J&M/Owl-Ware

J&M disk controller

J&M Systems, LTD. CoCo disk controller cart

Considered one of the best disk controllers for the TRS-80 Color Computers. They have gold connectors and are engineered to a very high standard

Internally has JDOS 1.11 rom on it for fast (6ms) disk drive stepping.

(8/7/12) I've just made a video of this great controller in action on my Coco 3: youtube J&M disk controller for Tandy TRS-80 Coco Color Computer

From: [1]

J&M Disk Controllers for Color Computer
J&M Sytems produced Disk Controllers and complete drive systems including a hard drive system. There were 3 different Controllers, the original JFD-COCO, the JFD-CP and the later JFD-EC. The JFD-COCO was not compatible with a CoCo3, the JFD-EC was introduced for the CoCo3. The JFD-CP features a parallel port to drive a Centronics compatible printer or the J&M hard drive.

JFD-COCO

This was the "classic" J&M controller. It had a 24 pin rom socket, that usually came with a JDOS rom in it. This controller had gold contacts on both ends of the board. Utilized a Synertek SY6591 controller chip, also socketed. This was a good controller till the CoCo3 came out, and it did not work with it. J&M initially recommended changing the 74LS04 to a 7404, but this did not always solve the incompatibility. The final modification was to substitute the Q clock signal in place of the E clock, basically a trace cut and adding a jumper. Simply cut the E clock line (Pad 6). Solder a jumper wire to the Q clock (Pad 7) and connect it to the controller. I used a through hole beside U17 to make the connection on one controller I modified. The controller will now work with the CoCo3 and the CoCo2. If you have a 24 pin JDOS rom, it will also not work with the CoCo3, swap in a RS DOS 1.1 or something such as ADOS 3. See Rainbow, May '87, page 174 for more information.

JFD-CP

This was the second and most deluxe controller that J&M built for the CoCo. Externally it appears different than the original as there is now a toggle switch to select which rom to use, and a header connector which is the built in parallel port. The Hard Drive unit to connect to this controller was originally a 5 Mb Seagate, enclosed in a self contained drive/power unit with built in interface that connected directly to the Centronics compatible printer port. Software to drive it was OS-9 only.

jfd-cp

JFD-CP Parallel Port

PIN  FUNCTION            SOURCE 

1      Write Strobe      Controller 

3      D0                Bi-directional 

5      D1                     " 

7      D2                     " 

9      D3                     " 

11    D4                      " 

13    D5                      " 

15    D6                      " 

17    D7                      " 

19    Read Strobe       Controller 

21    Busy              External Device 

23    N/C 

25    Status            External Device 

26    Reset             Controller

All even pins 2-24 are ground

This connector will allow most Centronics compatible printers to operate with the JFD-CP using a standard, unmodified Radio Shack Model 100 printer cable.

Pinout from page B-3, JDOS Disk Basic Reference Manual, J&M Systems

JFD-EC

The EC stands for economy. This controller was brought out to get J&M back into the lower cost segment of the disk controller market. This controller has a toggle switch to select one of the dual roms, and now supports a 16K device. Cost savings were obtained by eliminating the parallel port , and utilizing the SY6591 controller chip, which J&M apparently bought the entire inventory of when Synertek went out of business.

Thanks to Alan Stallings, formerly of J&M, for correcting some errors and providing more information.

Page last updated Dec 24/2001