Re: macADT and .dsk images over 140k

[ferdimh@gmx.de]

On 9 Dez., 22:15, touchstone wrote:

> for example, if i look at $00011b00 to $00011bff, is this the image of
> disk track $11 sector $b?
> and does adt put this on that track $11 sector $b verbatim?
>
> thanks,
>
> matthew
The data is ordered backwards. So the offset $B is logical sector $4
and logical sector $4, is physical sector $7.
The translation is:
logical physical
$0            $0
$1            $D
$2            $B
$3            $9
$4            $7
$5            $5
$6            $3
$7            $1
$8            $E
$9            $C
$A            $A
$B            $8
$C            $6
$D            $4
$E             $2
$F             $F

This skewing increases disk access speed, because the next sector to
be read/written will reach the head just when it's needed.
The "strange" backwards sector scheme simplified DOS somewhat and
since the skewing is optimized for that type of access, ADT uses it
too.