View Full Version : MTI MXV50 Floppy controller

July 5th, 2009, 03:05 PM
Hello guys!
It seems that I have stuck with Micro Technology Inc. MXV50 floppy controller. :confused:

I would like to put in life some robot controller based on KDJ11-A QBUS CPU, 512kW memory board, DLV11-J clone, Boot board, some I/O and floppy controller board.
I have ODT access (excellent PDP11GUI, www.j-hoppe.de/pdp11gui.html) and QBUS problems (CPU error 24) with MXV50 board.
One of the buffers connecting ROM with CPU on this board have burned down, but changing with new one did not fix the problem.
Any documentation for this board will help a lot, and some diagnostic software will really push things up.

Do someone could help me to fix this controller? :)

Lou - N2MIY
July 5th, 2009, 03:53 PM

Good luck finding the manual for that controller. You should strongly consider using a real dec RQDX3 (M7555). They come up for sale often on ebay.


July 6th, 2009, 09:41 AM
Thank you Lou,

MXV50 is actualy "MSCP RX50 emulating Floppy (SA612) Controller" working with one 3.5" floppy drive (RX24, I presume). Original documentation know for 5.25" but not for 3.5".
Wierd slightly. :(
Do you realy mean that RQDX3 could be of help? :)


Lou - N2MIY
July 6th, 2009, 04:09 PM

The RQDX3 certainly won't support the RX24, but it will support RX50 and RX33 and best of all (and most importantly), all the documentation is available!

I have found that the availability of documentation for the MTI controllers is sparse. I have an 11/23 with an MTI MXV22 (emulates dec RXV21 when connected to SA800 drives) and an another MTI controller (can't remember the model) that uses an MFM hard disk to emulate a dec RLV21 and two RL02s. I have only been able to ever find the MXV22 manual.

So, when building any system, I find that sticking with dec cards has given me the greatest chances of success (becuse the documentation is usually available.)


July 7th, 2009, 12:12 PM

I agree with you, dec cards are realy better choice. I have what I have and must survive with it :)

It seems that I was pretty successfull today :) !
I am using RT-11 V5.3 now (converted to be bootable from TU58 emulated with PC, RL02 -> DecTape II with driver for using more space than standard 256KB).
Well, now I have chance to test floppy board, floppy drive and floppy disks in normal environment.
SHOW command recognize DU device. Is it enough to count on MXV50 like working?
I will play a little with empty floppy disk trying to format, initialize, copy or what ever in order to check this part of the system.
This morning I started with XXDP TU58 image but it is not obvious which test to use.

Thank you, Lou, for supporting my efforts to put this beast :) in operation.
I appreciate your advices. Regards!


Lou - N2MIY
July 7th, 2009, 03:32 PM

It sounds like you are making fine progress!!! I have done exactly what you did in the past. I found the RL02 RT-11 V5.3 image and made a bootable TU58 image and booted from it with Will Krans' TU58.exe. I also made an XXDP bootable TU58 image. I assume you used Will's program.

There are many XXDP routines you could run to check out your hardware. To format RX33 floppies, one would usually use ZRQC?? (latest I saw was ZRQCH0). However your setup sounds interesting. Do you really think the RX24 will work on that controller? I have never seen 3.5" floppies used with an 11.

Do you have any hard disk controllers? Running off floppy is slow (and TU58 is even slower).

Are you in a country where you can get an RQDX3?


July 8th, 2009, 03:24 AM

Yes Will's TU58EM, PUTR and PDP11IDE (J. Hoppe, Göttingen, www.j-hoppe.de/pdp11gui.html , j_hoppe@t-online.de)

You could see boards and robot mechanics (earlier photo without a lot of details) at http://www.epro-rs.com/news.php?readmore=1
Floppy drive is M2532K-19A Fujitcu (Google: M2532K-19A Floppy Drive 0.72 3.5 3H).

Well, in Serbia is a hard task to find RQDX3.

My task for today (and a few next :) ) is to find out what is wrong in board, drive, floppy chain.
There are E11 MSDOS floppy read utility. According to E11, something is wrong with floppy disks but this depends on PC hardware. I have used another utilities to read floppy disks and I have images now. There one could find the RT11 block structure and from there is idea to boot RT-11 and try floppies directly. Images are peculiar (720KB long) because directory block is shifted 20 sectors from the start. Text is readable.
For now Format command from RT-11 respond with "?FORMAT-F-Device invalid or not supported by FORMAT" and this is logical, because MXV50 is MSCP controler and FORMAT could not do the task (according to RT-11 manual).
On RT11 image is DU.MAC, and I find another two MSCP utilities DUSTAT.MAC and DUTEST.MAC. Today I will test it all :D .


