Clock-circuit manufacturer International Microcircuits Inc. (IMI) claims to have addressed the system bus/memory bus mismatch in the forthcoming "Solano," or Intel 815, chipset.
IMI's C98xx family of clock generators walks a fine line, from both a technical and marketing standpoint. The chips allow motherboard designers to compensate for the mismatch between the Solano's 133-MHz system bus and 100-MHz memory bus. Meanwhile, built-in tolerances in the chip are being targeted both at OEMs and the rogue community of microprocessor overclockers.
The 11-member C98xx family includes eight chips for desktop PCs and three for mobile platforms. They support varying numbers of DIMMs and PCI slots and different combinations of four features geared to allow OEMs the flexibility to design boards around the new chipsets: Dial-a-dB, Dial-a-Frequency, Dial-a-Skew, and Dial-a-Drive.
The clock chips drive the Intel 815's frontside processor bus and SDRAM interface, as well as the associated PCI bus, AGP bus, USB bus, and the low-pin-count, or IOAPIC, bus now used internally to replace the defunct ISA bus. Most of these can be directly or indirectly controlled via features within IMI's clock chips.
The Dial-a-Frequency feature, for example, can be used to set the frontside processor bus at any frequency, including the standard 66.66-, 100-, and 133.33-MHz speeds of the Intel 815. System designers can also dial in intermediary speeds, such as 106.42 MHz, to test system tolerances.
Users can also program the bus to run at higher speeds than the highest-rated 133-MHz frequency. The feature may prove attractive to overclockers, a small, dedicated community of hobbyists who push PC silicon to their limits and beyond. What they're doing is not illegal, as long as they do not resell the boards. "What end users do in the privacy of their homes is up to them," said a spokesman at Intel Corp., Santa Clara, Calif.
However, pushing the chip- set beyond its limits may void the associated warranty. Board makers have already designed-in some level of programmability using their own BIOS interfaces.
"It's a big product for overclockers," acknowledged Elie Ayache, director of marketing at IMI, Milpitas, Calif., who estimated at least 10% of the overall user base may have attempted to overclock their chips. "But it's designed for OEMs to reduce cost as much as possible."
IMI's additional features enable designers to further improve their motherboards. Dial-a-dB allows the chipset to vary the sweep of the clock rate, designed to minimize electromagnetic interference regulated by the Federal Communications Commission. Dial-a-Skew and Dial-a-Drive enable engineers to program SDRAM clock skew and drive to accommodate different motherboard trace lengths and DIMMs, respectively.
All of the devices are in full production. The eight desktop clock chips ship in SSOPs and cost $2.55 to $3.15, depending on the features included. The three mobile devices add a TSSOP option and only support small-outline DIMMs. They range in cost from $2.55 to $2.85.