Re: Request a discrete refresh circuit schematic

[heuser.marcus@freenet.de]

Bryan Parkoff wrote:
> <heuser.marcus@freenet.de> wrote in message
> >
> > The addressing of the video memory isn't that bad, IMHO.
> > For anything speedy you need an address table anyway and it does not
> > matter what addresses are in it.
> >
> > Or do you really want a (slow) multiply by 40 for each line?
> >
> > In any case you actually *have* lines with 40 bytes in the standard
> > hires graphics mode - which can't be said of other popular computers of
> > the time *cough* C64 *cough*...
> >
> > The color generation and its effect of the video memory organization
> > (two bytes to form seven pixels, the color bit etc.) is an entirely
> > different case but AFAIK completely independent of the memory refresh.
> > But you can do a lot with masks and tables, too.
> >
> > The 8-bit Ataris for example have cleaner video modes (linear video
> > memory, "better" color generation via color palette registers) but they
> > are not necessarily faster when doing the same type of hires graphics
> > and certain things are even beyond them.
> >
>
>     It is clear that Apple II's TEXT/LORES and HIRES/DHIRES are not linear
> memory for saving memory reason,

I don't see how non-linear video memory actually saves memory. AFAIK it
saves address decoding circuitry.
In fact the opposite is true with the Apple architecture: The memory
holes in the video memory are wasted memory (at least for video
generation) *because* of the addressing scheme. IMHO this is the only
valid reason to bash Woz for the addressing logic  ;-)

> but Apple IIgs' super high resolution is linear memory in bank $E0/$E1.  Correct?

>From what I know this is true.

But it would've helped tremendously if the GS would've been clocked
faster for this fourfold increase in video memory - from a game
programmers perspective the linearity doesn't really help here.

On the other hand its palette registers and color generation without
artifacting are of course much better from a technological standpoint.

bye
Marcus