On Tue, Sep 21, 2021 at 9:00 AM Jonathan Stone via cctalk <cctalk@classiccmp.org> wrote: > > One of the reasons I got the 2000s is to format MFM drives for an RQDX3 (I > don't have any PDP-11 CPUs). I have a CMD CQD-420 Qbus SCSi controller, and > an MTI almost-equivalent. I've seen Glen Slick's reverse engineering of the > PLD for the CDQ-200. I hope the newer MTI board "just works"; but if not, MFM > is a fallback.
The MTI QTS-30 board I have is essentially the same thing as a CMD CQD-200 board, just with different firmware. It can be converted into a CQD-200/TM functional equivalent by swapping the firmware EPROMs and CSR decode PAL. I haven't seen an MTI version of the CMD CQD-420 board. The CQD-420 is more similar to the CQD-220A than the CQD-220, with the standard CSR address decoding being done in the QBC0420 ASIC instead of in the PAL. The CQD-220A / CQD-420 PALs only decode the "special" disk/tape CSR address when that is selected via the address selection DIP switches.
