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Re: Things ...

To: SMACKINLA@cc.curtin.edu.au (Pat Mackinlay)
Subject: Re: Things ...
Date: Sun, 27 Jun 93 23:50:42 PDT
In-reply-to: <01GZWX8I5RHOFUMLVJ@cc.curtin.edu.au>; from "Pat Mackinlay" at Jun 28, 93 2:20 pm
> >While the TI34010 doesn't allow direct access to the VRAM from the
> >R3000, it does give us everything else.  Unless we can get another
> 
> I don't think this is quite right. The R3k _will_ be able to access the 
> 34010's memory "directly" - through its host bus. In this mode of 
> operation, the host processor can write "through" the 34010 and access the 
> VRAM (and/or DRAM) attached to the 34010. This is how the host puts code 
> into the 34k's memory. It will also allow us to use the video memory as a 
> dumb framebuffer during the initial software stages. Yes, it _will_ be slow 
> (the host bus is only 16 bit), but see my further comments below.

Yeah, you can get access to any location in the 34k's address space
(including its own registers).  However, its not part of the R3k's
address space.  The 34k implements 4 locations in the r3k's address
space:  two are address registers, one is status, and the other is
data.  To copy a block of memory you place the start address in the
address register and then copy the data from/to the data register.
Doing a bitblt this way would be a pain, to say the least.

> Rather more personal preference than anything else: Don't you just _love_ 
> the idea of the X server running on its own CPU? It'd be the equivalent of 
> having your own X terminal on board <grin>. No, it probably won't compete 
> for speed with a well-designed framebuffer, but I think it's a very elegant 
> solution.

The 34010 will be around half the speed at doing bitblt's than the r3k;
the 34k can probably do other things faster (lines, circles) but they
don't matter.  As Pat says though, the 34k will take the load off the
r3k.

-- 
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Pyramid Technology                      Email:  caret@pyramid.com
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