Chuck writes:
> Ok, so a couple of people have pointed out that the Plextor's support 512
> byte sectors. Further the Plextor CD writer also supports 512 byte sectors.
> So my question is can I use it to write a bootable disk image? Has anyone
> tried this? Tim?
The actual sectors on the CD-ROM are *always* really 2048-byte sectors.
Setting a CD-ROM reader to 512 bytes/sector just splits each real sector
into four. And many SCSI CD-ROM drives will gladly do this via a SCSI
mode select command (though not all VAXen issue the command, nor do all
drives pay attention to it!) and with some you can do it with physica
jumpers instead (or also.)
(Actually, I'm reluctant to call the information on the CD as "physical
sectors" since really the data and error correction information are interleaved
and spread out over the spiral, so that a scratch in one place won't
ruin all chances of recovering the data via ECC. The point is, a CD-ROM
is a bunch of blocks, just as a hard drive is.)
At write-time, all CD-writing software that I know of does things in terms
of 2048-byte sectors. Even the CD-writing software that runs under VMS
(for example, "cdwrite" and "cdrecord".)
If you're really bored you can learn how to do mode page editing on SCSI
drives yourself. I learned it a couple of years back when I got a boatload
of Micropolis 1.6Gig drives that had been set for 520-byte sectors and
wanted to use them in a more "normal" 512-byte mode. Since then the
skill has come in handy to connect modern, fast, and "large" (i.e. 9
Gbytes or larger) SCSI drives onto systems that don't deal with drives
that large. Just go in, edit the disk capacity mode page, and you've
got a smaller than 1 Gig drive that never has to seek very far :-).
--
Tim Shoppa Email: shoppa_at_trailing-edge.com
Trailing Edge Technology WWW: http://www.trailing-edge.com/
7328 Bradley Blvd Voice: 301-767-5917
Bethesda, MD, USA 20817 Fax: 301-767-5927
Received on Thu May 04 2000 - 14:11:54 BST