> On Feb 1, 2022, at 5:02 AM, Liam Proven via cctalk <cctalk@classiccmp.org>
> wrote:
>
> ...
> I suggested making a D: drive and putting the swap file on it -- you
> saved space and reduced fragmentation.
>
> One of our favourite small PC builders, Panrix, questioned this. They
> reckoned that having the swap file on the outer, longer tracks of the
> drive made it slower, due to slower access times and slower transfer
> speeds. They were adamant.
And very obviously wrong -- elementary geometry.
It is true that the outer tracks are physically longer. But that doesn't mean
transfer rates are slower. Given the older formatting where the count of
sectors per track is constant, so is the transfer rate -- the same number of
sectors pass the head per revolution, i.e., in constant time, no matter what
track you're on.
The bits are physically longer, of course. That's why later drives put more
sectors per track as you move outward, and that means that the transfer rate on
outer tracks is *higher* than for inner tracks. And some storage systems
indeed use that knowledge.
Incidentally, while constant sector count was the norm for a long time, it
wasn't universal; the CDC 6603, in 1964, had "zones" with the sector count
changing between zones. Outer zones had more sectors per track. Unlike modern
drives, the OS driver had to handle that.
paul
