[rescue] CDROM 512-byte boot questions

[vom513]

Hello all,

I’m questioning my own understanding of this behavior (i.e. boot from a CDROM / 512-byte setting).

I’m using ZuluSCSI SD card emulators on all my machines currently.  ZS has a very nice feature where you can load up multiple .iso images for the virtual CDROM device, and in the config file define the order they will be “inserted” upon an eject.  Using this functionality, I was able to install Solaris 9 without using a real CDROM drive/discs.

Typically on the ZS - I make all my files for the Suns HD3_512.hda, CD6_512.iso etc.  The naming convention assigns the SCSI ID and block size.  However on the multi ISO cycling setup - it seems the ZS doesn’t support setting the block size (yet ?  I have a message on their Github asking about this…)

What threw me for a loop was that the machines still booted just fine and installed with no errors.  The ZS log showed the images were the default 2048 byte block size when first initialized.

According to:

https://www.sun3arc.org/FAQ/cdrom/booting.htm

(very bottom section there…)

A host can tell a drive (assuming the drive supports it ?) to change it’s block size ?

So in that case, that makes my current understanding of what works/doesn't:

- Use a Sun CDROM drive appropriate for the machine/platform in question.  This will guarantee compatibility (i.e. 512)
- Use a non-Sun CDROM drive that supports 512 (ex: Plextor via jumper) will boot.
- A non-Sun drive that can change it’s block size dynamically through a SCSI MODE SELECT command will boot
- A non-Sun drive that doesn’t support 512 in any shape or form will NOT boot.

On my ZS - I enabled debug - and I never saw a MODE SELECT (it supposedly logs all SCSI commands in debug mode).  Nevertheless my SS10 + 20 both boot just fine and installed with no issues.

I understand most of this is are questions for the ZuluSCSI guys.  I will certainly continue to take it up with them.  I just wanted to see if any folks here could correct me or fill in any gaps in my understanding on how this is supposed to work.

Thanks.