Dec RQDX: What kind of chips on it?

Paul Koning paulkoning at
Mon Jan 4 18:35:20 CST 2021

> On Jan 4, 2021, at 7:04 PM, Warner Losh via cctalk <cctalk at> wrote:
> On Mon, Jan 4, 2021 at 3:40 PM Chris Zach via cctalk <cctalk at>
> wrote:
>> Can someone check to see if a RQDX2 used the Western Digital chips to
>> interface to MFM drives? Reason I'm asking is the MFM emulator can
>> identify an RQDX3, and also a Pro/350 controller but this particular
>> RD52 I have (which was verified by me to run Digital Mumps) is reading as:
>> root at beaglebone:~/mfm# ./mfm_read -a
>> Board revision C detected
>> Found drive at select 3
>> Returning to track 0
>> Drive RPM 3525.4
>> Matches count 36 for controller WD_1006
>> Header CRC: Polynomial 0x1021 length 16 initial value 0xffff
>> Sector length 512
>> Data CRC: Polynomial 0x1021 length 16 initial value 0xffff
>> Interleave mismatch previous entry 0, 9 was 1 now 0
>> Selected head 8 found 0, last good head found 7
>> Read errors trying to determine sector numbering, results may be in error
>> Number of heads 8 number of sectors 18 first sector 0
>> Unable to determine interleave. Interleave value is not required
>> Drive supports buffered seeks (ST412)
>> Disk has recalibrated to track 0
>> Stopping end of disk search due to recalibration
>> Number of cylinders 512, 37.7 MB
> 18 sectors seems odd. The Rainbow had a limit of 16 sectors, but that may
> have been due to other reasons... It had a WD10xx controller.

The Pro also has 16 sectors, that's a limitation of the sector address register.  I know the Pro format is different than the RQDXn format; the latter is larger presumably because of more sectors per track.  So that would fit.


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