D'Arcy J.M. Cain wrote:
On Wed, 03 Mar 2010 14:42:00 +0000
MRAB <pyt...@mrabarnett.plus.com> wrote:
Gregory Ewing wrote:
Mk14 from Science of Cambridge, a kit with hex keypad and 7-segment
display, which I had to solder together, and also make my own power
supply. I had the extra RAM and the I/O chip, so that's 256B (including
the memory used by the monitor) + 256B additional RAM + 128B more in the
I/O chip.
In case some of you youngsters think that there is a typo in the above,
no, he means a total of 640 bytes. In today's terms that would be
approx 0.0000006GB.
Makes me want to go down to the basement and fire up the Altair. :-)
There was partial address decoding, so the blocks appeared at several
different places in the address space, the blocks weren't contiguous
(normal RAM at 0xFxx, extra at 0xBxx), and the external address bus was
12 bits.
Not only that, I discovered that one of the bits in the extra RAM
was faulty - stuck at 0 (or was it 1)?
But I was still able to play Nim and Duck Shoot (after keying it in)!
:-)
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