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Welcome, future hacker !
You can use BOTH types of drives. The Amiga chip that handles
disk transfers cannot cope with 1.2Meg format, so it will STILL
send its informations to the drive at the standard speed (880k)
with no care about the REAL drive type.
MAYBE there is a jumper on your drives that lets the embedded drive
controller run ONLY at standard speed rates (that is, NOT 1.2Meg),
but I don't know. Feel free to look around and experiment !
The 1.2Meg 5"1/4 floppies, unlike the 1M44 3"1/2, don't have a second
special hole that tells the drive about the EXACT type of disk.
This second hole also FORCES the drive to write a 1.44Meg.
I remember to have been forced to hide this hole some way
in order to be able to format a bare HD (1.44M) disk to 720k only
(on a Pee-Cee compatible). If I didn't do this, and asked Pctools for
a 720k formatting, the drive refused the procedure.
I know that, during the boot, our Amiga (which is a CLEVER computer,
unlike Pee-Cee) runs a special enquiry to the drives using
/MOTOR, /STEP and /READY signals, in order to sense the kind
of drives attached to the bus. I know that the drives supplied
with our machines can handle this, but I don't know about other
drives intended for Pee-Cees or else.
Note, however, that your drives have 80 tracks, JUST LIKE the
internal drive, so that NO MORE ENTRY should be necessary in the
Mountlist : the drives SHOULD work perfectly with no hack.
Another major difference : most of 5"1/4 drives DON'T HANDLE the
/CHANGEDISK signal, so that the WB will be confused if you
pull the current disk out, insert a new one and try to access it :
a requestor will ask you for the OLD disk again !
In that case, you will have to type from CLI : "DISKCHANGE DFx:"
(x=2 or 3) to tell the WB that you effectively did it.
Then, the hardware side : again, the Amiga drives have a CLEVER
add-on to the basic Shugart specifications concerning the /MOTOR
management. Usually, turning this line ON will run ALL the motors
of ALL the drives. But, maybe for power saving ?, your Amiga will
NOT hold this line ON when accessing a drive : it will STROBE it
with the /SELx line, once to run the motor, once to stop it.
Very clever, but the drives will not work properly without an
"official" hack embedded for DF0: on A500 and DF0:+DF1: on A2000.
This "hack" is regularly embedded into one of the Amiga custom chips
(I forgot the real name) for DF0: management. For DF1: on A2000,
this hack has been added once more onto the main board using
discrete components.
If you want to use your drive properly, you MUST make this hack :
very very easy, it requires a NAND open-collector gate (74LS38)
and a D-LATCH (74LS74). The power supply is taken directly from
external drive connector.
So sorry, I don't have this hack now... I will look for it if you
ABSOLUTELY need it, but it can be found in A2000 schematics at the
disk drive section for DF1: management.
Another solution would be to collect, from died external drives,
the small board that performs this hack for external drives.
You then will only have to make the right cord for your 5"1/4 drives.
Of course, if you want to plug your TWO drives to your Amiga
(named DF2: and DF3:), you should need TWO "hacks". Check carefully
that you use the CORRECT /SELx signal for the DFx: "hack" !!!
One year ago, when I was STILL using my Amiga which now has a looong
rest in France, I used to hook a "brand new but never used for 3 years"
old 360k - 5"1/4 drive to my Amiga as internal DF1:.
As I own an Amiga 2000, the special hack for /MOTOR signal is included
for DF1: so that I only made a "gender changer" to turn the internal
34-pin 3"1/2 style connector supplied for DF1: into the
34-pin encartable 5"1/4 style connector required for my drive,
making a new entry in my mountlist (because of the 40 tracks)...
and let's go !
Though, not very useful to format 440k disks and use them, but
it worked PERFECTLY.
Oh, a last thing : Pee-Cees format their disks with 9 sectors/track
(1 sector = 512 bytes), but Amiga uses 11 sectors/track.
That's why you get 880k/disk instead of 720k/disk for Pee-Cees...
Don't hope for 1.76M with HD disks, because Amiga chips don't handle
the doubled transfer speed (as I said previously).
Amiga
