Port 0x80

[John Paulsson]

I have this asm program (which prints hardware information) which writes
to port 0x80. Does anyone know what's on that port?

I have a reference that says:

Port 0x80 - Manufacturer systems checkpoint port (used during POST)

Which doesnt tell me much.

Any hardware guru out there with more information about this port?

// jP

[Grzegorz Mazur]

John Paulsson wrote:

During initial tests performed by BIOS POST routines, upon successful
completion of every important testing step, some value is written to this
port. If you put so-called POST card (decoder and two 7-segment displays),
the respective hex number is displayed on it, helping to find the problem in
non-working PC.

The lists of codes are different for different BIOSes, and some
well-known-brand computers used port addresses different from 80h (about 10
addresses total). Today's standard is 80h, but the POST codes still vary
between BIOS manufacturers.

--
G. Mazur
MyWebPage: http://grafi.ii.pw.edu.pl/gbm (x86 and Matrox secrets/tools)
To see my address and employer - read the mail header...

[Ari Lukumies]

John Paulsson wrote:
>
> I have this asm program (which prints hardware information) which writes
> to port 0x80. Does anyone know what's on that port?

It depends on the BIOS of the system. See Ralf Brown's interrupt list,
file PORTS.A. It lists the AMI, AWARD PnP, AWARD non-PnP,
Chips&Technologies and Intel SE440BX variations.

AriL
--
Pain and disappointment are inevitable. Misery is optional.
Homepaged at http://www.angelfire.com/or/lukumies

[Henrik]

John Paulsson skrev i meddelandet ...

|
|I have this asm program (which prints hardware information) which writes
|to port 0x80. Does anyone know what's on that port?
|

|I have a reference that says:
|
|Port 0x80 - Manufacturer systems checkpoint port (used during POST)
|
|Which doesnt tell me much.

Port 80h is one of the DMA page registers; it's unused and BIOSes use
it during POST (Power-On Self Test); if the CPU doesn't boot for some
reason, you now have the last byte written to port 80h that you can use
to look up the reason why it hung/crashed.

[Mike Mccarty Sr]

Actually, you can look up the last part of the POST which passed. That
tells you it died *between* that point and the next checkpoint.

It's an idea, at least, of where it failed.

In article <sdko3ne...@corp.supernews.com>,
Henrik <abcdefghijklm...@alphabet.com> wrote:
)
)John Paulsson skrev i meddelandet ...
)|
)|I have this asm program (which prints hardware information) which writes
)|to port 0x80. Does anyone know what's on that port?
)|
)|I have a reference that says:
)|
)|Port 0x80 - Manufacturer systems checkpoint port (used during POST)
)|
)|Which doesnt tell me much.
)
)Port 80h is one of the DMA page registers; it's unused and BIOSes use
)it during POST (Power-On Self Test); if the CPU doesn't boot for some
)reason, you now have the last byte written to port 80h that you can use
)to look up the reason why it hung/crashed.
)
)
)

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