Dec RQDX: What kind of chips on it?

Joshua Rice Rice43 at
Tue Jan 5 05:47:24 CST 2021

I’m not sure where i read it, but i’m pretty sure the main “brains” of the RQDX2 is a T-11 (PDP-11 FALCON) chip, and that does the negotiations between disk and system. I don’t know if it’s the same for the RQDX3, but i’d suspect not, as the incompatabilities between the 2 and 3 are probably due to a controller redesign. Though i really am no expert when it comes to disk controllers, and barely qualify as an amatuer with QBUS PDP-11’s in general!

I have a suspected faulty, but never tested (water damaged) RQDX2 i have pulled from a MicroPDP-11/23 i have been restoring. I don’t know if it’s any use, but i’m sure i can let it go for a pittance as long as you’re located in the UK

> On Jan 4, 2021, at 10:40 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
> Thanks!
> CZ

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