IBM ROM BASIC or lack thereof

From: Hans B Pufal <hansp_at_aconit.org>
Date: Sun Sep 30 00:36:32 2001

Glen Goodwin wrote:

> Tony, I think you are correct as I've never seen a clone mb with BASIC in
> ROM, but I *have* seen clone boards -- including early Pentium boards --
> which would cough up "no rom basic" if they didn't find a bootable device.
> Oddly enough the text of this message is always displayed in 40-column
> low-res mode. Doesn't this suggest that part of the ROM BIOS code was
> "borrowed" from early IBM code?


On early IBM machines, ROM Basic was entered by performing an INT 18h
instruction. On machines not implementeing ROM Basic, calling int 18
would simply display the "no rom basic" message, often in 40 col mode
since that was the lowest resolution suupported.

Many bootstraps terminate with a call on Int 18 to indicate the absence
of bootable code on the media hence the message would appear.

[OT] On modern PCs, Int 18 is still used to signal that a bootsrap has
not found an operating system but now the BIOS retains control and tries
the next boot device in the list defined by the user. If no OS is found
a message to that effect is displayed.

  -- HBP
Received on Sun Sep 30 2001 - 00:36:32 BST