Track Formats

General discussion forum - for all that doesn't fit in any other category.
Post Reply
Beery
Posts: 2
Joined: Thu Aug 24, 2017 8:11 pm

Track Formats

Post by Beery » Thu Aug 24, 2017 8:27 pm

I recently got the HxC Rev. F drive for use with a TI-99/4A. The Geneve 9640 uses the same disk format as they were compatible units with the Geneve 9640 being an upgraded and faster version of the TI-99/4A.

Back quite a few years ago, someone developed a program for formatting diskettes that besides setting up "interlace", also added "skew".

I do not recall what the specific interlace was the default for the TI-99/4A, however let's pretend it was 9. Thus, to read 9 sectors x 256 bytes of a single density track, the disk media had to rotate 9 times. At 300 rpm, This required 1.8 seconds to read a track.

A software developer with a lot of knowledge of drive control behavior, wrote a program that did two things. One could optionally change the interlace. With the Geneve 9640 computer being faster, it was able to read in the disk contents as fast as the disk drive could turn. Thus, to read in 9 sectors on a 1 interlace track, it would take only 0.2 seconds. In addition, with the proper skew timing which created a slight delay for the head step to the next track, the first sector of the next track would be ready for reading without the drive having to turn a full revolution to get back to the first sector of the next track.

As the Geneve 9640 used a bootable operating system similar to MS-DOS, this changed the required boot time because of the special layout from something close to 45 seconds to less than 5 seconds.

Is there someway to implement this capability into the HFE format or to "boost" the read speed when the device it is plugged into can handle a faster data stream?

Thanks for the feedback.

Beery Miller

Jeff
Site Admin
Posts: 5683
Joined: Fri Oct 20, 2006 12:12 am
Location: Paris
Contact:

Re: Track Formats

Post by Jeff » Fri Aug 25, 2017 9:14 pm

If you format the HFE file with the machine you should theoretically have the exact same disk geometry and then the expected read speed.

Beery
Posts: 2
Joined: Thu Aug 24, 2017 8:11 pm

Re: Track Formats

Post by Beery » Thu Dec 14, 2017 11:46 pm

FYI,

I finally got a suitable controller that worked with my software. The HxC did accomodate the new interlace/skew properly. I was able to format the HFE image to a new interlace and skew without issue.

Great product!

Beery

Post Reply