21 Sep
2021
21 Sep
'21
10:07 a.m.
On Tue, Sep 21, 2021 at 9:00 AM Jonathan Stone via cctalk
<cctalk at 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.