26 Nov
2008
26 Nov
'08
1:35 a.m.
micheladam at theedge.ca wrote:
Does anyone know of a 'bridge' converter that
would allow a scsi disk to interface to an MFM controller?
Michel Adam
I'm not sure how that would work. Do you mean replacing an existing MFM
disk with a SCSI disk?
MFM basically presents a signal from the disk heads to the controller
board. It's up to the disk controller on the MFM controller board to do
all the data slicing, bit decoding and so on, and eventually turn the
signal from the disk into a stream of bytes presented to the host CPU.
Modern SCSI disks basically do all that for you - you send it a command
("Give me sector 136") and it returns with a bunch of bytes from that
sector. IDE is practically the same, with a simpler protocol and
simpler physical interface (PATA is just a fast parallel port, and it
doesn't really *need* to be fast. You can hook an IDE disk to *anything*).
Old SCSI disks used to have an MFM or RLL drive with a controller board
that had all the clever stuff on it. On most drive built in the last 20
years, it's all on the drive PCB.
There's not really a way to get the MFM signal back from the data
presented on the SCSI connector.
Gordon