ajparent1/kb1gmx wrote:
Not a fan of TMS9918, hard to get too.
As I have a large collection of CP/M base systems...
S100 several... (Altair, NorthStar, Compupro)
AmproLB+
Kaypro 2 and also 4/84
DEC VT180 (z80 board + Vt100)
Osborne portable
Epson PS-8...
A good summary, Allison. I too have a pile of vintage systems to look at, plus I've stared at the schematics of lots more. Learn from the experts! :-)
One common thread is that most of the designers were either in tearing hurry, or trying hard to do it on the cheap. When they were in a hurry, we got conservative designs with lots of parts, but poorly optimized (early IBM PC video). When they wanted cheap, we got minimalist hardware that barely worked with serious performance compromises (Sinclair ZX80).
I think there is a third approach in-between these two extremes. You can do more with less, if you have time to be thorough and a high degree of skill. The Apple II and early Macintosh computers were examples of this. Not much hardware; but it did a lot; and without the performance compromises (like the video monopolizing the CPU's time).
NTSC, Try to find a monitor.
I'm aiming for systems that can do NTSC or PAL. If you don't have an old TV or CRT monitor, there are lots of little LCD TVs with NTSC or PAL inputs.
S100 and friends use either 64Char x 16line (processor tech VDM-1) and
similar. Later ones use 80x24/25 (just more parts).
I'm not sure how much resolution is "enough". 32, 40, 64, and 80 chars/line were all common. For a small screen, are the lower resolutions OK? The quality of TVs, monitors, and LCDs can limit the bandwidth as much as the video board.
I happen to like a programmed atmega or two (Grant Searle) as it allows for
VGA, PS2 keyboard.
Lots of people do. It's a common approach, and "fashionable" today, especially if you're using it with a modern micro.
The above also reflects that if you do video you need a keyboard.
Most common keyboards are now USB.
Yes, that is the case. Most people don't want to make a keyboard; they would rather use something they already have. Maybe an old PS2 keyboard, or more likely it's USB.
But the whole point of hacking around old computers is that you should be able to interface whatever you like! Not limit yourself to just what the developer had in mind.
PS2 is hackable; just about any micro can interface it. USB is much harder; you pretty much need a modern micro to talk to it.
Lee Hart
--
A designer knows he has achieved perfection not when there is
nothing left to add, but when there is nothing left to take away.
-- Antoine de Saint Exupery
--
Lee Hart, 814 8th Ave N, Sartell MN 56377, www.sunrise-ev.com
Lee Hart