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MFM hard drives, and the RQDX2

Christoffer

Experienced Member
Joined
Oct 15, 2014
Messages
299
Location
Denmark
Hey again!

I'm still on my quest to get my 11/23+ to a point further than "hello world", and after buying a, seemingly functioning, RQDX2 card some months ago, I've been working on/off on avitech.com's RQDX breakout board, for getting 3½'' floppy drives working - at the moment I have no storage on the machine, and that limits the use a fair bit.

Here's the issue: The rqdx boards should also support MFM harddrives, but according to the avitech.com article, only some. Is there any way of telling which ones? I've found one on the local craigslist-equivalent, "NEC, 21 Mb 40 ms". Other places in the ad he's put 21 Gb, but I guess that's a modern habit, it seems unrealistic for am MFM, but I don't know.

Would it be worth picking up? Does anyone has any experience with getting non-DEC MFM's working?
It's the first I've seen in Denmark, and given the weight, it might be expensive to buy further away.
 

Doug G

Veteran Member
Joined
Jun 16, 2012
Messages
541
Location
SoCal
Back then our company built 11/73 based systems. Among others, we used a lot of Micropolis 40/80mb disks, using a non-DEC controller. MTI sticks in my mind as the controller vendor. We also used an unusual operating system, DSM3. We built a couple hundred such systems with good results. Best I can recall the controller supported a standard ST-506 interrface to the disk.
 

Lou - N2MIY

Veteran Member
Joined
Apr 1, 2008
Messages
1,306
Location
Albuquerque NM / Potomac MD
RQDX2 supports the RD51 and RD52. David's MFM emulator works fantastic, I have used it and you should consider buying one from him. Malcolm's RQDX breakout board is also super useful.

I highly suggest that you spring for an RQDX3. Then you can use any MFM drive if you use my procedure for patching the ZRQCH0 formatter. It has been discussed here in another thread. If you send me a PM with your proper e-mail address, I will send you that procedure.

Lou
 

Christoffer

Experienced Member
Joined
Oct 15, 2014
Messages
299
Location
Denmark
Thanks for the replies!

I know the RQDX3 would widen up the spectrum of devices significantly, but they're also usually a tad pricey-er. I'm really not into buying huge amounts of new hardware, I'd like to see what could be possible with what I already own, and I'd originally bought the RQDX2 for adding some 3½'' FDD's running, writing off the HDD completely, that said, it'd still be nice to have.

I'm not that keen on emulating, I can already emulate TU58 tapes and paper tape, and I still think emulating with a modern pc makes using vintage computers massively unsatisfying.

I don't know how standard the RD51 and 52 are, but according to the avitech breakout board page, RD53 and 50's are also working with the RQDX2 - and the '53 is larger capacity than what I've found, so I don't know.
 

Christoffer

Experienced Member
Joined
Oct 15, 2014
Messages
299
Location
Denmark
Thanks for the reference, but I'm still unclear on whether completely different MFM drive models might work, or if it's certain that only the DEC ones and equivalent ones does.
 

MattisLind

Veteran Member
Joined
Sep 30, 2013
Messages
898
Location
Stockholm, Sweden
Thanks for the reference, but I'm still unclear on whether completely different MFM drive models might work, or if it's certain that only the DEC ones and equivalent ones does.

Now I cannot find the reference but this what I have gathered: The RQDX1/RQDX2 are quite similar. Probably just firmware differences. The RQDX3 is completely different. The former stores the heads, cyls info in the firmware while the RQDX3 stores this info on the drive. That means that the only way to support a non-standard drive on a RQDX1/2 is to reverse engineer the firmware and change that table. On the RQDX3 it should be a matter of patching the formatting program.

Dealing with the RQDX1/2 firmware might be a fun exercise but since MFM hard drives are end of life in many ways it is probably wise to do as Lou suggest and get David's MFM emulator and use it as a RD53. You get at least 70 megs of reliable hard drive for you system.
 

MattisLind

Veteran Member
Joined
Sep 30, 2013
Messages
898
Location
Stockholm, Sweden
Unless you already read about it I can confirm that a RQDX1 with upgraded firmware to 10.0D works just fine with a 1024 cylinder 8 head RD53 emulation image on the mfm emulator. It formats well under ZRQBC1.BIN. Works fine under ZRQAH0.BIN exerciser and boots in RT-11. Supposedely it would work equally well using a RQDX2 since the firmware is the same.
 
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