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On Fri, 2 Jul 1999, Shawn Hargreaves wrote:
> This doesn't make sense to me: in the 80x86 architecture, IO ports and
> memory are completely different things, so it is a nonsense to get a pointer
> to these.
> The IO port space is a 64k block of addresses that are accessed
> using special instructions, in parallel and on a different bus to normal
> memory. Some cards also have memory mapped IO registers, but that is a
> different thing.
...
> I suspect that this BeOS function is for non-Intel hardware, where the ISA
> or PCI port space might indeed end up being mapped as a special memory
> region.
>
This is what I knew, thats why it seemed strange to me, and would explain
why the function only returns 0x0000 on my Intel machine.
> > The thing is that the standard hooks are rather limited. There is a
> > screen->screen blit function, rectangle fill, invert, and line drawing,
> > but thats about it.
>
> That's all you get on most hardware in any case. The fills and vram blits
> are where the speed boost comes from.
That is what I thought after I wrote it, and realized the VBE/AF drivers
should be a low priority. screen->screen Blit is the most important
thing, and it is implemented.
> > Hmm, a wicked thought just accured to me. Would it be possible to mmap
> > the frame buffer, but also map it to a file?
>
> With the Linux fbcon driver, "cat /dev/fb0 > file" is a nice easy way to
> take a screenshot.
I love Unix!
> I think all of them need at least one extra block, and many use two or
> three. They use it for talking to memory mapped IO registers. Old cards use
> IO ports for everything, but with modern ones it is usually faster just to
> use the ports for the setup operations, and use memory registers for the
> actual drawing work. Some cards (eg. NVidia) don't even provide IO port
> versions of the accelerator registers.
This will be a challenge to implement if its possible. I could hack
around on this for hours ^_^ Unfortunately I don't have hours.
> --
> Shawn Hargreaves - shawn@xxxxxxxxxx - http://www.talula.demon.co.uk/
> "A binary is barely software: it's more like hardware on a floppy disk."
--
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