IBM PCJr port 10h and 11h

[vladstamate]

I am looking at some disassembly for the IBM PCJr BIOS and I see it outputing to ports 10h and 11h. What is at that address in a PCJr? I do not see the IBM PC BIOS doing that. The BOCHS port list (http://bochs.sourceforge.net/techspec/PORTS.LST) does not have it, it only mentions the DMA controller on a PS/2 model 60 and 80 (which are AT class machines).

Anyone know?

Regards,
Vlad.

 

[eeguru]

10h is POST. Not sure about 11h.

 

[vladstamate]

Thank you. POST as in POST code, like error code?

Vlad.

 

[eeguru]

Thank you. POST as in POST code, like error code?

Same as port 80h on a PC. BIOS write progressively decrementing numbers to port 10h as it is going through it's basic hardware test. If you have a something that latches and displays the last value written to port 10h, you can determine at which point in the BIOS code the computer locked up.

 

[vladstamate]

Thank you. I understand now, that is what I was looking for.

 

[Trixter]

Are you looking at a disassembly, or the source code? The source is available: ftp://ftp.oldskool.org/pub/misc/Hardware/IBM/IBM PCjr Technical Reference.pdf

There are definite status outputs to 10h, but I didn't see anything outputting to 11h...

 

[vladstamate]

Ohh, that is a nice PDF file, thank you Trixter!

Are you looking at a disassembly, or the source code?

Neither actually, I've noticed this while running the PCJr BIOS in my emulator.

Vlad.

 

[Trixter]

Neither actually, I've noticed this while running the PCJr BIOS in my emulator.

A new emulator! Well, you know what my first question is: Does it run 8088 MPH?

 

[eeguru]

As I heckled you about before your talk, you must finish the Jr port first! Non-negotiable!

 

[Scali]

As I heckled you about before your talk, you must finish the Jr port first! Non-negotiable!

Nah, the PCjr has other capabilities, better to make something new

 

[vladstamate]

Haha, no Trixter, it does not

 

[Trixter]

As I heckled you about before your talk, you must finish the Jr port first! Non-negotiable!

Drat!!