Re (2): [Oberon] http://www.oberon.ethz.ch/display.html

[Lisias Toledo]

peter_easthope at gulfnet.sd64.bc.ca wrote:

> Seems that
> SwitchTrident9xxx might involve the
> double buffering described in one of
> the tutorials, ... but how exactly.

Yes and no. To tell you the true, these ports deals with memory
segmentation.

All the memory of a vga card must fit (or used to fit, as I said
there're some time since I played with this) in a 64K memory segment at
$A0000 (real mode address).

Well, vgacards with 512k, 1024 and even 4096 was common, so what can be
done?

Memory banking... You use that $A0000 address as a "window" to the video
memory. Each "piece" of the framebuffer is called a "bank".

On tridents, we can choose the bank we want to read and the bank we want
to write. Since the Oberon video drivers doesn't need this feature, it
sets both to the same bank.

You can find tech details to Trident chips here:

http://www.plasma-online.de/english/help/solutions/trident_prog.html

p.s.: 
Do you have a old Trident GUI 9XXX?

This is low level programming, and one needs a lot of backgroud to
understand all the thing. We are dealing directly to the hardware here.
A step lower and we will end up talking about Assembly.

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