XT only seeing half the disk

[silcreval]

Hi

I'm trying to setup a hard-drive in a IBM XT. Its a type 13 'WD25' drive
which I believe is around 20M formatted.

I've replaced the original non working controller which was a 62X0786
with one which looks identical but has the number 6135984 instead.

I've noticed that the new board doesn't have the DIP switch, although there
is a place for it.

Now the new board does work, and the drive can be setup with fdisk
and format. However, it only formats to 10M. Looking at the format it
only appears to be seeing heads 1-4 (the WD25 has 8 heads).

Apart from getting a different controller - is there anything else I can do

I could remove the DIP switch and ROM from the old board and transfer
to the new (working) board, but suspect that might not work?

Thanks.

 

[frozenfire75i]

Hello no there is northing you can do but get a new card if you want to use the full size of the disk, you have the stock IBM MFM HDD con. card, and it's designed for one hard drive only the 10MB ST-412. So to fix your problem you need go and find a diff. MFM Card, such as the WD XT GEN!

 

[MikeS]

If you're reasonably confident that you can move the ROM and switch without damaging the working one, why not try it? If the boards are really otherwise identical it oughta work; as a matter of fact, you could just bridge the appropriate pads with jumpers (and cut any unneeded ones) and forget about the switch.

 

[modem7]

The early cards support the following four drive geometries, but because the controller lacks the switch block to select the drive, the final drive type is the one used.

 Cyl Hds WPC  Ctrl
 ----------------------
 306  2    0   00
 375  8    0   05
 306  6  256   05
 306  4    0   05  (e.g. ST-412 [10MB])

The WD25 is a type 13 drive, which means: 306 cyl, 8 heads, WPC of 128
There is no match, and so the possibility of keeping the original ROM in the 6135984 card, and only soldering switches/jumpers to select one of the other supported drives is not valid.

Therefore, like MikeS, I think your idea (move both ROM and switch, or move ROM and solder on jumpers) is worth a try.