Good data, thanks! I kind of like the ESDI disks, they're more solid and reliable than the MFM ones, and to be honest the RQDX3 was not a super fast disk controller. I wonder if it could do block mode DMA.

I'll keep an eye out for the Sigma, the only thing I wish I had on the MTI MQD13 would be some disk cache to speed things up. Granted 11/M+ does have disk caching in the OS, I should check to see how much quicker that makes things.

Good used ESDI disks come up on Ebay from time to time. A nice 660mb CDC is enough for most general pdp usage...


On 4/19/2022 1:03 PM, Glen Slick via cctech wrote:
I also have multiple ESDI controllers, more than one these flavors:

Dilog DQ686

Emulex QD21

Sigma SCD-RQD11-EC (There seems to be multiple versions from different
vendors of this same basic board).

They all support block mode DMA transfers, and command queuing with
seek optimization. The Dilog DQ686 and Emulex QD21 are dual wide
boards. The Sigma SCD-RQD11-EC is a quad wide board and has 1MB of
cache memory (which takes up about a quarter of the board area). The
examples I have might only be populated with 512KB of cache memory.

I might have had close to a dozen working full height 5.25-inch ESDI
drives at one point. Unfortunately most of them have failed while
sitting idle over the last few years. Without checking now I don't
know if any of them still work. So the dozen or so Q-Bus ESDI
controllers don't have any use for me now. (Fortunately I also have
more Q-Bus SCSI controllers than backplanes to put them in).

I also have a single Andromeda ESDC ESDI controller. Never found a
manual for that one. Did eventually figure out how to get into the
on-board configuration utility.

On Tue, Apr 19, 2022 at 8:56 AM Douglas Taylor via cctech
<> wrote:

Once upon a time I used an Emulex QD21, but I sold it because the actual
ESDI disks I had were a pain in the butt.  Always crashing.
I still have a Webster (quad board) SRQD something.
I think I had a Dilog board also.  It's been a while, probably 20 years.

On 4/18/2022 9:12 PM, Chris Zach via cctech wrote:
Interesting, what kind of ESDI controllers do you have? They got
advanced features like cache, ordered seeks, and burst mode/block mode

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