24 Apr
2007
24 Apr
'07
8:36 p.m.
On Tue, 2007-04-24 at 12:01 -0400, Ethan Dicks wrote:
Video card manufacturers often produced games. Probably the most
common target video card was the VDM-1 card, as in the Sol-20 by
Processor Technology. I have one of those cards in my IMSAI. 16x64,
and takes up 1 K of memory. I've seen boots that involve a VDM-1, and
one 2708 (1K EPROM) that leaves 62K for RAM, and uses the VDM-1 memory
for stack during boot, IIRC. Ugly, but it works. VDM-1 cards require
S-100 bus, or massive hacking. That makes them, probably, outside the
parameters of the "quickest and cheapest" setup you've set.
Peace,
Warren E. Wolfe
wizard at voyager.net
Right. That much I get... so once CP/M is running,
it's ordinary not
to refer to the boot ROMs? There's typically not a requirement to
keep some low-level BIOSy stuff in ROM?
No, there is no requirement to keep ANY ROM available after boot.
It is preferable, in most cases, to have the entire address space made
up of RAM once the system is actually running, as opposed to booting.
Some cases involve copying the ROM contents to RAM during boot, and then
disabling ROM. Again, as has been implied, EVERYBODY chose their own
method -- some were better than others, naturally enough. As a matter
of fact, for those systems which implement ROM at 0000 for booting, the
ROM *MUST* be disabled for any even half-way normal CP/M system to run.
(See the previous discussions on CP/M for Radio Shack Models)
Right. I know that there are *many* CP/M hardware
configurations; I
am trying to get down the nub of as minimal a hardware design as
possible.
CPU, 64k RAM, disk(ette) controller, ROM able to be disabled (could
be on controller), serial port. Anything else is gravy.
Sure. For the minimal system I have in mind, I'm
planning on a VT100
or some modern machine running a terminal emulator (Kermit, et al.) to
handle screen formatting.
Perfect.
A video card
will chew up valuable RAM, and many of them are only 16x64,
but it does let you do real-time screen updates, games etc.
Ah... now we are onto something - games... are there many games for
CP/M that require a video card, or were most happy with whatever sort
of TTY-type device (ANSI codes or not) was out there?