Preventing CGA revisionist history
ard at p850ug1.demon.co.uk
Wed Jan 18 11:08:27 CST 2006
> On 1/18/2006 at 12:13 PM mbbrutman-cctalk at brutman.com wrote:
> >If you look at IBM documentation (especially the BASIC manuals from the
> >era) it is clearly listed as Brown, not dark yellow.
> Looks like the network around Q204/Q205 is the dark-yellow to brown
> translation in the IBM CGA montor. I can scan that part of the circuit and
> post it if anyone's interested.
I wonder if we're looking at different schematics. In mine, Q204 and Q205
form the buffer stage for the Hsync signal. The emitter of Q205 seems to
be a blanking signal. the collector feeds sync to Q402 (the deflection
In mine, Q206 is the 'brwon kludge' I think.
> I haven't checked, but wasn't there also special-casing in the EGA BIOS
> code to handle the dark yellow=brown case?
I doubt it. I seem to rememebr a PROM in the input stages of the 5154
monitor, which may well have done the same conversion, though.
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