DECmate III and Rainbow 100+

From: Ethan Dicks <>
Date: Tue Feb 22 13:36:54 2005

On Tue, 22 Feb 2005 13:01:46 -0500, Paul Koning <> wrote:
> Someone who understands floppies better might be able to deduce the
> correct timing parameters from the description in the PRO Technical
> Manual, but it's above my head.

Here's a table from a posting I made to Usenet in 1990...

"GAP 1" GAP 1: 47 x 0x4E

                SYNCH: 8 x 0x00
                IDAM: 3 x 0xA1
                                1 x 0xFE
                TRACK: (physical track address)
                SIDE: (physical side number)
                SECTR: (physical sector number)

[Repeat once SIZE: 1 x 0x02 (512 bytes per sector)
 per sector ] 2 CRC: 2 CRC bytes

                GAP 2: 22 x 0x4E
                SYNCH: 12 x 0x00
                DAM: 3 x 0xA1
                                1 x 0xFB
                DATA: 512 x 0xE5
                2 CRC: 2 CRC bytes
                GAP 3: 48 x 0x4E

                GAP 4: 6250 minus sum of bytes up to GAP 4 x 0x4E

I wrote the original post in an effort to get someone with Manx to
twiddle a tool for the Amiga (I had Lattice C and the embedded
assembler stuff was entirely incompatible). I do not recall what
document I got it from, but those numbers are from DEC describing the
byte-level format of an RX50 track. Perhaps that would be helpful in
determining timing specifics, especially as they deviate from what PCs
traditionally use.

Received on Tue Feb 22 2005 - 13:36:54 GMT

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