Archiving Software

[Christian Corti]

On Sat, 17 Dec 2005, Dave Dunfield wrote:
> Or is there a reason why your 8" and 5.25" 48TPI disks can't be run at the
> standard PC drive A: and B: positions?

Because some on-board FDCs don't support FM. Honestly it's very nasty to 
open the PC and jumper the secondary FDC to the primary address and 
disable the on-board FDC and change the BIOS setup...
BTW it's not complicated at all to support a secondary FDC (shut down the 
primary if it's on the same DMA), the programming is the same.

> Because 4 FDDs on one controller is not a standard PC configuration. 
> Does your controller use the internal drive select register of the 765? 
> Does it have an external hardware register like the 2-drive select 
> register of the PC, and if so what is the layout and will it be the same 
> on different 4-drive controllers. Why does your controller have two 
> connectors (there are four drive selects already on the cable).

It must be some kind of standard, otherwise it wouldn't be supported by 
the stock DRIVER.SYS with MS-DOS. I've just checked my card: it's a 
multi-I/O 16-bit ISA card with IDE, two serial, one parallel and one FDC 
(it's a Motorola MCCS3201FN), the serial/parallel stuff if handled by a 
SiS 82C452A. There's a jumper for the FDC to be at 3Fx or at 37x, and so 
on. The only label on the card says "IFSP-2.10". It has two connectors 
because it also has four motor-on signals. You know that the four drive 
selects on the connector are divided into to two select and two motor-on 
signal. So you need two connectors for four drives.
Just have a look at the data sheets for e.g. the DP8473 and the i82077: 
they all support four(!) drives, and it's documented, and it is realized
the same way. The PLCC version of the DP8473 (the common version) has DR0 
and DR1 on pins 6 and 5 (drive select 0 and 1), *and* DR2 plus DR3 on pins 
45 and 43 respectively. And for the motor-on signal, MTR0 (8), MTR1 (7), 
MTR2 (1) and MTR3 (52). So connecting the unused pins on a card to a 
second 34 pin header gives you two more drives! The drive select and motor 
on signals are available in the digital output register (DOR), bits 0 and 
1 contain the binary encoded drive number (0-3), bits 4 to 7 the 1 out of 4 
motor-on lines.
Now for the i82077: drive selects are on pins 58,62,64 and 67, motor-on 
signals on pins 57,61,63 and 66, same register (DOR), same use.
Now for the uPD765: No good design for the PC uses the on-chip drive 
selects, and there are no on-chip motor-on signals, that's why there is an 
additional register (e.g. SN74174) on board that holds these signals, 
therefore called the "digital output register" (see e.g. the "HP Vectra 
Technical Reference Manual Vol.1" from 8/1985)

> I don't think this is all that common a setup, and most people will find 
> it easier to just hook up the required drive long enough to make the 
> images that you need. (I provide details on my site on how to set up a 
> nice external drive cable).

I've setup my PC to be a multi-media machine, i.e. it can handle 
multiple medias from 8" down to 3.5", it has a paper tape reader, a Facit 
4070 paper tape punch, QIC tape drives, SCSI, and even an external dual 
5.25" floppy drive that runs CP/M internally (yes, that's right, it's the 
floppy drive for the Mupid with Z80, 64kB of RAM, and a serial port to 
hook it up to the PC, BTW. the format is 96tpi single-sided FM).

> I do apologize for burdening you with this.  However the image file format

I'm sorry if it sounded like a complaint, it wasn't meant to be one.


Christian