Try swapping both a and b drives. Try with only 5 1/4" plugged in to a and then again to b. Makes a difference? Specify make and model of motherboard, drives. Describe cable. Describe ROM settings. Bill Degnan twitter: billdeg vintagecomputer.net I have connected a 1.2M 5.25" floppy to my computer. After a bit of jumper learning and setting, it's recognized and reads my old DD and HD floppies fine. But for the life of me I cannot write to it. Not under DOS, Win98, or WindowsXP. Which all read fine. But can't add a file. It goes through to the motions and makes the noise, heads moves as if everything went fine, but if I take the disk out and put it back in, the file is not there. I can't format either. Fails after a while on the above OS'es with different error messages without the head moving past track 0, suggesting it can't even read back the first track it's trying to format. Formatting from ImageDisk or OmniDisk looks like it works (head goes through the motions over the whole disk). But nothing seems to be written on the disk: neither utility can read the formatting back. Both HD and DD. On the same cable there is a 3.5" A: drive which reads and writes fine. Can't be the controller since it works on the 3.5" drive? The cable maybe? I tried several. Anyone has had this happened ever? Time to bring out the o'scope?

Date: Tue, 18 Aug 2015 21:30:31 -0700 From: cclist at sydex.com To: cctalk at classiccmp.org Subject: Re: 5.25 floppies that read but don't write On 08/18/2015 09:05 PM, Marc Verdiell wrote: Make sure that "WRITE GATE" goes low (use a logic probe) on pin 24 of the drive while you do your write. If so, your floppy write circuitry has a problem. I.e., it's not the cable. --Chuck

We also had some fun when the purchasing department gave us HD disks! (for use in TRS80 model 1 SD) They would sometimes FORMAT, WRITE, READ, and then minutes later, be blank again. The purchasing agent was in bed with somebody peddling RoyType, and kept substituting those for whatever we ordered.