Tips on getting the Siemens 100-8 SSDD 8 inch disk drives running with the Morrow DJDMA disk controller. Two problems arise when configuring the 100-8 for the DJDMA. The first is the jumper settings, and the second is the CP/M BIOS drive parameter tables. The DJDMA needs some odd (compared to other controllers) jumper settings, and the 100-8 drive parameters (step rate and settling time) are not always what Siemens' (now World Disk Drives, Irvine, California) documentation would lead one to expect. Jumper Settings The DJDMA requires the following characteristics of its disk drives: 1. Radial (daisy chained) drive select 2. Head load when drive is selected and door is closed 3. In-Use LED on from drive select 4. Stepper power from head load 5. Soft sector 6. Terminating resistors on the last drive in the daisy chain For the 100-8 the approriate jumper settings are: Rad Sel 0 in drive A, 1 in drive B Rad Step 2 12 yes 16 no 18 no 20 yes 22 yes 24 yes 34 yes 36 yes A no B no C no D yes E yes F no G yes H no J no K yes L yes M no RI yes RR yes V no SS yes HS no Term Res. no on drive A, yes on drive B Act LED U no S no R no H yes SE yes TE no BIOS disk parameters The Morrow BIOS comes configured for Shugart 800/801 drives. They require 8 millisecond step and settle times. The Siemens documentation says that the 100-8 needs 3 to 8 milliseconds "access" (by which I think they intended "step") time and 14 milliseconds settling time. I've got the feeling they reversed the numbers. 8 milliseconds was sufficient settling time under all conditions. I tried 8 milliseconds as the step parameter and the operation was erratic. More often than not the drives couldn't keep up with the step rate and would fail the track seek. I then changed the step parameter to 14 milliseconds and all worked fine. I tried reducing the step parameter in 2 millisecond increments and all worked fine down to 10 milliseconds. To be safe, start with 14 milliseconds and if you're adventurous, try reducing it until you start getting slightly erratic seeks. You can tell you've gone too far if, instead of getting a clean head movement directly to the requested track, it tries more than once, returning to track 0 in the process. Back off 2 milliseconds and your drive will be seeking as fast as it can. I don't know if stepping the drive at faster than 14 milliseconds hurts the long term reliability of the drive, so if you're worried about such things, leave it at 14. I used DU-V87.COM (available on many RCPM systems) to help pinpoint the seek problems. It allows you to command the head directly to any track. Len Moskowitz Fair Lawn, N.J. October 1984