IBM 5155 analogue display fault

[Tony Duell]

> 
> >From: ard at p850ug1.demon.co.uk
> >
> ---snip---
> >However, I make those modifications as reversable as possible (I would 
> >rather not cut a PCB track, but sometimes there is no other way, for 
> >example). And I don't make them if I don't have to (which is what this 
> >darn thread started off about).
> >
> >-tony
> >
> >
> 
> Hi
>  I guess I'm like you. I have a Olivetti M20 and wanted
> to get the CPM-8000 running on it. The original memory
> cards had 16K DRAMs that gave the system 224K. To run
> CPM-8000 I needed to have 64K DRAMs. It required that I
> unsolder the DRAMs, some capacitors and cut a power line
> to configure for the larger DRAMs.

Sounds like a very reasonable and useful mod to do. This is _certainly_ 
the sort of thing I would do to a classic computer and not worry about 
it. Yes, history is lost, but the benefits (here, being able to run 
CP/M-8000) outwiegh that IMHO. 

Talking of removing decoupling caps when changing from 16K to 64K DRAMs, 
one day I myse repeat the story of how an Epson QX10 graphics board led 
me a merry dance because the previous owner had done the 32K-128K 
upgrade, he'd replaced the chips, moved the links, and then had a machine 
that behaved very oddly...


>  While I would have prefered to get the larger memory
> boards from the manufacture, this was not all that practical.
> I felt that getting working images of the CPM-8000 was
> more important.
>  A computer that doesn't work is an interesting pile of
> hazardous waste. One that works is a window into what was.

No diagreement there!

-tony