IBM 5100 Restoration in progress

Christian Corti cc at
Wed Mar 18 06:54:53 CDT 2015

On Wed, 18 Mar 2015, Santo Nucifora wrote:
> Where did you find the code for the Bring Up tests?  I would love to have a
> look.  The 5100 Maintenance manual is not very specific and certainly
> doesn't have code in it (unless I missed it).

I disassembled it myself. You can find the disassembly on our FTP server, 
But as mentioned, all information refer to the 5110.

> My registers looks like this:

I don't see anything... was that an attachement or inline picture?

> You'll notice that the first two characters in second line is not right.

They are absulutely right! This means that the processor is running 
(executing a halt instruction that in reality is a jump to itself). What 
you are seeing is the program counter (register R0) changing. I you put 
the machine into single-step mode (there's a switch in the machine under 
the cover) you can step the instructions one-by-one.

> Sadly, it's gotten a little worse after taking this picture so lines 5 and
> 6 have some garbling of the dots. Since I was seeing text, I didn't suspect

If all other characters are ok, what you describe as garbling are just 
changing data bytes.

> the display card right away (again, not knowing the machine) but it may be
> bad RAM on the display card.

I wouldn't suspect the display card, too.

> I'll refer to your  IBMparts.txt file and see what is on that card.  If you
> do see anything else in the registers, I'd be very happy to hear your
> thoughts.

Could you put the picture on your web site or send me an email? And please 
also make the following readable screenshot:
1. Put the machine into single-step mode
2. Press RESTART
4. Make photo

This is the hex dump of the first 512 bytes of the Executable ROS. At 
least that's how it works on the 5110.


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