't hard once I'd understood
the hardware. Thgen figuring out what the code did wasn't that hard
either, I think it took 3 or 4 train jouneys :-)
I find (4) ROM-like substances on the RX02 controller in front of me.
Three are MMI 7643-5 devices which are 1024x4 bipolar PROMs at locations
E67, E60, E48.
One is a TI TBP24S41 which is also a 1024x4 bipolar PROM at location E53.
RX02 print set here,
page 22, shows them all as 7643 type so the TI part is a later substitute
IIRC it's 1K words of microcode. There's no reason to use a particular
manufacturer's ROMs, they all read (although not program) the same way.
E67 is labled "229F1".
E60 is labled "230F1".
E53 is labled "431F1".
E48 is labled "232F1".
These are not socketed so will need to be desoldered and then fed into a
programmer/reader. It looks like my DataIO System 19 will do 24S41/74S476
so I think I can read them there.
I read them without desoldering, but it was a pain. If you look at the
printset, you'll see the OE/ line of the seqeuncers is connected to an
inverter, the input of which is pulled high. So if you pull that input
low, the sequencers outputs are disabled and stop driving the ROM address
pins. So did that, then put a test clip on each ROM i turn, sequenced
the address pins and captured the data.
If I desolder these and read them, do we really have use for the bits?
I really should still have sump of them around here somewhere...