homemade computer for fun and experience... - test-drb@ccmp.vtda.org

4 Apr 1999

While I agree fundamentally in that you really don't have to have graphic
output capabilities, to wit, I did without it for over 30 years of computer
use, I don't believe there's any reason to favor the terimnal over the
direct-mapped monochrome video display.  It's nominally a 2000 character
window that has to be managed, and whether you do it with a terminal or with
a video board is strictly up to you.  I personally believe that exploiting
the approach of the 6545 chip is still a pregnant way to address the problem
of slow video updates due to low (<24.576Mbit/sec) baud rate.

as for what you find difficult to get fixed . . . (a) who cares about fixing
a serial card?  Another costs $3.  (b) pre-vga monochrome cards and monitors
abound at the thrift stores.  Keyboards do as well. (c) so long as hard disk
drives of the ST506 variety still abound in the thrift stores, the
controllers will too.  I passed on an 'AT box a week ago, which had a VGA
card, a 200+ MB eide 3.5" 1/3-height hard disk, and much of the usual stuff
for $10.  Had there been a decent keyboard, I might have gone for it, but
there'll be others next week.

I figure, if I can't replace it with something similar, then I'll replace it
with something more current.

Dick

-----Original Message-----
From: Tony Duell &lt;ard(a)p850ug1.demon.co.uk&gt;
To: Discussion re-collecting of classic computers
&lt;classiccmp(a)u.washington.edu&gt;
Date: Sunday, April 04, 1999 7:26 PM
Subject: Re: homemade computer for fun and experience...

...
 >
> Again, I have to agree about the "waste-of-trees" nature of most
"technical"
...
 > documents these days.  Nevertheless, I find it
easier to understand the
> result of a SPICE simulation when displayed graphically, e.g. with PROBE as
...

There are, agreed, times when a graphical output is essential. I'd hate
it if my logic analyeser could _only_ give a list of the input states for
each sample (although sometimes that's what I want). More often, though,
I want a timing diagram.

My handheld 'scope has an RS232 output that'll send the samples in
memory. Seeing those as a list of values is not often useful. Plotting
them is.

However, the fact remains that often graphical output is _not_ essential.
I can't think why it would be superior to text-only output for
programming, for example. Or text processing - I do all my word processing
using TeX on a text-only machine. WYSIWYG would add absolutely nothing.

> I already stated that the "old" machines did the "old" and in
many instances
...
 > quite persistent tasks well, and still would,
given a chance.  People have
...
 > learned, however, that it's not as beneficial
to have OLD hardware as to
> have new, not because of what it will do, but what it won't.  I don't
mean
...
   that it
won't break.  Any hardware can fail.  It's a statistical reality. 
Although, to be fair, some of the older machines were rather
over-engineered, and less likely to fail than modern PCs...

  However, if you try to repair that old, fine,
terminal you bought in the
 '80's you'll find you can't get it fixed for less than the cost of a PC.

_get_ it fixed? I fix things (anything) myself, and will continue to do so...
...

> If, however, you break your PC, there's really nothing you can't repair
or
...
   replace for
much less than the cost of the original. 
Oh yes? Where do I find an ST506 controller from, new, these days? Or if
I am using a machine that uses such a drive and the controller fails, do
I have to replace the drive _and_ restore from backups as well? That's
hardly a good idea. Ditto for any video card that isn't VGA or higher, etc

Fact is, swapping parts in PCs is easy, provided the PC is absolutely
modern. If it's even one generation behind, you start having problems
finding parts. Maintaining an old machine, where proper docs and spares
are _still_ available is a lot easier.

What if I am depending on some hardware feature of the old card (like the
current loop interface on the IBM Async card. Ever tried getting one of
those, or a clone?

-tony