Re: external eSata enclosure drive recognition?

Bill Blanton wrote:
"Bill in Co." <not_really_here@xxxxxxxxxxxxx> wrote in message
news:%23Gvwd7T9IHA.1208@xxxxxxxxxxxxxxxxxxxxxxx
Paul wrote:
Bill in Co. wrote:

OK. When the BIOS starts, it enumerates the add-on cards. It visits
them
one at a time, and reads the configuration info from the main chip.

From the "main chip" on the add-on card, I presume that means. (Not
sure
what the "main chip" is, but I guess that depends on the nature of the
card).

The chip connected to the bus present in that expansion slot. The
SIL3132
chip has a PCI Express x1 interface on it, and it connects to the slot.
Probes by the BIOS, to the configuration space of the SIL3132, will
uncover it is a storage controller card. If a BIOS chip is detected,
then the next step would be to load code from the BIOS_chip.

SIL3132 ------ BIOS_chip
|
| (Enumerates via bus)
|
PCI_Express_x1_slot

If the above BIOS chip, has INT 0x13 code present, then that storage
card
could contribute a drive to the boot list.

I wonder if it does (or how many actually do). Interesting.

If the card is designed like this, then a disk drive connected to the
SIL3132 cannot be used to boot the computer.

Cannot? And yet it would appear in the boot list. I don't
understand
why if the system reads the BIOS on the card it's not able to boot the
computer (not that I want that, anyways). It seems you are saying
above
that if the BIOS on the card is read, that it can't be used for booting?
OR
that this is somehow tied into the INT 0 x 13 thing you mentioned, and
THAT
is what creates that limitation?

AIUI, theorectically you could boot the device as long as the BIOS can
load
and jump into the first sector. Practically, "basic disk" Windows MBR boot
code
requires the device to be recognised by the 0x13 interrupts. IOW, Windows
MBR code
uses int 0x13 to load the volume boot sector of the boot device.

So what is the process again? I'm still confused. Let's see what I am
missing:

When you initially boot the computer, the *system* BIOS 1) enumerates
devices, and 2) if it detects BIOS on the added in PCI controller card, the
CPU executes an INT 13H CALL instruction, which then tells it to go out and
read a sector on the MBR of a HD?


.

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