[rescue] CDROM 512-byte boot questions

[John Hudak]

Interesting information. TY. I am considering getting a ZuluSCSI board
since the SCSI2SD v5 is NLA.  Do you endorse it?
Thanks
J


On Thu, Jul 27, 2023 at 4:01 PM vom513 via rescue <rescue at sunhelp.org>
wrote:

>
> > On Jul 27, 2023, at 12:54 PM, Jonathan Sturges via rescue <
> rescue at sunhelp.org> wrote:
> >
> > Hi,
> > Nice summary, your understanding is correct.  Some small additions:
> >
> > *  Some OSes -- Solaris2, I'm fairly sure, maybe later SunOS? -- the
> SCSI drivers can issue the block size change command when the OS is running
> (or are able to handle the 2k block size).
> > *  OBP 3.x can issue the block change command too, IIRC; it's really OPB
> 2.x and prior that have the hard requirement of a 512-byte block
> requirement for booting.
> > *  Besides Plextor, most Panasonic, Toshiba and Pioneer drives have
> jumperable block sizes.
>
> Thanks for the reply/confirmation.
>
> I did a bit more experimentation with the ZuluSCI and figured I’d post my
> results to the list to benefit any future folks who might be looking for
> this type of info.
>
> - CD6.iso : Zulu log shows it coming up in 2048-byte mode, but my sun4c/m
> machines boot fine from it.  I don’t see a MODE SELECT in the log - I guess
> the ZS is just operating in “soft” block mode and honoring whatever request
> comes in ? (This is great by the way - not looking a gift horse in the
> mouth)
>
> - CD6_512.iso : Block size specified as 512.  Works as expected.
>
> - CD6_2048.iso : Block size specified as 2048.  Machines will NOT boot.
>
> So it seems like _<BLOCKSIZE> is a “hard” setting.  Omitting this seems to
> run the device in “soft” mode (hard/soft just my personal terminology for
> this behavior).
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>
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