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...
C
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
http://www.bitsavers.org/pdf/dilog/2120-0137-1_DQ686_Nov89.pdf
Emulex QD21
http://www.bitsavers.org/pdf/emulex/QD2151002-J_QD21_Jun90.pdf
Sigma SCD-RQD11-EC (There seems to be multiple versions from different
vendors of this same basic board).
http://www.bitsavers.org/pdf/sigmaInformationSystems/400740-B_SDC-RQD11-EC_Disk_Ctrl_Man_Jul88.pdf
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
<cctech@classiccmp.org> 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.
Doug
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
DMA?
