System and BBC Disk Compatability ?

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ChrisO
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System and BBC Disk Compatability ?

Post by ChrisO »

I'm trying to get my System 3 upgrade working but I'm stuck because I don't have a format disc for it ?

It will read the catalogue off a BBC formated disc but files will not load. I know the underlaying format of the System, Atom and BBC disc is the same but is there some subtlety that stops a BBC disc working in the System (or Atom) ?

Bit of a long shot but does anybody have a copy of the System format disc ? The Atom version might work though I've not been able to find a copy of that either ?

Chris
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danielj
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Re: System and BBC Disk Compatability ?

Post by danielj »

At a guess, the directory needs to be changed to $ (which is root on a beeb) rather than . (which is root on the atom, and also I assume system?)

d.
Last edited by danielj on Fri Mar 15, 2019 7:04 pm, edited 1 time in total.
ChrisO
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Re: System and BBC Disk Compatability ?

Post by ChrisO »

Sadly its not that I knew to change the directory (qualifier in System speak) from $.

I'm getting a Disk error 18 whenever I try to access a file ?
Last edited by ChrisO on Fri Mar 15, 2019 7:29 pm, edited 1 time in total.
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danielj
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Re: System and BBC Disk Compatability ?

Post by danielj »

That's sector not found iirc?
ChrisO
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Re: System and BBC Disk Compatability ?

Post by ChrisO »

A bit more info - looks like the problem is with the BBC using longer addresses ?

If I INFO a file on the System 3 I get: 1900 8023 C1B78 C5B (load address, execution address, length, start sector)
the same thing on the BBC gives: FF1900 FF8023 001B78 05B

My BBC has Watford Electronics DFS 1.42 on it rather than standard BBC DFS maybe thats the problem ?

Would I have this problem with standard Acorn DFS ? Does this problem occur with Atom discs ?
Last edited by ChrisO on Fri Mar 15, 2019 7:52 pm, edited 1 time in total.
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jgharston
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Re: System and BBC Disk Compatability ?

Post by jgharston »

Atom/System DOS *is* DFS, with the exception that:

* DOS defaults to using directory " " (space) and DFS defaults to using directory "$" (dollar). Last time I checked, DFS allows *DIR " ", and DOS allows *SET$ (note: no space), which do the same thing (in opposite directions!).

* DFS uses 18-bit file addresses, DOS uses 16-bit file addresses. The extra 3xtwo bits are stored in the high bits of the sector start, so a DFS file with addresses &FFFFxxxx will be "seen" by DOS as having a sector start way way past the end of the disk and be humungously long. The solution is to ensure DFS files are shorter than 64K and have addresses &0000xxxx.
Last edited by jgharston on Fri Mar 15, 2019 11:08 pm, edited 1 time in total.

Code: Select all

$ bbcbasic
PDP11 BBC BASIC IV Version 0.32
(C) Copyright J.G.Harston 1989,2005-2020
>_
ChrisO
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Re: System and BBC Disk Compatability ?

Post by ChrisO »

Sorted ! The problem was the Watford DFS on the BBC.

This morning I found an old Viglen Utilities disc which has format on it, using this to format a disc it is recognised and works on the System computer so at last I have a working System 3 :D.

I've also managed to get an 80 track PC style floppy (Teac FD55GFR) working just by changing the links to set it to 300rpm.
Kazzie
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Re: System and BBC Disk Compatability ?

Post by Kazzie »

Excellent news. :)
BBC Model B 32K issue 7, Sidewise ROM board with 16K RAM
Archimedes 420/1 upgraded to 4MB RAM, ZIDEFS with 512MB CF card
RiscPC 600 under repair
Acorn System 1 home-made replica
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