Video cards using TurboCache

On Mon, 24 Oct 2005 07:57:33 -0500, Peabody
wrote:

A while back I got some excellent advice here about upgrading versus
getting a new system (still in the learning phase on that), and one
of the new-system suggestions included a low-end PCI-e video card
using something called TurboCache.

I believe I may have been the one that gave you that advise a few
months back, though things have changed somewhat in the past little
bit. If you're looking at a low-cost solution, then an nVidia
TurboCache design isn't a bad card, but now the cost advantage has
mostly evaporated. I'm now seeing regular GeForce 6200 cards selling
for only $10 more than 6200 TurboCache cards. Previously the
difference was most like $60 or $70.

Apparently this involves reducing the ram on the card to something
like 32MB, and using system ram for the rest of the "128MB" of video
ram. Apparently this is made possible by the high-speed
bi-directional transfers available through PCI-e 16x.

Yup, that's about it. The vast majority of the time your video card
is only using a rather small amount of memory (usually less than
16MB), so that can be stored in the on-board memory. When more memory
is needed the video card can swap in and out memory from the main
system memory. Pretty much the same concept as a processor's SRAM
cache, except that we're talking about larger but slower memory here.

But is this just deja vu all over again? Is this just "integrated
video" on a separate card?

Sort of yes, except that with integrated video you tended to use ONLY
main system memory. With TurboCache you're using MOSTLY memory on the
video card and only occasionally going to main memory when needed.

I thought that the big problem with
integrated video was not so much the use of the ram per se, but
rather the sharing of the memory bus, and the slowdown that
produced.

For most applications the "slowdown" is lost in the noise these days,
less than 1%. Where you really take a performance hit is in games,
and there the performance hit can be quite large.

However now that a regular GeForce 6200 costs only about $60-$70 while
the TurboCache ones are running at about $50-$60, the difference in
price is small enough that it's probably worth while spending the few
extra $$$'s for MUCH better 3D performance. In the future 3D
performance is likely to see more use outside of games and high-end
workstation applications, so this $10 is a small investment for the
future.

If that's right, how is a Turbocache card better than
something like an integrated ATI Radeon Express 200?

Well, at least it has 32MB on the card. So let me ask this. If no
gaming is involved, is the use of system ram unlikely to happen
often?

With 2D applications the use of system RAM would be quite rare.

Would playback of DivX, Xvid, MPEG-2, HD video require the
use of the system ram?

Probably not, or at least not often enough to make any difference that
could be measured by a benchmark, let alone any difference that you
would actually *feel*.

-------------
Tony Hill
hilla underscore 20 at yahoo dot ca