Hi I thought I'd update my progress. I'd modified the board that was intended to run 8 inch disk. I had the binary for the EPROM that ran the 8 inch drive. The board required a crystal change, capacitor change in the PLL and one capacitor in a oneshot. I decompiled the code for the 8 inch disk and found the read needed commands and setup to get it to read the disk. One the 5.25 disk, it justt wasn't working. I wasn't sure what the problem was so I brought out the scope to see if I could look at the data going into the USART. At first I thought it might be a problem of the 5.25s using using a different sync byte. I connected the scope up and wouldn't you know it, the delayed sweep scales I needed to see the first few bits wasn't working correctly. I had to debug the scope first. This took some time because like most scopes, the circuits are hard to access ( unlike older Tek scopes ). It turned out to be a CD4001 IC that wasn't working correctly. Now back to the controller. With the delayed sweep I could now look at the bits entering the USART. It was seeing the same sync bytes as used in the 8 inch drive but I still couldn't read a sector. Of course the calaculations for a 32 sectored hard drive would be different than a 10 sectored 5.25. Still I should be able to read something on the first track. It took me some time to figure it out but I believe I know the problems. The reason I couldn't read any data is that the 8 inch has sync, sync, track, track\, sector, sector\, data, crc. It seems the 5.25 has sync, sync, sector, sector\, track, track\, data, crc. Now I need to blow a new EPROM to fix this. I also need to change how the tracks are calculated. For this, I need a little help. Since the 8 inch drives were 32 sectored, calculating tracks from a disk offset number was easy. 5.25 disk with 10 sectored will require something different. Is there an easy way to to separate track from sector using Z80 code? Dwight _________________________________________________________________ Climb to the top of the charts!? Play the word scramble challenge with star power. http://club.live.com/star_shuffle.aspx?icid=starshuffle_wlmailtextlink_jan