For the most part, the North Bridge of the KM133 is very similar to the KT133 - it is even pin-compatible. The memory controller is the same, meaning 66/100/133MHz asynchronous memory busses are supported (using SDR memory, of course). Furthermore, an external AGP 4x slot is provided for those who find themselves desiring a more powerful graphics solution.

Of course, the main departure from VIA's KT133 is the integrated graphics offered on the KM133 part. While the graphics are referred to as ProSavage4, it should be noted that it is the 3D pipeline that has been derived from the Savage4. 2D has been carried over from the Savage 2000, which improved upon the often-chastised 2D of S3's previous generation. Thus, the KM133 includes a 300MHz RAMDAC, which offers support for up to 1920x1440x16 utilizing a 32MB shared buffer. Using this combination, VIA was able to incorporate acceptable 2D and still have a 3D chip that didn't require an oversized heatsink or a fan.

We found the clock speed of the core to be 120MHz, but even if a faster core was used, it wouldn't aide performance since memory bandwidth would serve as the limiting factor. Unfortunately, all of the devices with access to SDRAM must share the available bandwidth (1.06GB/s). Between now and the release of KM266 sometime in the second quarter of 2001, it won't really matter what 3D processor is used, so long as 133MHz SDRAM is retarding performance. Once KM266 enters the scene however, we may see the Savage4 core limit the 3D potential, as the chipset will have access to 2.1GB/s of bandwidth with DDR memory.

On the bright side, VIA's latest line of integrated chipsets offer support for S3TC texture compression and 2Kx2K sized textures for extra detail in supporting applications.

Included in the integrated package are S3's video acceleration features, which include up/down scaling algorithms and a motion compensation engine. As a quality addition, the KM133 also supports alpha subpicture-blending acceleration in hardware. S3 has traditionally excelled in video scaling, however, their motion compensation engine and a lack of iDCT leave the KM133 lacking in the video acceleration department.

Well, maybe not any Southbridge - the VT8365 can be mated to either the 686A or the recently released 686B Southbridge. We'd imagine that the 686A will be used as a cost saving measure, however, manufacturers wishing to add ATA-100 support to their list of features will likely opt for the 686B. Either way, both Southbridges allow the addition of an AC'97 codec, barring the need for an add-on soundcard.

Additional features shared by both parts include dual USB root hubs for a total of four supported devices. The 686A utilizes the ATA-66 protocol, while the 686B raises the bar to ATA-100.