Videologic Neon 250

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VideoLogicPrice – £120-130

System Requirements

  P133 or equivalent

  32Mb RAM

What Is PowerVR?

Before I jump into the review, I’m just going to recap on the
history of PowerVR technology.

Most modern 3D graphics cards draw all the triangles (polygons) in
a scene, and then pass them through the rendering pipeline in order
to texture them.

In doing this they perform a depth calculation (utilising the
z-buffer) that helps to reduce the number of triangles rendered by
the chip, by removing the triangles that cannot be seen.

Unfortunately if a triangle is partially visible, it cannot just
discard it. Instead it must be rendered as if it was totally
visible. This process of rendering polygons which are never seen is
called overdraw.

The PowerVR’s architecture works in a very different way, and in
fact thrives in a high overdraw environment. I hear you asking
“Why?”.

Simply put, the rendering engine on the Neon 250 only draws
polygons that are actually going to be seen on the screen.

It divides the screen into a series of smaller squares called
tiles, and then by a process of depth sorting, the tile is rendered
with only the pixels that are directly visible. The render engine
then passes on to the next tile.

Overdrawn

Q3Test running on a Neon 250

This process is
called deferred rendering, and thanks to the depth sorting
(which is done on the fly in hardware) there is no need for a
z-buffer.

As no z-buffer is needed, less memory bandwidth is required, or
alternatively the memory bandwidth available can be used more
efficiently – which is the case here.

Videologic have quoted a fill rate of between 200 and 500
MPixels/sec, which is not strictly true. The Neon 250 has a base
fill rate of just 125MPixels/sec, as it can render 1 pixel per
clock and with a clock speed of 125MHz this becomes the base fill
rate.

But as soon as you introduce overdraw in a scene, the “effective”
fill rate increases. So with an average overdraw of 2 the fill rate
is effectively 250MPixels/sec. If overdraw is an average of 4 then
fill rate effectively reaches 500MPixels/sec.

This may seem like a cheat, but it isn’t really bearing in mind
that any standard chip like a TNT2 will have to render a lot of
information that is never seen. In order to keep the framerate up,
cards like the TNT2 must increase their fill rate.

The Neon 250 on the other hand will only draw what is visible, and
with most games containing significant overdraw, it should have no
problem matching other chips on the market…

What You Get For Your Money

neon2501
Unreal Tournament running on a Neon 250

The card
is a relatively plain green board that features the PowerVR
series2 chip and four memory chips. And that’s it. Other than
a heatsink there is nothing more on the board, and it looks
rather unassuming when compared to the likes of a TNT2 Ultra
board.

Unlike a lot of other boards on the market there is also no TV-out
which is a shame, although in reality how many of us actually play
games on our TV? Admittedly there is the potential of playing DVDs
on the TV, but usually the TV-outs do not provide a picture that
can rival a dedicated decoder, whether it be a PC based one or a
stand-alone unit.

One interesting thing to note is that originally Videologic had
planned to market the Neon 250 with only 16Mb of SDRAM, but thanks
to the fluctuating memory prices they decided to go with a 32Mb
solution.

This doesn’t actually add too much of a performance increase, as
the memory is used more efficiently than with other designs, but at
least it allows for more texture storage which is always a plus.

Software

cardsb
The overdraw demo in action

On the software side,
Videologic have supplied a CD filled with not only the
essential drivers, but also some technology demos that show
off some of the more advanced features of the architecture.

One of the more impressive is the overdraw demo, which really shows
PowerVR coming into its own. Thankfully these can (in some cases)
be run on other hardware which allows you to see how the
performance of your old card matches up to the Neon 250.

Also on the CD is a selection of game demos that help show off the
card further. These include the memorable Incoming, the
not-quite-so-good-but visually impressive Klingon Honour Guard, the
oh-so-tedious Thief (well in my opinion anyway) [EDITOR – take that
man out and shoot him!] and the great-for-a-laugh Rollcage.

As I have said there are others, and these will all work very
nicely on the Neon 250, which means that should you own the full
versions of any of them you can expect some very nice fluid
graphics.

All in all the bundle is pretty good, and the supplied demos are
all fairly recent (which is a bit of a change) which helps make the
whole deal more attractive.

Quality Control

neon2502
More Unreal Tourney

Unfortunately everyone will
no doubt be more interested in how the card performs on
forthcoming titles like Quake III Arena and Unreal Tournament.

To this end I have included some shots of these games running on
the Neon 250 to show that it looks every bit as good as a TNT2
based card. You can find these scattered throughout the review,
with a few more on the last page.

The picture I have painted so far seems to be a very rosy one, and
certainly puts the Neon 250 in a good light. It is a good card, but
I wouldn’t be doing my job if I didn’t report on any issues that
affected the Neon 250. “What issues?” I hear you cry.

Due to its tile based nature, some graphical glitches do occur.
Some titles throw up problems for the Neon 250, and one of the more
important ones is Unreal Tournament.

Now from the screen shots (which were taken at 800x600x32) there
are no noticeable effects, but when the resolution is pushed to
1024×768 there are a few graphical glitches which, while they do
not affect the gameplay in any way, certainly detract from the
overall experience.

Conclusion

neon2503
DM_Morpheus from the Unreal Tournament demo, as seen on a Neon250

That said, the guys at VideoLogic are constantly working on
new drivers, and they have certainly come on a long way in both
quality and performance.

They are also working with the game developers in order to ensure
that patches will be created for existing titles, and that new
titles will have no problems.

At this price point the Neon 250 is a very competent card (as can
be seen from the benchmarks below), and certainly deserves
consideration if you are intending to purchase a new graphics card
and not spend the earth on it.

Benchmarks

Tests were done on the following system –

P2 450

Abit BX6 rev2.0 motherboard

128Mb RAM

9.1Gb Seagate Cheetah 10000rpm Ultra2 HDD

All drivers – latest downloadable versions

  Eye Candy  

Review

by Pete, Contributor

Source : Eurogamer

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