DVD-RAM on FC3
amilivojevic at pbl.ca
Tue Mar 8 16:27:46 UTC 2005
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
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
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