Sigma unidentified flying board

[Michael Sokolov]

   Dear Tim,
   
   You write:
> Any chance it's a simple parallel I/O?
>
> Could also be the bus interface for a Sigma and/or DSD MFM drive
> controller (if so, it probably emulates RL02's).  The assembly number
> sounds vaguely DSD-like.
   
   From looking at the board I see that the BDMGI and BDMGO fingers are
simply shorted and not connected to any circuitry. This means that the
board is non-DMA, right? If so, it can't emulate RL-11 or any other DEC
disk controller because they are all DMA, right? The BIAKI and BIAKO
fingers ARE connected to some circuitry, though, so at least this board
interrupts, right?
   
   And what's DSD? What MFM controller are you referring to? The "SIGMA
INFORMATION SYSTEMS, INC." label and the assembly number are etched, not
silk-screened, stamped, or stickered, so it suggests that Sigma is the
original designer.
   
   Sincerely,
   Michael Sokolov
   Cellular phone: 216-217-2579
   ARPA Internet SMTP mail: msokolov at harrier.Uznet.NET


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