VIA Apollo Pro133A.

Now the oldest of the four chipsets in this comparison, the VIA Apollo Pro133A was released in early 2000. At the time its main rival (from Intel’s perspective) was the unpopular Rambus compatible i820. As expected the Apollo Pro133A offered a considerable price/performance advantage over the i820. The biggest problem for the Apollo Pro133A was that at the time of release, the venerable Intel i440BX chipset still offered superior memory performance in comparison.

Nonetheless the Apollo Pro133A has been a hugely important chipset to VIA for a number of reasons. When it was released in early 2000, VIA was still plagued by a reputation for making unstable and incompatible chipsets typified by the Super 7 MVP3 of 1998. If its aim of becoming a major chipset manufacturer was to be achieved, VIA needed to release a chipset which was stable and reliable. VIA built the Apollo Pro133A upon a design which it had matured throughout 1998 and 1999 in the form of its Apollo Pro and Apollo Pro133 chipsets and by the time of the release of the Apollo Pro133A, VIA had managed to iron out many of the bugs.

VIA also had a reputation of building chipsets which offered inferior performance in comparison to their Intel counterparts. As will be seen later in this article, the Apollo Pro133A went some of the way to addressing this problem, it was one area where it was still found wanting.

Most importantly for VIA was the timing of the release of the Apollo Pro133A in that it was a chipset which met the needs of the market. Late 1999 saw Intel try to steer the market in a new direction towards Rambus RDRAM with its i820 chipset. Unfortunately for Intel Rambus RDRAM proved to be extremely expensive in comparison to PC-100 and the then new PC-133 SDRAM whilst offering no comparable performance advantage. Apart from the high-end i820, Intel only offered the ageing i440BX and low-end integrated chipsets in the form of the i810 family. Thus a golden opportunity was handed to VIA by the market, design and sell a high-end PC-133 SDRAM compatible chipset for the FC-PGA Pentium III which offered features such as AGP 4X and Ultra DMA 66.

Chipset design.

Unlike Intel’s i820, VIA did not adopt a revolutionary new design for the Apollo Pro133A, instead choosing to build upon existing designs from the firms P6 compatible chipset family, the Apollo Pro. Essentially an enhancement of 1999's Apollo Pro133, the Apollo Pro133A is based upon the classic chipset layout of North and South Bridge controllers.

The North Bridge, designated VT82C694X handles the CPU interface via Intel’s GTL+ architecture which can be run at speeds of up to 133 MHz. Like the CPU interface, the memory interface for the Apollo Pro133A can run at 133 MHz offering increased bandwidth over earlier memory standards such as PC-66 and PC-100. The main North Bridge feature which was brought in for the Pro133A was the inclusion of AGP 4X. As the name alludes to, AGP 4X allows for data transfers over the AGP bus at up to 4X its clock speed (defaulted to 66 MHz).

One of the most interesting features of the Apollo Pro family of chipsets is the ability to clock the memory bus at a different speed to that of the main CPU bus. Users of the Apollo Pro133A can for example run a 100 MHz FSB Pentium III with memory clocked to 133 MHz to gain full advantage of PC-133 SDRAM. Similarly users of 66 MHz FSB Celeron processors can set the memory bus to 100 MHz (where the BIOS permits this) in order to gain maximum advantage. The only downside of this feature is that it increases the time taken by the memory controller on the chipset to read and write from main memory.

The Apollo Pro133A supported 168 pin DIMM modules featuring PC-66, PC-100, PC-133 SDRAM, EDO DRAM and VC SDRAM (Virtual Channel SDRAM). The Apollo Pro133A does though allow for a maximum 2GB of PC-100 SDRAM to fitted which is an impressive memory capacity.

As the Apollo Pro133A has been in existence for nearly 18 months, it has been paired with two different SouthBridge controllers. The first controller that it was used with was the VT82C686A which included support for U/DMA 66. The 686A also featured support for integrated hardware monitoring as well as AC 97 integrated sound.

Late 2000 saw the 686A replaced by the VT82C686B which added support for U/DMA 100 Hard Drives on top of the existing support for U/DMA 33 and 66 drives.

Introduction.

VIA Apollo Pro133A page 2.