[Fwd: Re: [Open-graphics] Trading off time and space]
prefect_ at gmx.net
Mon Dec 6 16:52:23 EST 2004
On Monday 06 December 2004 13:45, nico at seul.org wrote:
> > Anyway, I'd still be very interested in comparing gate count for current
> existing graphics cards to what the FPGA can offer. According to
> http://www.hwhunpage.hu/gvt_e.htm, a very modest TNT2 chip takes 8
> million transistors. It would seem like a good starting point if we can
> fit that onto the FPGA. Anyone have some good numbers of how this maps?
Always keep in mind that the TNT2 has two complete texture units in hardware
(at least as far as I know). This includes all the logic for mipmap
selection and for filtering, which is quite expensive especially in terms
of multipliers etc.
It might be a valuable feature-and-space-vs.-performance tradeoff to reuse a
single texture unit for multiple textures (by loading different memory
offsets and texture specifications) when multi-texturing is needed. This is
bound to buy a *lot* in terms of flexibility (how else would you put enough
texture units for interesting shader work onto the chip?), and maybe it's
even possible to do this without hurting the single-texturing case (which
is important for desktop work).
As always, I'm not sure if this is realistic, since I'm not a hardware
person. I just wanted to point out that we're in no way forced to follow
the same design decision as NVidia back then. There are many creative ways
in which the transistor/gate/whatever budget can be used.
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