> It's pretty silly when folks write articles like this and don't bother to
> do even the minimum of research, which would have revealed that there are
> plenty of BBC Micros still in existence. If the writer is referring to
> the video disc player (which would make more sense) then I can believe
> that there may only be a "handful" of complete systems left in existence,
> but this begs the question of why, inspite of them, this makes the
> videodiscs "unreadable".
There's more technical info at
http://www.atsf.co.uk/dottext/domesday.html
The videodisk players were specially modified for this purpose.
"The data channel appears on a SCSI bus ... and SCSI had only just been
standardised at this time. This means that the player looked to the host
computer like a very large, somewhat slow, read-only hard disc. We had
never used a CD-ROM at that point. A read-only version of the BBC Micro
hierarchical disc filing system, now called VFS (for Videodisc Filing
System), is used to access the data in a way that adhered to the filing
system standards. In this way any code written for one filing system
could be used with another, providing both use the same subset of the
whole standard. Write-only systems obviously do not have sector write
primitives or means of modifying file attributes for example."
It sounds like images were stored as PAL frames and were converted to RGB
for mixing with the BBC RGB output.
Eric
Received on Thu Mar 07 2002 - 17:10:27 GMT