On yon BIOS settings for my ol Tecra, there's a space for Boot Priority (FDD>CD-ROM>HDD) and a separate space for HD priority (SecondHD > Internal HD).
Does this second HD refer (at least potentially) to a USB hard drive, or some other thing (for instance, I have glimpsed certain references to suggest there's space in there for a second internal hard drive).
Probably to another drive on the same (internal) controller, or maybe to a PCMCIA/Cardbus drive, which "looks" like an IDE drive. Usually if it'll boot from USB or network, it'll say so. Dunno why it says "Second" vs. "Internal", but can't you check Toshiba's website for the specs, or maybe download a PDF of the manual?
Also, what does "IDE" refer to in hard-diskville? In my little (very little) coding world it stands for Interactive Development Environment.
"Integrated Drive Electronics", as opposed to older ESDI, MFM, etc drives where the majority of the "smarts" was on the controller card instead of the drive. By moving the brains onto the drive, it's possible to make various optimizations in drive geometry, track sparing, etc. transparent to the computer. Thus, adding electronics to the drive paradoxically allows the drives to be physically smaller for their capacity and cheaper, and simultaneously makes interfacing them much simpler.
IDE drives are most easily recognized by the number (1) and size/shape of the data connector(s) (consistent within a drive size, such as 3.5").
"IDE" and "ATA" or "ATAPI" are almost the same thing and are sometimes used interchangeably. Wikipedia
has a good explanation. (If it contradicts mine, it's probably right.) Has pictures, tables, the works.
Um, doesn't your "little coding world" include Google, or Wikipedia, or Answers.Com, or ....?
In reference to your implied question about booting from an external drive, if your BIOS doesn't directly support it, you need a "loader" or bootstrap program that knows how to boot from your type of external drive. I've seen them for Linux and I assume they exist for Solaris. Possibly the same program would work for either, if the Solaris disk is formatted appropriately.