> On Jul 17, 2023, at 12:51 PM, Ethan Dicks via cctalk <[email protected]>
> wrote:
>
> On Mon, Jul 17, 2023 at 12:48 PM Ethan Dicks <[email protected]> wrote:
>> 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
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
