Re: Apple II 80 column Mode on Composite Monitor

[Roger Johnstone <roger@roger.geek.nz.removethisbit>]

In <EuudnRcB4sjSinrb4p2dnAA@telenor.com> Knut Roll-Lund  wrote:
> Michael J. Mahon wrote:

>> CGA is a 15kHz line rate, so there should be no sync problems.
>> 
>> However, the RGBI plus sync output of the Apple II RGB cards is
>> not fully compatible with the IBM standard, so a little adapter
>> will be required in most cases.  Search the web for more info.
> 
> I don't know about II/II+ RGB cards but:
> 
> The IIe RGB card does output a signal that can be converted into use 
> with a CGA monitor. First the typical CGA monitor requires there to be 
> a  separate vertical sync. The IIe RGB card outputs only composite 
> sync.  The vertical sync can be made with an LM1881 see: http://home.
> online.no/~kr-lund/A2E-CGA.htm
>
> Then the colors are wrong so one needs to swap them around a bit to 
> get  a passable picture. I did this with a GAL22V10.
>
> So I use a CGA monitor with my IIe and the IIe RGB card.

There are several different Apple II RGB cards from several different 
manufacturers, so all this discussion depends on which card you have. 
For example the Taxan Kaga card I had in my IIe had an analogue RGB 
output just like the IIGS, and at least one of the Applied Engineering 
RGB cards had outputs for both CGA and IIGS monitors.

-- 
* Roger Johnstone, Invercargill, New Zealand -> http://roger.geek.nz
* PS/2 Mouse Adapter for vintage Apple II or Mac
* SCART RGB video cable for Apple IIGS