July 8th, 2009, 03:59 PM
Hi Lou,

Here are the tests with Dutest.com

=res ;Reset controller
=ini ;Initialize controller
Returned values: QB DI Step 1 bits 7:0=100 (documented as 000)
Port type = 0, reserved step 3 bits 10:8 = 0, model = 007, FW version = 11
=op gus ;Get unit status
=go ;Execute
=sh r ;Show received

It seems that MXV50 is alive but commands for formating the floppy doesn't work...



Lou - N2MIY
July 8th, 2009, 04:10 PM

That is a very nice robot that you have there! Made in Austria! You are very lucky. I looked at the boards, and this looks like it was always a floppy only system - no hard disks. And yes, the floppies are 3.5"! (I believe you now.)

Since this is an MSCP controller, I assume that the 3.5" floppy drive is DU0: . Can you do DIR DU0: ? When you do SHOW DEVICES, is the DU: handler loaded?

Yes, In RT-11, FORMAT usually doesn't work with MSCP disks. They have to be formatted elsewhere (like with ZRQCH0 for RX33s, or dec RX50s came pre-formatted). To set up the RT-11 filesystem on a formatted MSCP drive, you use INITIALIZE.

I am glad that you made images of those floppies on a PC. They are very precious! Maybe you used something like this program: Imagedisk (http://www.dunfield.com/dave/dsktools.htm , http://www.classiccmp.org/dunfield/img/) It is a DOS program that will allow you to make an image of your floppies. Even if you cannot eventually find a correct formatter that will run on your 11/73, you can make formatted disks on the PC this way.

It is very good that they have RT-11 structure. Have you seen PUTR? (http://www.dbit.com/pub/putr/) With it, you can mount and work with RT-11 filestructures on a PC running dos.

That MXV50 looks like a complicated board. I see the AMD2901 bitslice processor and lots of custom PALs. It may not be easy to troubleshoot, especially without schematics and a technical manual.

If you can send me the image files, I would like to try to mount them with PUTR and try to put them on an RX33 and make it bootable. The RX33 was a high density 5.25" floppy (more than big enough to hold everything on the 720K floppy). I have an 11/73 (see here: http://www.vintage-computer.com/vcforum/album.php?albumid=2&pictureid=228 but the picture is old and I now have RX33s in here instead of the RX50 in the picture).

If I can make a bootable RX33 floppy, then you could replace the broken MXV50 (if it is broken) with an RQDX3 and RX33. RX33 drive is a TEAC FD55GFR floppy drive, very common here in the US.


Lou - N2MIY
July 8th, 2009, 04:14 PM

I just saw your results of DUTEST after making my last post. DUTEST says this drive looks like an RX50.

Please try DIR DU0: to see if you can take a directory of the floppy on the machine (or I hope you have made copies of the floppies so that you are not using the real floppies.)


July 9th, 2009, 09:58 AM
Hi Lou,

I did it but RT-11 respond with "?DIR-F-Error reading directory".
Yes, with SHOW DEV one can see DU: handler.

According to DUTEST, CPU comunicate with MXV50 and send/receive MSCP packets.
It is not possible to use DUTEST Format command, meaning that something from controler outlet to floppy head is rotten. This should be also a good test that floppy chain work.
Now I will find some exerciser for floppy to see is it posible to control flopy mechanics.


July 10th, 2009, 12:46 PM

For some reason I am not able to make xxdp tape with following:
634: ZRQAH0.BIN 1-MAR-89 67 blocks start 14775 end 14841
635: ZRQBC1.BIN 1-MAR-89 20 blocks start 14842 end 14861
636: ZRQCH0.BIN 1-MAR-89 72 blocks start 14862 end 14933
637: ZRQDA0.BIN 1-MAR-89 71 blocks start 14934 end 15004
638: ZRQEC1.BIC 1-MAR-89 77 blocks start 15005 end 15081
639: ZRQFC0.BIC 1-MAR-89 34 blocks start 15082 end 15115
640: ZRQGC0.BIN 1-MAR-89 74 blocks start 15116 end 15189

Could you make a bootable tape image for me with this tests. This will be the great help.
(My copy of putr does not see mounted xxdp tape in normal way like xxdpdir)


P.S. You could see some pictures in my album.

Lou - N2MIY
July 10th, 2009, 05:08 PM

Send me a private message with your proper e-mail address and I will send you the bootable TU58 XXDP image with the diagnostics you are interested in. (And I would gladly do the same for anyone else seeing this thread.) I'll make it tonight or tomorrow morning.

Those are the diagnostics for RQDX1,2 and 3. It will be interesting to see if any of them work with your MXV50.


P.S. in the last photo, it does not look like RT11FB (foreground/background monitor) on the screen. That must be some other FB. :)

July 11th, 2009, 03:08 AM

Right, another FB, Facebook :)