Victor 9000

From: Doug Spence <ds_spenc_at_alcor.concordia.ca>
Date: Fri Jun 20 07:18:31 1997

On Thu, 19 Jun 1997, Roger Merchberger wrote:

> Due to massive amounts of caffeine & sleep deprivation, A.R. Duell said:
> [snip]
>
> >The disk turns at a constant speed. What changes is the speed of the data
> >clock. The bits are sent faster for the outside tracks, so it can fit more
> >sectors on said tracks.
> >
> >I never really saw the point of variable-speed drives. Changing the data
> >clock is a lot easier, and probably faster (getting the spindle
> >up-to-speed and locked at that speed takes considerable time).

<snip>

> >-tony
> >ard12_at_eng.cam.ac.uk
>
> Righto, Tony! There are programs that you can get for IBM PC's that do this
> and you can store 1.8Megs on a 1.44Meg drive!
>
> (Didn't the Apple and Amiga do this with there 800K and 880K drives,
> respectively?)

Not the Amiga, it uses a constant rotation speed and data rate. The Amiga
gets the "extra" space on the disk by simply not using sector headers.
When a sector is needed, the entire track it lives on is read into a
buffer, and when a modification is made the entire track is written back
out.

The lack of sector headers allows the Amiga to write 11 sectors per track,
instead of 9 as with the PC. (In practice, though, I can safely get 12
sectors per track, and I understand it's possible to go higher.)

> See Ya,
> Roger "Merch" Merchberger
> --
> Roger Merchberger | If at first you don't succeed,
> Programmer, NorthernWay | nuclear warhead disarmament should
> zmerch_at_northernway.net | *not* be your first career choice.

Doug Spence
ds_spenc_at_alcor.concordia.ca
Received on Fri Jun 20 1997 - 07:18:31 BST