From: /G=Owen/S=Smith/O=SJ-Research/ADMD=INTERSPAN/C=GB/@mhs-relay.ac.uk
Subject: Re: Removable mass storage (Syquest,Flopticals...)
Organization: Yale CS Mail/News Gateway
Date: Mon, 23 Nov 1992 17:09:37 GMT

dcw-a@minster.york.ac.uk wrote: 

>Well, according to _Archimedes World_ none of the floptical drives available
>for the arc at this time can cope with normal magnetic media. Bit of a
>bummer really. Although I must admit the source of this information isn't
>exactly famous for accuracy...

I believe that the actual problem is that early flopticals can't handle
disks with sector id's of 0 on them. DOS disks number sectors from 1
upwards, RISC OS disks number from 0 upwards. The firmware in the flopticals
can't handle this. The number of sectors per track and densities is not a
problem I believe (except the flopticals can't handle octuple density ie.
2.88 MB). The firmware should have been fixed by now, but anyone buying a
drive should check carefully before buying as companies may be shifting old
stock. (On the other hand if you don't care and the old ones are cheaper,
fine.) Remember, this is new and not particularly popular technology. Check
out availability of disks (from standard PC suppliers not Acorn scene
advertisers) as a review I read a few months ago in some PC magazine said
that getting hold of disks was harder than they would have hoped.

Syquests are older and more known technology, but their SCSI implementation
has caused problems so make sure that your SCSI card supplier gaurantees
that Syquests work with it. The most important thing is not to try anything
ambitious. Don't spin them down/up in software, and whatever you do don't do
a SCSI disconnect to it. For the Acorn SCSI card I believe you need the
recent upgrade ROM which includes CDFS, or you need to broddle the
disconnects with a SCSI_Op SWI (or use the *disconnect command in Brian
Brunswick's TapeFS).

128MB Magneto Opticals are somewhere inbetween. They're older and more
popular than flopticals, but they're still new enough to be going through
teething problems. The biggest hassle at the moment seems to be
incompatibilities between different manufacturers drives and disks. My
advice at the moment is to only buy disks from the same manufacturer as the
drive, even if the drive manufacturer recommends someone else's disks. Again
check disk availability. Media sellers seem to be pushing Panasonic and
Verbatim, so finding eg. IBM disks could be hard (and cost more). Another
thing to note is there are various different speeds of drives around. Faster
ones cost more.

A problem with all of these types of media is that they are effectively
removable hard discs, which you have to be careful with on RISC OS. You
should always Dismount the disks before taking them out of the drive. Indeed
with the Acorn SCSI/CDFS and motorised eject drives, you can't take the disk
out without dismounting as the drive is locked in software to prevent
FileCore getting upset. RISC OS 3 FileCore can handle the concept of
removable hard disks, but you need a SCSIFS that tells FileCore that it
should expect this and I don't think anyone's SCSIFS has caught up with this
yet.

Personally, I'd put my money in a 128MB MO drive. Syquests are old hat, and
the disk cartridges are physically very big considering the data capacity
(40 or 80MB). Flopticals are too new and too unpopular for my liking - the
PC world seems to be ignoring them. They're also slow compared to Syquest or
MO, plus 20MB capacity doesn't feel like enough to me. The MOs are fast, the
capacity is nicely huge, the disks are physically 3.5 inch, and they're
rapidly gaining in popularity in the PC market. Plus you can put the 3.5
inch CD-ROMs in the 128MB MO drives (the 3.5 inch CD-ROMs are used in
Panasonic and Sony active book type thingies). Whether CDFS can read these
things is a different question, but once the drives and discs become popular
someone will do the software. There's even a standard for a 3.5 inch CD-ROM
with a 5MB(ish) re-writable area on them.

Owen.