SAC.DYESGPF@E.ISI.EDU (11/08/88)
Concerning the questions on hooking a 3.5 inch 1.44 meg drive to the Z100
8 inch controller, I can provide some of the information you are looking for.
I am currently waiting for such a drive to arrive [ a Mitsubishi 8-) ].
Until the drive arrives and is installed I will not be able to check on the
number of bytes per format track (gaps, indexs, markers and data). While it
is possible to squeeze 18 sectors of 512 bytes and the required indexs, etc
within the 292E hex byte of the 1.2 meg (AT and Z100 8") it would be a bit
cramped, will know more about this soon (IBM bios does not seem to have a
Read-track function like the Z-100 function 7 for bios call 40:48).
Now for what the information I have collected so far:
1. Pin #2 must *NOT* be connected to the controller, leaving it discon-
nected provides the proper head current for the 1.44 meg format. This is
also true for the 1.2 meg AT drives. If you want to use this drive for 3.5
inch 720k you will need to add a switch to connect pin 2 to any of the odd
number pins on the drive. Head current must be low for 720k and high for
1.44 meg.
2. Pin out is the same as for the standard 360k 5.25 inch drive with the
exception of pin 2 as noted above {odd number pins are all ground and all
even number pins which are not shown are not connected (NC)}:
8 " 3.5 "
Description Cntlr Drive
Track > 43 . . . 2 . . NC
Two-sided. . . .10 . . NC *
Side 1 select. .14 . . 32
Head load. . . .18 . . 16 (Motor on)
Index. . . . . .20 . . 8
Drive ready. . .22 . . NC
DS0. . . . . . .26 . . 10
DS1. . . . . . .28 . . 12
DS2. . . . . . .30 . . 14 +
DS3. . . . . . .32 . . 6 +
Direction. . . .34 . . 18
Step . . . . . .36 . . 20
Composite write 38 . . 22
Write gate . . .40 . . 24
Track 0. . . . .42 . . 26
Write protected 44 . . 28
Composite read 46 . . 30
* Connect pin 10 to any odd numbered pin
at the controller end of the cable.
+ On drives intended for ATs these pins
will probably not be connected.
3. Bios Paramater Block (obtained from a 1.44 3.5" formated on a Z-248
using a PROCOM(r) drive kit, device driver and format program):
Bytes/sector . . . . 512 . WORD
Sectors/cluster. . . . 1 . BYTE
Reserved sectors . . . 1 . WORD
Number of FATs . . . . 2 . BYTE
Directory entries. . 224 . WORD
Total sectors. . . .2880 . WORD
Media descriptor . . 0F0h. BYTE
Sectors/FAT. . . . . . 9 . WORD
Sectors/track. . . . .18 . WORD
Number of sides. . . . 2 . WORD
# of hidden sectors. . 0 . WORD
4. Software concerns:
a. Format version 3.01 for the Z100 (supplied with MS-DOS 3.10) will
not format anything other than the normal Z100 formats.
b. Chkdsk appears to accept the BPB as modified by RD200 when used on
an AT formated 1.2 meg 5.25 floppy. Will test on the 1.44 meg later.
c. Diskcopy - unable to test at this time but will probably have the
same limitations as Format. Possibly something like Xcopy might be better
anyway.
5. Patches:
a. A few changes to RD200.ASM may be all that is need to read and write
the 1.44 meg format.
b. Running RD200.COM with DEBUG provides enough information to make
permanent changes to bios if desired. The key section of code in IO.SYS
3.00 begins at offset 719h (offset from start of file). Looking at the code
from 719h to 77Fh there appears to be a possiblity of patching bios in a way
which would allow using both the AT and the Z100 1.2 meg formats at the same
time. This should also allow having one 1.2 meg and a 1.44 meg drive each
using the appropriate formats. A viable option would also be a device
driver a-la DRIVER.SYS supplied with MS/PC-DOS 3.21 (BTW - does anyone know
if 3.21 is/will be available for the Z100).
I have started work (in my spare time) on a formatting program for AT style
1.2 meg and 3.5" 1.44 meg formats. Probably wouldn't be too hard to include
a 720k format but there is probably a program already available which does
this. If anyone has already written a program to do all or part of this, I
would appreciate hearing from you. No sense in re-inventing the wheel. My
approach has been "bottom up" using assembly for the disk i/o routines
(Format track, Write sectors, Verify sectors, etc.) and MicroSoft Pascal for
things like building the track data and manipulating the CHRN values.
I hope this has provided a few answers for the original poster and some of
the information Gern wanted. After my 3.5" drive arrives I will post any
additional information, including the success of RD144 (modified RD200).
Al Holecek
<SAC.DYESGPF@E.ISI.EDU>GUBBINS@RADC-TOPS20.ARPA (Gern) (11/09/88)
Thanx for the great 1.44M 3.5 drive info! Are you planning to put the 3.5" on the 8" or 5.25" connector? Any ideas as to the RPM or how many tracks/side the 3.5 1.44M uses? Gern -------