View Full Version : Does anyone have a working Dataspeed Conductor floppy controller?

October 3rd, 2017, 07:33 AM
I acquired a Dataspeed Conductor floppy controller about a month ago in order to install it in my IMSAI with the JAIR 8080 so I could hook up some 8" floppy drives. Fortunately it came with a manual, schematics, and an example BIOS for CP/M 1.4. I've been fighting with it for quite a while though and I feel like I am so *very* close to making it work, but now I've hit a road block that makes me question whether the design ever worked at all!

I had to replace the two missing 74LS51 chips and a tantalum capacitor that blew up because it was installed the wrong way, and modified the board to send the phantom signal since it wants to memory map I/O at 0xF000-0xF0FF and I didn't want to have to give up 8k of RAM. I also verified that the FD1791 in it is good by installing it into my TRS-80 Model II and connecting my 8" drives to it and was able to read/write existing disks and format new disks both in FM and MFM formats. I also used my TL866 to test as many of the 74xx chips on the DS Conductor as I could.

I've modified the JAIR BIOS so that it supports the DS Conductor and when I try to access a floppy drive the head seeks to the correct track and the head loads and it attempts to read data. However no data ever comes in to the RREAD pin on the FD1791. I pulled out the oscilloscope and logic analyzer and I can see data coming from the drive and clock signals are being generated at the right frequencies. But as I trace things through I see they ran the raw data into an LS193 4-bit counter, and then ran the carry output over to the FD1791. The carry output never changes because every 6 to 7 bits of raw data the counter is reset by a 74LS123. This makes no sense to me!

I've scanned the manual and put up here if you want to take a look at it:


Does anyone have a Dataspeed Conductor in their system and have it working?