Scor­pio News


July–September 1987 – Volume 1. Issue 3.

Page 62 of 67

There is some talk of Scorpio Systems going into the public domain program supply market, if they do, then perhaps they can have my CAT program, and its companion ADDRESS program to see if anyone wants them. If you don’t fancy sending loot in the direction of Scorpio, then you can pick up those two, and the other public domain programs I’ve mentioned on the CBBSLW bulletin board for the cost of a (long) phone call.

Adding 720K drives to an Amstrad

One last (long) thought, passed on to me by Brian Hayward of Colchester, for those who own Amstrad 1512’s with one drive and haven’t forked out the necessary for the Technical Manual. Statement: If you’ve owned a Gemini or Nascom with 800K disks, bet you’re pretty peeved to discover that the maximum disk capacity of the the Amstrad (most other clones) is only 360K per!! How Brian has both; that is, a one drive Amstrad and the Technical Manual; and he’s found a new command for the CONFIG.SYS file (it actually ends up in the ‘environment string space’) and it goes like this:

DRIVPARMe /D:dd[/F:ff/T:tt/S:ss/N/C/H:hh]

where /D:dd is the drive number (0-255)

and optionally:
/T:tt is the number of tracks/side (1-999)
/S:ss is the number of sectors/track (1-99)
/H:hh is the maximum head number (1-99)
/C indicates changeline (door lock) support required
/N indicates non-removable block device
/F:ff indicates the format factor, where:
0 = 5.25″
1 = 5.25″, 1.2 Mbyte
2 = 720K
3 = 8″ Single density
4 = 8″ Double density
5 = Hard disk
6 = Tape drive
7 = Other

Zap an 80 track drive in the spare hole and, set DRIVPARM correctly, and lo, you have 720K on that drive. Nice, isn’t it.

How do you get 720K per disk on an AT?

Well I run DOS 3.2, so I tried the above on both my AT clone and one of the real genuine IBM AT’s at work with peculiar results! Firstly an AT is fitted with a double sided 80 track dual speed drive, giving 1.2 Mbyte on that drive, made up of 15 sectors of 512 bytes/track. It can also double step the drive and forget about the double speed bit and give the ‘IBM standard’ 360K, double sided 40 tracks, 9 sectors of 512 bytes/track. The snag is that at 1.2 Mbyte, the disks are expensive, whilst 360K per disk is hardly enough to be usable. Wouldn’t be nice to keep drive A as a 1.2 Mbyte drive, whilst at the same time using the drive as 720K logical drive at a different logical address, mainly because I’ve got lots of ordinary disks end very few high density disks. My clone is also fitted with a 40 track Teac as drive B.

So first I set the drive parameters for drive A, 80 track 9 sectors/​track. I used the Amstrad FORMAT.EXE, because a ‘file compare’ showed it was different to my original format program, and as the DRIVPARM ends up in the ‘environment string space’ I figured that the program might actually look there to see what drives it had got. The darned thing paid no notice, it still formatted the drive as 80 track, 15 sectors/track, that is 1.2 Mbyte. So then I set drive parameters to drive B, the Teac 40 track, and lo and behold, the dear old head moved 80 steps (Ok, so as it was a 80 track drive, the last 40 steps were knocking against the end stop), but the disk reported 720K when it had finished. Still it proved that removing the 40 track drive and replacing it with an 80 track would work, but that defeated my aim.

Page 62 of 67