100MHz Bus Speed & Socket-7 Motherboardsby Anand Lal Shimpi on September 27, 1997 6:46 PM EST
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In May of 1997, when Intel finally released the true successor to the Pentium Processor (the Pentium MMX was simply an enhanced Pentium in my mind), the Pentium II, it became quite obvious what sort of a limiting factor our friendly 66MHz bus speed turned out to be. The actual clock speed of a CPU is derived not by a simple game of point and choose, but by an even more simple equation: CPU Clock Speed = Bus Speed x Clock Multiplier. The Pentium II, starting at 233MHz at its release and now up to speeds in excess of 300MHz required that a clock multiplier of at least 3.5x be used in cooperation with the 66MHz bus to obtain the high clock speeds the processors ran at. The 300MHz Pentium II operating at a 66MHz bus speed requires a 4.5x clock multiplier, and with Intel planning a 400MHz Pentium II later in 1998 and eventually Pentium II processors in excess of 500MHz maintaining this silly bus speed would eventually pose quite a few engineering problems to motherboard manufacturers. The solution? Increase the bus speed. But to what speed? 75 and 83.3MHz are nice for overclocking, but if you're going to make a major change such as this one you go for the gold, the mighty 1-0-0.
A Discriminating Speed Limit: 66/100
To the surprise of all of their critics, Intel made a huge jump in their specification for the Bus Speed of the next generation of Pentium II processors, from 66MHz to a whopping 100MHz. However with all the hype surrounding this decision, they failed to explain what would happen to the hundreds of thousands of Socket-7 motherboard/processor owners; would they be left in the dark? Forever doomed by the 66MHz bus speed? Unfortunately, yes, from Intel's standpoint that is. Their position on this is very understandable, they have this hot new processor that they want the masses to buy, so what better way to promote it than supporting it with a bus speed never before achieved by a manufacturer in the PC industry? This way, Intel kills the Socket-7 market, and gains complete control of the Slot-1 Industry since they are currently the sole proprietors of the Slot-1 architecture (although that could change very soon).
The Catch? Three Letters
No plan is flawless, although Intel's marketing strategy seemed to be, there still remained a tiny glitch, Advanced Micro Devices, AMD for short. If Intel could pull off a 100MHz bus speed who is to say that AMD can't? No one, at least AMD didn't think so. Shortly after the announcement of their hit K6 Processor, AMD released the first specs of their next generation K6 chips, including the AMD K6-3D. What made the K6-3D so special was it included support for both the 66MHz bus speed, and the 100MHz bus speed while maintaining compatibility with the Socket-7 architecture. As Cyrix did with their 6x86-PR/200+ AMD managed to breathe more life into the Socket-7 market by announcing a processor that would be at home with a 100MHz bus speed. And as expected, the first few chipset manufacturers to announce compatibility with this bus speed were non-Intel chipset manufacturers, specifically VIA and ALi. Although everyone expected the industry giant VIA to produce a chipset with support for the 100MHz bus speed, no one would've guessed (well, most people didn't know at the time) that Acer Labs Incorporated (ALi) was working very closely with AMD to develop a chipset that would accent the release of the K6-3D with support for the 100MHz bus. When it was finally made public that ALi was working on a chipset design (Aladdin V) with 100MHz bus support, the race was on to get to 100MHz. VIA announced their MVP3, while SiS quietly worked on their 5591, soon enough we'll see quite a few chipsets which would support this speed...however even while benchmarks were floating around about how well the K6 performed with the ALi Aladdin V Chipset no one bothered to ask if Intel had changed their minds about supporting the 100MHz bus speed with their TX Chipset, the most popular Socket-7 chipset out today...