21 Dec
2005
21 Dec
'05
4:22 a.m.
On 12/20/2005 at 9:07 PM Jim Leonard wrote:
(I say that and, looking at my CGA card in graphics
mode, there are
single-bit errors twitching on and off -- RAM tests okay so I guess the
ramdac has
blown a gasket somewhere)
Ramdac? I The output of the CGA was plain RGBI digital, buffered through an
LS244. There is a composite output, but it's sort of a simple-minded
resistor adder network fet to the base of a 2n3904 to so some level
shifting. Best recheck your RAM--and remember that writes to display
memory on a CGA can occur only during the retrace interval or they produce
"snow".
Cheers,
Chuck