eVGA GeForce4 MX440 review


Lightspeed Memory Architecture II

As you can guess by the name, this is an updated feature present on the previous GeForce 3 boards. LMA 1/2 both work to reduce memory bandwidth requirements, which will increase performance by reducing redundant processing. The ATI Radeon & PowerVR Kyro Graphics cards feature similarly themed technologies – reduce redundant processing, save bandwidth, improve performance. It does this in several ways:

Crossbar memory controller. Compared to the GeForce 4 Ti, the GeForce 4 MX uses 2 Crossbar memory controllers, as opposed to 4. This provides for a more efficient way of accessing the frame buffer as compared with traditional memory controllers. The net effect being that it optimises bandwidth use. No application support is required for this.

Loseless Z-Compression. The Z-Buffer contains depth information for every single pixel to be rendered by the Graphics card. Thus using higher resolutions not only consume more fill rate, they also require a larger Z-Buffer as more pixels will be rendered. The GeForce 4 does on-board hardware compression of Z-Buffer data. Most critically it is loseless, so there will be no precision loss which could adversely affect the image. According to NVIDIA this hardware compression will reduce the Z-Buffer requirements about 25%. Once again, this saves memory bandwidth. No application support is required for this.

Z-Occlusion Culling. Traditionally Graphics cards have performed a lot of redundant rendering by rendering pixels that will inevitably not be visible. This redundant rendering is known as overdraw. The level of overdraw can vary from title to title with some having an overdraw level of 3 or more, while others are much lower. Reportedly id Software game engines’ are excellent in this area. Though clearly with games getting more complex the level of overdraw is not about to decrease of it’s own accord. While many Developers have added in their own software methods to reduce overdraw others will need to rely on that provided in Graphics cards themselves, if any, e.g. PowerVR Kyro cards use a Tile-based deferred rendering system which is excellent at eliminating overdraw & are perhaps the most efficient consumer Graphics cards around.

The first part of this process is the Depth test - Z-Buffer values are compared to determine what is visible in a scene, i.e. pixels at the front of a scene will obscure pixels with a greater depth, i.e. behind them. For example, if your viewpoint is looking at a solid wall, then any pixels behind that wall won't be visible through it. As such any non-visible scene elements are completely disregarded, only visible elements get sent on to the Framebuffer.

The second is the Occlusion Query. This tests whether triangles are hidden completely behind other triangles. As before, non-visible triangles are disregarded & play no further part in the rendering process.

Z-Occlusion Culling, unlike the other LMA II features does however require Application support & will only work with Front to Back order rendering Titles.

Auto Pre-Charge. This minimizes the latency issues involved with accessing a different area of memory. No application support is required for this.

Fast Z-Clear. Fairly self-explanatory this one. This minimizes the amount of bandwidth & time needed to clear Z-Buffer data which will also improve performance further. No application support is required for this.

DVD / MPEG 2 decoding

The Graphics card comes bundled with the great PowerDVD XP (4.0), albeit limited to 2 Channel or S/PDIF Output. This is a fairly poor choice, as it happens the supplied PowerDVD 4.0 doesn’t support the MPEG decoding features of the GeForce 4 MX. When trying to play a DVD with Hardware acceleration enabled you’ll be greeted with the following non-descript error message.

Thankfully, there is a patch available to fix this though however take note because it’s not listed on eVGA’s website and wasn’t easy to find on Cyberlink’s website either, eventually I managed to locate it here This patch is designed for anyone who purchased PowerDVD XP 4.0 online before March 8, 2002 or anyone who received PowerDVD XP 4.0 bundled with their PC hardware. It provides support for the most recent devices on the market, such as ATI TwinView & NVIDIA NV17/NV 25 chips.

The GeForce 4 MX itself features NVIDIA’s VPE (Video Processing Engine) which provides Motion Compensation & iDCT (inverse Discrete Cosine Transform) support for hardware assisted MPEG decoding, which can greatly reduce CPU usage during DVD playback & such.

In most instances, very little are the changes between frames on DVD (MPEG2) movies. Using predictive coding it is possible to calculate/measure the motion of moving objects between frames, though. This data can then be used to predict their position in future frames. A supported software DVD decoder is required for this, though the bundled PowerDVD XP will provide you with this support once patched.

To test out the MPEG decoding features of the GeForce 4 MX I loaded up the newly patched PowerDVD XP and ran a 5 minute segment of “The Fast and the Furious”. Audio Output mode was set to S/PDIF Output as this would allow the SoundBlaster Audigy’s Driver to handle the AC-3 decoding, providing 5.1 output.

Hardware acceleration disabled

Hardware acceleration enabled

As you can see there’s not too much difference in CPU usage either way, though I’d guess this can also be scene dependent as well. For comparisons sake the 3D Blaster GeForce 3 Ti 200 which I had previously tested with in Pearl Harbor showed a much more noticeable reduction in CPU usage when Hardware Acceleration was enabled.


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