Intel Corp’s Fred Pollack used the Microprocessor Forum to unveil a few details of the forthcoming Pentium Overdrive chip. The long-awaited processor is designed to upgrade 80486-based machines equipped with an Overdrive socket – giving them Pentium performance. The reason for the delays become apparent when Pollack described the problems that Intel had to overcome. In particular, the designers have to cope with the slow Intel 80486 bus and the fact that the new Pentium technology is 3.3V whereas the old 80486 motherboards use 5V. Faced with these problems, Intel has taken the standard 90MHz-100MHz Pentium processor and tweaked it substantially. To avoid burdening the 80486 bus, the company doubled the amount of on-board cache, it has also increased the core:bus clock ratio to 5:2. So a 33MHz machine will have the Pentium running at 83MHz. To cope with the voltage problems the company has had to include a custom linear voltage regulator in the package. The extra cache helps to contribute to a die size 25% bigger than the regular Pentiums. The voltage regulation and the high-speed core means it runs hot… so Intel has glued a fan to the top. Not any old fan, Pollack advises; this is a high reliability part with a failure rate of less than 1% in 10 years. And if the fan fails? No you won’t have a molten blob in the middle of your office desk – you will just have a rather slow personal computer: the processor will enter a power reduction mode with the core:bus ratio reduced to 1:1.
