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 VIA KT133.Whilst VIA attacked the Intel compatible market with the Apollo Pro133A it also had to regain its presence in the AMD compatible market after not releasing a chipset at the launch of the Athlon processor. VIA entered the Slot A market in early 2000 with its KX133 chipset. This though was not the best timing for VIA as AMD intended to migrate its Slot A based Athlon processor over to a Socketed design by Q3 of that year. At the same time AMD modified the basic transmission protocol over the EV6 bus for the Athlon meaning that VIA had to modify its KX133 chipset. As a result VIA released its KT133 chipset for Socket A Athlon and Duron processors in the summer of 2000. Like the KX133, the KT133 quickly gained a reputation for being a fast and stable chipset amongst the PC hardware community with a number of good boards appearing shortly after its release. AMD also had much riding on the success of the KT133 chipset as summer 2000 saw the company begin to move rapidly away from the K6-2 and over towards it K7 based processor which by the comprised the Athlon and Duron chip ranges. An early delay of the KT133 left AMD with some early worries concerning the KT133, but these were allayed once the chipset reached the market as it coupled convincing performance to good stability. Chipset Design.Like VIA’s other chipset offerings, the KT133 can be described as being a “classic” chipset design being based upon a North and South Bridge layout which uses the PCI bus as the main connection between the two chips. Essentially the KT133 is a similar design to the Apollo Pro133A, but VIA removed the GTL+ bus interface and replaced it with the Alpha EV6 bus as used by the AMD Athlon family of processors. This is probably the biggest difference between the Pro133A and the KT133 as the EV6 bus is more advanced than its GTL+ counterpart. Unlike the GTL+ the EV6 can read and write from the CPU to chipset at the same time by using two 100 MHz channels, essentially making it a DDR (Double Data Rate) chipset. Both of these 100 MHz channels gives the EV6 an equivalent performance of a 200 MHz SDR (Single Data Rate) bus such as the GTL+. The use of a DDR bus such as the EV6 helps to increase the bandwidth between the CPU and North Bridge controller. As both the Athlon and Duron run on a 200 MHz Front Side Bus (before Dec 2000), VIA did not need to implement a range of bus speeds needed on the Apollo Pro133A. The memory controller on the KT133 is similar to that on the Apollo Pro133A as it gives usersthe ability to clock the memory bus at a different speed to that of the main CPU bus. Users of the KT133 can for example run a 100 MHz FSB Athlon (200 MHz DDR) with memory clocked to 133 MHz to gain full advantage of PC-133 SDRAM, or usets could still use any existing PC-100 SDRAM with the same 100 MHz bus Athlon (200 MHz DDR). 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. Like the Apollo Pro133A the KT133 uses the same South Bridge controllers in the form of 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.
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