Exerpted from the "CP/M FAQ", available via any Web search. This was exerpted Dec 20th 2006, check the most recent version. - Herb Johnson Q14: Can I read my 8" disks with my PC? A: (John Baker, Tom Sullivan) With a program called 22disk, and an adaptor board that you can make, you can read those disks on your PC. All it takes is rearranging some of the lines on the 34 pin cable, and wiring them to the 50 pin cable, and you're in business. The interface on 8" drives and 5 1/4" drives are essentially the same. The 34 lines on a typical 5 1/4" controller are sufficient to control most 8" disk drives using soft-sectored disks. Here, is a diagram for a basic conversion cable to allow connection of an 8" drive to an IBM-compatible, AT-style (high density) controller. 8" disk drive PC-AT style controller Based on Shugart SA-851 Grnd. Sig. Sig. Name Sig Name Sig Grnd 1 2 Double/High Density ->> >>- Write Current Switch/ 2 1 Active Read Compensation User Customizable I/O pins 4 3 " " " " 6 5 33 34 **Ready ---------------<<------------ True Ready 8 7 <<-------------#Two Sided 10 9 33 34 **Disk Change ---------<<----------- Disk Change 12 11 31 32 Side 1 Select ------->>-----------#Side Select 14 13 3 4 In Use/Open --------->>---------------- In Use 16 15 15 16 *Motor On ------------>>------------- Head Load 18 17 7 8 Index ---------------<<----------------- Index 20 19 33 34 **Ready ---------------<<----------------- Ready 22 21 <<---------------##Sector 24 23 9 10 Drive Select 0 ------>>-------- Drive Select 1 26 25 11 12 Drive Select 1 ------>>-------- Drive Select 2 28 27 13 14 Drive Select 2 ------>>-------- Drive Select 3 30 29 5 6 Drive Select 3 ------>>-------- Drive Select 4 32 31 17 18 Direction Select ---->>------ Direction Select 34 33 19 20 Step ---------------->>------------------ Step 36 35 21 22 Write Data ---------->>------------ Write Data 38 37 23 24 Write Gate ---------->>------------ Write Gate 40 39 25 26 Track 00 ------------<<-------------- Track 00 42 41 27 28 Write Protect -------<<--------- Write Protect 44 43 29 30 Read Data -----------<<------------- Read Data 46 45 <<------##Separation Data 48 47 <<-----##Separation Clock 50 49 This diagram also works in the other direction--that is, to attach high-density 5 1/4" drives to an 8" controller. Notes: * - It seems to be a logical substitution since the vast majority of 8" drives have continuously running spindles and instead of MOTOR ON require a HEAD LOAD signal. Also, a controller sends MOTOR ON before a DRIVE SELECT. **- Most 5 1/4" disk drives do not provide a READY signal but send a DISK CHANGE signal on line 34 of the interface. An 8" drive has provisions for both signals. Likewise, most AT-style controllers expect a DISK CHANGE signal on line 34, so lines 33 and 34 should be connected to lines 11 and 12 of the 8" disk connector. Also, some 8" drives provide a TRUE_READY signal which is more useful than the standard READY. # - Unused on single sided drives (SA-800/801). ##- Used only on hard-sector configured drives (SA-801/851). Some 5 1/4" disk drives have the option of providing _either_ DISK CHANGE _or_ READY on line 34 (in particular, the TEAC FD55R series). Some 8" disk controllers do not care about the DISK CHANGE signal, but must have the READY signal. If you are attaching a high-density 5 1/4" drive to an 8" controller, you may get away with making the drive always ready by shorting lines 21 and 22, but this may cause a few re-tries when switching sides. If your drive offers a READY signal that your controller can deal with, by all means use it. The MOTOR ON/HEADLOAD dilemma may also have an alternate solution if you are connecting 5 1/4" drives to an 8" controller. Some 5 1/4" drives permit motor turn-on by means other than the MOTOR ON signal. For example, the TEAC FD55R series of drives may be configured to turn the motor on based on the state of the IN USE light. The IN USE light can, in turn, be set to turn on only on drive select. Thus selecting the drive automatically turns on the motor and neither a MOTOR ON or IN USE signal need be present. Another way to handle 8 inch drives on a PC is with a Microsolutions Compaticard IV, if you can find one. (MicroSolutions no longer offers this product.) It has the necessary software support to properly handle 8 inch drives, and in both SSSD and DSDD. This controller can be set up as both a primary controller, or as a secondary. It can support 4 drives, of any type, including 2.8 meg. It supports two MSDOS 8 inch formats, SSSD (about 250k) and DSDD (1.2 meg). It works perfectly with 22disk, and can read and write almost any 8 inch CP/M format.