1 Feb
2022
1 Feb
'22
9:20 a.m.
On Feb 1, 2022, at 5:02 AM, Liam Proven via cctalk
<cctalk at 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