Steve McCrystal wrote:

>** Reply to note from Mike O'Connor  Sun, 21
Mar 2004 08:56:12 +1000
> 
>Mike,
>  
>
>>RTC values are stored in the CMOS-RAM, along  with all the variables 
>>selected from the [firmware{EEPROM or Flash  based}] BIOS menus 
>>
>One of the changes I mentioned.  I'm sure you're old enough (like me
:^)) to remember when it was the other way around... CMOS was in the RTC
chip, a;; 64 bytes as I recall.  Damned if I can remember the most common
maker, tho.  It was a REAL common term years ago. 
> 
>
DALLAS RTC!

>>the shutdown status byte  
>>    
>>
>What the heck is this?
>

Hi Steve,
The *shutdown* byte holds the *hardware* status of the machine - 
interpreting these byte values varies from one BIOS manufacturer to 
another except for certain values which are consistently used ;

0 = Proceed with normal POST (soft reset)
1 = Initialize chipset for real-mode operation
2 = Shutdown after memory test
3 = Shutdown with memory error
4 = jump to disk bootstrap routine
5 = Jump to DWORD pointer at 40:67h (EOI** was issued and keyboard has 
been flushed)
6 = Jump to DWORD pointer at 40:67h (no EOI** issued)

 etc.

8 = Return to POST memory test
9 = Return to BIOS extended memory block move (Interrupt 15h, function 
87h was in progress)

** EOI = End Of Interrupt - issued to the Interrupt Controller.

Basically tells the computer where the system should return after a 
system shutdown occurred.
It's used by the BIOS to go through a reset and possibly take alternate 
action other than a normal reset.
Also useful for returning to real-mode from protected mode by issuing a 
reset.
For code 5, the user must also restore the interrupt mask registers.

That gives you maybe a bit of an idea how important the CMOS register 
contents are.

-- 
Regards,
Mike

Failed the exam for
--------------------
MCSE - Minesweeper Consultant and Solitaire Expert
--------------------
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[Please use zipped versions of above]




 
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