This new bus design is part of an ongoing effort to increase the speed at which data flows in other parts of the PC--not just the processor. The faster "system bus" is due in 1998, said sources close to the company.
The processor uses the system bus to talk to other components in a PC, and in some cases this becomes a severe bottleneck because the bus runs at a much slower speed than the processor. A 233-MHz Pentium processor, for instance, talks to the main memory at 66 MHz.
Intel is proposing to increase the bus speed of Pentium II systems to 100 MHz, sources said.
An enhanced bus is the latest bit of one-upmanship in the ongoing specs battle between Intel and Advanced Micro Devices (AMD). AMD has already said it will attempt a 100-MHz bus on the K6. Success, however, is by no means guaranteed for either company--the redesign pushes the physical limits of micro-architecture.
The system bus connects the processor to the computer's "chipset"-- a sort of Grand Central Station that in turn connects to main memory, peripheral devices (like printers), and other subsystems so that all of these elements can communicate.
Heavier computing demands have forced huge amounts of data traffic onto the system bus in recent years. Instead of making the system bus faster, Intel has come up with new architectures that create separate buses for the various subsystems within a PC.
For the Pentium II, Intel created a separate bus for the high-speed cache memory, which allows the specialized cache memory to speak directly to the processor. For graphics, Intel has created the Advanced Graphics Port (AGP). This will start to appear on new computers in the fall and will cut down on further system-bus traffic by giving graphics chips a dedicated, high-speed connection to the PC's chipset.
But despite these efforts to divert data traffic off the system bus, demands on the bus continue to grow. The bus has remained stuck at 66 MHz for close to three years, mostly because of a host of electronic signal problems that can arise if the bus speed is increased, said C.B. Lee, an analyst with Sutro & Co.
A wider bus also tempts vendors to find ways to take advantage of it, which means even further traffic. "You're running into physics problems," said Lee. "At 75 MHz, it's tough. AMD has tried this before."
Undaunted, AMD has said it will develop a 100-MHz bus for the upcoming 300-MHz K6 processors. Sources have also said that AMD will add a second, independent bus for the level 2 cache, similar to what Intel has done with the Pentium II. AMD will also adopt AGP, by the way.
An Intel spokesperson would not confirm specifications on a new Pentium II system bus but said Intel plans on releasing a chipset with an expanded bus. "We are working on taking that forward," he said. "There are physics issues you need to deal with, so the thinking is, 'Let's make it as substantial as possible."
Intel said the new bus would not appear in 1997. Roger Kay, an analyst with International Data Corporation, said it was likely a 1998 event. Sources at Intel confirmed this.