On my old PC, I noticed that 0x5 did lots of initializations, but on the actual
one, I couldn't identify what it does. If it does at least chipset-specific
init and 8259s, then this will allow me to reduce the code.
> > One other problem I didn't speak about concerns people using loadlin. Their
> > interrupts might redirect to DOS drivers such as smartdrive, in which case
> > no dump would not work.
>
> There might be a "well-known" BIOS entry point which could help here. I
> don't have the list of BIOS entry points handy but BIOS developers still
> seem to keep compatible with the IBM's original.
There is a well-known bios entry point. The problem is that it depends on
devices and add-on bioses. When you don't have hard disks, you get the
original entry point at 0xf000:0xec59, IIRC. When you have hard disks, this
address becomes int 0x40 and an other pointer replaces int 0x13. This one
should be standard too. But when you have an SCSI card, then you can't know
the pointer. It can be 0xc800:xxxx or 0xd000:xxxx ...
Concerning the possibilities of executing code upon a manual reset, I've
tested it and it doesn't work. The PC simply reboots. I remember that some
chipsets clean all the memory themselves upon reset. But what I can't
understand is why the bios doesn't hang instead of rebooting. Since my
CMOS register contains 0xA or 0x9 or anything else, the bios should notice it.
I can't imagine that the reset also clears this flags !
Perhaps we should try an NMI. Anyone has a "red button" connected to NMI input ?
(a hardware debugger did that at the time of my old 8088).
Willy
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