17 Jul
2023
17 Jul
'23
10:05 a.m.
On Jul 17, 2023, at 12:51 PM, Ethan Dicks via cctalk
<cctalk(a)classiccmp.org> wrote:
On Mon, Jul 17, 2023 at 12:48 PM Ethan Dicks <ethan.dicks(a)gmail.com> wrote:
I don't know what to make of that web page's description, it certainly doesn't
have much connection to reality. Are those numbers supposed to represent the placement of
logical sector numbers onto the physical track? If so, they show 5:1 interleave rather
than 2:1 interleave. Or do they represent the physical sector numbers for consecutive
logical sectors? If so, it seems to be backwards.
The actual algorithm is what I wrote in my previous email, which you can also find in my
RSTSFLX tools. That has been tested against real world RX50 floppies, and against the
source code of the RT11 RX50 driver.
paul
From: http://www.chdickman.com/pdp11/pro380.txt
"The RX50 floppy starts at track 1. Track 0 is logically placed after
track 79. The sectors are interleaved 1, 3, 5, 7, 9, 0, 2, 4, 6, 8,
10. The track shift and interleave must be taken into account when
moving disks between real PDP-11 and emulators."
Let me point out that this webpage quote accidentally lists too many
sectors for an RX50.
It should be "... interleaved 1, 3, 5, 7, 9, 0, 2, 4, 6, 8..." There
is no "sector 10" when counting from 0.
-ethan