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PC motherboard clock supports multiple processors and chipsets

SAN JOSE, Calif.— Cypress Semiconductor Corp. has developed a universal clock generator that supports processors and chipsets from multiple vendors, including Intel, AMD, VIA and Silicon Integrated Systems (SiS), simplifying inventory requirements for motherboard makers.

The CY28551 PC motherboard clock is being touted as the industry's first device that supports multiple processors, supplying timing signals for both Intel P4 and AMD K8 processors. It supports chipsets from VIA, including the PT890, PT890 Pro, PM890, K8M890, K8T890Pro, K8T890, K8T900, and K8N890, as well as those from SiS, including the 656, 656 (FX, MX), 662, 756FX, 761GX, 770, 670, and 649MX.

“The big feature on this is the flexibility to be able to user-configure the clock to work with any of these different chipsets,” said Geoff Charubin, managing director of the PC Clock business unit. The user configures the clock as it's soldered on the board, eliminating the need for programmable circuitry which in turn helps cut costs.

Cypress designed the CY28551 under the guidance of ASUSTek Computer Inc., a manufacturer of motherboards and notebooks, based in Taiwan. Through pin selections on the CY28551, designers can select the required processor and chipset.

“I have counted about 12 devices this is replacing across the [chipset] platform. That's because [chipsets from] VIA and SiS have historically required a separate pin-out,” said Elie Ayache, marketing director for PC clocks at Cypress.

Motherboard manufacturers can simplify their inventory requirements, and can make adjustments to their product mix without the need for a different clock if a chipset or processor is in short supply. In addition, designers can transfer the same design and layout from one system to another using the hardware configurable CY28551, reducing risk and saving design time and resources.

“Customers in general consider the clock a critical device. It's a high-speed device and it requires meticulous layout and careful consideration of the signal and in the layout and in the design. Impedance matching is important for the stability of the system. Once they use this device on one platform and they do their meticulous layout, on the next design, all they have to do is port the same thing they did. It is minimum work and requires fewer resources,” Ayache said.

The CY28551 supports PCI Express-based chipsets, Ayache said. The convergence in clock architectures supporting multiple chipsets and platforms is being driven by the PCI Express standard, he added.

“Not only does this device support all of these chipset and platforms, but includes the features that allow the customers to take their boards into the channel business,” Ayache said.

The CY28551 offers overclocking support for end-user modifications and a watchdog timer with system reset for auto-reboot. It also features easy configuration via hardware strapping; operates from a 3.3-V power supply; and includes low-power differential buffers for lower noise and better performance.

The universal clock is offered in a 64-pin QFN package (CY28551) and a 56-pin QFN (CY28551-3).

“It's less than half the board space used by the older TSSOPs or SSOPs. It's actually a thinner profile than the SSOP because you don't have the legs propping up off the board,” Charubin said. He also mentioned that the electrical and thermal characteristics of the QFN package enable the device to dissipate less heat.

“The reason it does that is because it's more optimized to work directly with the silicon itself. If you look at most silicon that people put in packages, they are usually square, which our clocks are. If you look at the package it looks more like a square, it's actually the QFN. With that we're able to run shorter leads inside the package to connect it to the pins; therefore you get much better electrical characteristics and much lower heat dissipation,” Charubin said.

For specifications, link to the datasheet here: www.cypress.com/universal-clock-photo.

Pricing is less than $1 each in 10,000-unit quantities.

Cypress Semiconductor Corp., 1-408-943 2600, www.cypress.com

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