Yep, I have Sam Revival 21 and have clocked the article on how the
flat 32 bit address space is mapped to a traditional disk-style sector/
track/head layout. I noticed that 2 gb cards aren't officially
supported, but that was the smallest size that I was able to obtain
and seems to work fine, albeit without using all the space. Since
grabbing 800 kb of data from the SD card then rearranging the tracks
such as to interleave them produced a DSK file identical to a
reference copy that I downloaded from the internet (for Fred 34, as it
happens), I am working under the assumption that this isn't a problem
— whether by luck or otherwise.
I have a DSK image of Sam Revival 21's floppy, so will be able to
extract the relevant Trinity B-DOS source and therefore do not imagine
that figuring out how to map to/from B-DOS disk addressing and the
flat address space will be a problem.
However, unless I'm suffering some serious logic flaw, I will then
still need to know the B-DOS disk layout. Sadly SamDisk is closed
source and Sim Coupe doesn't directly deal with the structure as far
as I can tell. Admittedly it had not occurred to me until this second
that it may be hidden in comments in the B-DOS source (sadly one of
the files that Edwin does not offer for download outside of a disk
image). I hope to have access to a Windows PC later in the week (being
currently unaware of any tools for managing disk image contents from
OS X), if not then the SAMDOS format looks quite trivial so I guess I
can just write my own thing. And then post again if the relevant
information is not in there.
On 8 Feb 2009, at 18:55, Colin Piggot wrote:
Thomas Harte wrote:
I'm just trying to put together a quick OS X tool for managing
the 2gb SD card that I'm using with my new and spiffy Trinity
interface - I've been informed by Colin that the cards use the
standard B-DOS layout, identical to the Atom, but I can't
seem to find any documentation on that. Can anyone point
me in the right direction?
The current patched B-DOS for Trinity (1.5t beta 4) only supports up
to 1GB
SD cards at the current time. I've not put in code for switching 2GB
cards
from 1024 byte sectors to 512 byte sectors hence why they are not
supported.
Certainly as far as the SAM is concerned, it is a typical B-DOS
device.
However, if you dump the whole card as a file it's structure and
layout
won't nessesarily be the same as a dumped HD image from the Atom. The
patches I put into B-DOS give the MMC/SD card a fake geometry so B-
DOS can
work as if it's dealing with a HD with head, cylinder and sector
values to
save rewriting massive chunks of Edwin's original B-DOS code, and
then there
are a set of equations that then translate this back to a linear
address
within the SD card for when reading and writing take placed - with a
different equation used depending on the flash card's size and
multiplier
values.
All the changes are documented in SAM Revival 21 and the source code
for the
patched B-DOS is on that cover disk as well as the B-DOS disk with the
Trinity.
Colin
=====
Quazar : Hardware, Software, Spares and Repairs for the SAM Coupe
1995-2009 - Celebrating 15 Years of developing for the SAM Coupe
Website: http://www.samcoupe.com/
