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Using An 8BS CD on an Archimedes

By Martin Hodgson


The 8BS CD-ROM collections of BBC disc images are produced on a Wintel (Windows / Intel / AMD / etc) computer. Since DOS does not have a proper filetyping system (but does have the three digit file extensions) none of the disc images on the 8BS CD-ROMs, and other Wintel originated resources, can be recognised automatically by ImageDFS or any other utility on an Acorn RISC-OS computer. It is necessary to copy the image files to your hard disc and filetype them (as BBCSnap, i.e. &B22). ImageDFS will then open the image files and allow you to use them.
However, Paul Gardiner of Warm Silence Software has written to me, following my query as to possible modification to ImageDFS to enable use of the disc images straight from the CD, as one can do on a DOS / Windows machine running pcBBC, for example. His letter gives the solution to the problem, as follows :
        "The problem with accessing images from CD-ROMs is solvable by methods other than altering ImageDFS. We now sell a replacement for CDFS called CDROMFS. Its main purpose is to allow access to the latest Windows95 CDROMS, but it also solves the filetype problem (allowing the user to set up a file extension to filetype mapping). There is also a freeware patch for CDFS, called CDFix, which just solves the problem by patching CDFS."
Following this advice, I found a copy of CDFix. It has been around for years and is on many Acorn discs from various sources, including magazine discs and the PD libraries, and on several Acorn related Internet sites.
I opened the CDFix directory (hold SHIFT and double click on the name), then loaded Edit, and dragged the text file
"Mappings" into it.  At the end of the Mappings file I added "SSD &B22". On the next line I added "DSD &B22", and saved the file  back into CDFix. This maps the image file extensions used by Chris, to the filetype recognised by ImageDFS.
Double clicking on CDFix loads the filetype mappings (nothing visible happens). After ImageDFS is loaded, opening a directory on a CD which contains files with the file extension .SSD or DSD now shows the files with an icon of a black 5.25" floppy disc. Double clicking one of these image files opens it up like any. other directory, giving you access to the original files contained therein.
If you load the BBC emulator, 6502Em, you can change the currently selected directory in 6502Em to the CD by typing "*DIR CDFS::0", followed by *DIR <image filename>" . You can then *CAT the contents and LOAD or RUN any file. If the image is of an autobooting disc, the just use SHIFT + BREAK to run it in the usual way.
So now I can use the 8BS disc images in a completely transparent way, as if they were real DFS discs on the CD-ROM.
ImageDFS will read single-sided disc images, and those where side 2 is joined on after side 0. It will not handle interleaved double-sided images yet. WSS might rectify this if a few people contact them ...
Incidentally, apropos of BBC emulators on RISC-OS machines, the emulator, 65Host, supplied by Acorn years ago will not run on the RISC PC range. There is a patch for this available from various Internet sites which solves that problem. However, if you have a StrongArm processor the patched 65Host still does not run. I have managed to do a further patch, using pcr13 and/or NoDisc ( I forget which one or both). My copy of 65Host now seems to run OK on my StrongArm'ed RISC PC. It is worth a try. Contact me if you have problems ( at meh@publiconline.co.uk ).
Regards,  Martin Hodgson   D7X

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