Scor­pio News

Re. Drivetec drives

Dear Sir

I found Michael Hendry’s article in the last Scorpio News very interesting and I believe that I may have answers to his two outstanding problems.

1. Slow writing to disk during disk copy

Thad a similar problem to this when fitting 8″ disks with the same track format that he is using. The problem was found to be in the Bios. After a write operation and before doing a step operation, the drive’s electronics require a small delay, so that it can empty its buffers and allow the flux around the head to collapse. In my BIOS this is implemented as a 2 msec delay after EVERY sector write. The fix is to delay 2 msec before each step operation if the last operation was a write. Disk copies will then write at the same rate as the read.

2. Lost sectors if motors have timed out before a write.

If I understand the drive manual correctly, it appears that the sequence the drive goes through is:–

1. motor starts
2. head load
3. 2 index pulses sensed and READY (pin 34) enabled, (But drive may still not be up to speed.)
4. fine stepper centres head on track and READY/​SEEK COMPLETE (pin 4) is enabled

I suspect that Michael Hendry’s Bios is writing to a disk-as soon as READY is active. This means that he may be attempting to write to disk while the heads are still moving or the disk is not yet up to speed.

I think that with these drives the Bios should wait for READY/​SEEK COMPLETE before initiating a read or write command. The motor start may also need up to a 2 sec. delay to allow the motor speed to stabilise.

From the above you may have guessed that I have managed to purchase 2 Drivetec 320 drives (from Matmos).

Yours faithfully, N.C. Back, Burgess Hill, West Sussex.