Hi Dick Sorry for the delay, just had to dig further into this. Brief history, the Molecular came to me dead in more than one area. I got the main processor going with a new Counter timer chip. At that point I could not Read or Write to the hard drives but the Floppy was fine. The WD 1001 SASI to MFM controller was not seeing or interfacing with the drives. The SASI connection seemed ok. I pulled the first hard drive and attached it to a PC. It formatted fine with no errors. HD's are Seagate ST 419 15 meg 5 1/4 Drives. So I replace the cables and looked into the controlled further. Could not find a true cause of the problem with the controller. It seemed to not select the drive, nor the head. I finally gave up and robbed one of my other systems of WD 1000 to try. I did get the Light to come on on the First drive when it booted. I stopped there and Posted a request for a controller in comp.os.cpm. Did not find one and after many months just setting I decided to Give the system an- other try. I tried formatting the drives. It just hung there for ever. I retried this on one of the other drives, still just hung. So I posted to this list. Since I received more that one Email that the other SASI to MFM controllers should work. I went back and looked further. The hanging was due to the fact that the Heads on the the Drives where eating the Platters and the controller just could not format the drive. After putting the Drive back on the PC, the PC Controller had all kinds of errors. I remove the cover and found the disks are bad. All three drives have the same problems. These are 306 cylinder 6 heads. I have about 50 Dives but none with this head and cylinder count. So I don't really know if I really do need the correct controller yet or not. I do need a seagate ST 419 or similar drive though. I still would like a WD 1001 5.5. for 2 reasons. 1 to keep the Molecular original and 2 to help trouble shoot the other controller. For those following this Post. In the earlier days, the SASI interface was used to interface to these controllers which could control up to 4 MFM drives. They came in 2 sizes. One would attach directly to a 5 1/4" drive the other (which I have ) was 7" x 10" and could come set up for controlling either 5 1/4 HD's or 8" hard drives. I don't know what real code differences there are between the controllers. There is a different clock and interface for the 8" hard drives. The chips used and the layout is quit different between the different boards. SASI is the early version of SCSI. It had most of the same signals and has a 50 pin connector. One big difference is what all the pins where used for. The one here has the power and ground for the WD 1001 card supplied though the cable. Others have a separate power connector. For those that though I needed a PC ISA card. I guess they just used the next number in line when the made the WD 1002 xxx ISA bus to MFM controller. What is a Molecular?? It is a Z-80 basic multi user system. It had 1) Z-80 computer that controlled the Disk system and 4 to 10 slave cards that each user was connected to through a dumb terminal. OS is CPM and Nstar. Thanks, again Jerry Jerry Wright JLC inc. g-wright(a)worldnet.att.net Richard Erlacher wrote: