8" description pc floppy 2 side select 32 10 seek complete n/c 12 restore " 14 eject " 20 index 8 22 ready 34 24 motor on 16 26 ds1(drv select) 10 28 ds2 12 30 ds3 14 32 ds4 6 34 step dir 18 36 step pulse 20 38 write data 22 40 write gate 24 42 track 0 26 44 write protect 28 46 read data 30 all other even pins are not connected all odd pins are earth/ground
With some 'wire weaving' in the ribbon cable - going from 50 to 34 - it is quite possible to substitute a 5.25" high density drive for an 8". That is what they were originally designed for, to be a functional replacement for the 8" DSDD.
********************************************************************
The following table is extracted from the CompatiCard manual:
Card 34 37 50 8 Inch Drive
Signal Name Pin Pin Direction Pin Signal Name
========================================================================
Programmable 2 3 ---> 2 Low Current
Index 8 6 <--- 20 Index
Drive Select 1/3 12 8 ---> 28 Drive Select 2
Motor Enable 1/3 16 10 ---> 18 Head Load
Step Direction 18 11 ---> 34 Direction Select
Step Pulse 20 12 ---> 36 Step
Write Data 22 13 ---> 38 Write Data
Write Enable 24 14 ---> 40 Write Gate
Track 0 26 15 <--- 42 Track 0
Write Protect 28 16 <--- 44 Write Protect
Read Data 30 17 <--- 46 Read Data
Select Head 1 32 18 ---> 14 Side Select
Connect odd number pins of 34 pin connector to odds of 50 pin connector
Connect pins 21/37 of the DB-37 to all the odd pins on 50 pin connector
************************************************************************
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, then, is a diagram for a basic conversion cable to allow con-
nection of an 8" drive to an IBM-compatible, AT-style (high density)
controller.
This diagram also works in the other direction--that is, to attach
high-density 5 1/4" drives to an 8" 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
Notes:
* - This has not been tested by me. 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, I assume that a controller sends MOTOR ON before a DRIVE
SELECT (my 8" controller will send HEAD LOAD before 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. I have heard that
this may cause a few re-tries when switching sides, but it works fine
for me. 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.
John D. Baker ->An Apple ZCPR3 nut //
8 January 1991
Revised 12 March 1992
Annotated (#,##) by Don Maslin
17 Oct 1995
Limited HTML formatting by:
F.T. Gowen
Last modified: 26th. August, 2001