15 Mar
2006
15 Mar
'06
3:37 p.m.
On 3/15/2006 at 5:12 PM Jim Leonard wrote:
To get around this, you write to CGA RAM while the beam
is *not*
drawing, but retracing horizontally or vertically back to the next
scanline or display cycle. You can transfer about 250 words during a
vertical retrace and exactly one word during horizontal retrace, so
that's 450 words per frame, so a snow-less full-screen update would take
3 frames (20fps).
The obvious goal is to not be in the position of having to update the
*entire* screen.
Maybe cheating a little, but:
Alternatively, you can install an EGA card running in CGA compatibility
mode. You can even double-buffer the thing (write to one bank while
displaying the other).
Cheers,
Chuck