Re: Mega II Chip Information

["Bryan Parkoff" <nospam@nospam.com>]

<aiiadict@gmail.com> wrote in message 
1175227287.147177.237680@d57g2000hsg.googlegroups.com">news:1175227287.147177.237680@d57g2000hsg.googlegroups.com...
> On Mar 29, 7:34 pm, "Bryan Parkoff" <nos...@nospam.com> wrote:
>>     Please feedback what you think about Mega II chip.
>
> it's a neat chip.  It took ?years? to develop, and I imagine it is
> pretty complicated inside.
>
> ROM (characters) (or is this on the ROM chip of the GS?), video output
> (hgr, DHGR, text, GR, mixed modes), keyboard input, speaker output,
> joystick input, memory switch softswitches... etc.  (IWM too?)
>
> Why try to reverse engineer the Mega II when it is already done?  Look
> at the Apple IIe schematics and you'll see exactly what the Mega II
> does.

Rich,

    Well, Mega II chip has all Apple //e's functions, but it does not have 
schematic of RGB matrix.  RGB matrix is the DHGR pixel information from NTSC 
to RGB conversion to be used for HGR / DHGR.  I have enough information of 
schematic which Apple //e and Apple IIgs are nearly identical.
    I believe that ROM of Mega II chip has HGR, LGR, and TEXT ROM, but it 
needs second ROM.  First 8-bit data comes from HGR, LGR, & TEXT ROM.  Then 
8-bit data is used to go to another ROM to extract RGB matrix.  RGB matrix 
is the information of NTSC to RGB conversion.  It is what I am interested 
NTSC to RGB conversion.  It is necessary to deconstruct RGB matrix ROM to 
find this out.

Bryan Parkoff