DVD-RAM on FC3

[Aleksandar Milivojevic]

Rick Stevens wrote:

> Well, way back when, Sun used a 512-byte
> sector size on CDs, too (Sun SPARC SLC, etc.).  I never did figure out
> why.

It was a hack to be able to boot from CD-ROM.

Old SPARC boot code can boot only from disks that have 512-byte sector 
size.  When CD-ROMs become popular, the only way to boot SPARC machine 
off CD-ROM was to use 512-byte sector size.  Since back than you 
couldn't simply flash new version as you would do on newer machines, you 
were stuck with version you got on the motherboard.  I don't know if 
SPARC machines were the only ones with that problem, but almost all SCSI 
CD-ROM drives from that era have jumper that controls the sector size 
upon power-on (name for the jumper is not standardized, and sometimes is 
confusing, "block" is often used, and I saw some drives that had it, but 
it was not mentioned anywhere in documentation).

Once the OS is up and running, it can use either 512 or 2048-bytes 
sectors.  So you need that "special" CD-ROM drive only if you want to 
boot from CD-ROM media on an very old SPARC machine.

Basically all Ultra machines, and probably SS5/10/20 (not sure for all 
of them) can boot from any CD-ROM drive.  Anything older, and you 
probably need 512-bytes per sector capable drive.

Also, on most CD-ROM drives from that time you can swtich from 512 to 
2048 and back using more or less standard SCSI commands.  Later versions 
of boot PROM can also boot from both 512 and 2048 bytes per sector media.


-- 
Aleksandar Milivojevic <amilivojevic at pbl.ca>    Pollard Banknote Limited
Systems Administrator                           1499 Buffalo Place
Tel: (204) 474-2323 ext 276                     Winnipeg, MB  R3T 1L7