What is PCIE spread spectrum clocking?

What is PCIE spread spectrum clocking?

Spread spectrum clocking is the process by which the system clock is dithered in a controlled manner so as to reduce peak energy content. SSC techniques are used so as to minimize Electromagnetic Interference (EMI) and/or pass Federal Communications Commission (FCC) requirements.

What is spread spectrum clock in BIOS?

Spread spectrum clocking works by continuously modulating the clock signal around a particular frequency. This “spreads out” the power output and “flattens” the spikes of signal waveform, keeping them below the FCC limit. The MCLK Spread Spectrum BIOS feature controls spread spectrum clocking of the memory bus.

What is clock spread spectrum?

Spread spectrum clocking is a technique where the clock frequency is modulated slightly to lower the peak energy generated by a clock. Spread spectrum clocking lowers clock-generated EMI from both the fundamental frequency and subsequent harmonics, thereby reducing the total system EMI.

What is spread spectrum PLL?

Spread spectrum technique is capable of reducing the harmonic frequency amplitude peaks by several dB. The IDT5P50902 accepts an input clock frequency from 20 MHz to 50 MHz and produces an output clock of the same frequency, with a modulation frequency of ICLK*27/20000.

Does PCIe have a clock?

The PCIe standard specifies a 100 MHz clock (Refclk) with at least ±300 ppm frequency stability for Gen 1, 2, 3 and 4, and at least ±100 ppm frequency stability for Gen 5, at both the transmitting and receiving devices.

Why is spread spectrum needed?

The main advantage of spread spectrum communication technique is to prevent “interference” whether it is intentional or unintentional. The signals modulated with these techniques are hard to interfere and cannot be jammed. These spread spectrum signals transmit at low power density and has a wide spread of signals.

What is the BCLK frequency?

As written here, BCLK is the base clock (set by default at 100 MHz) used to determine the frequency for the CPU, the FCLK, Uncore (Cache), and the MEMory.

What is the advantage of spread spectrum modulation?

The main advantage of spread spectrum communication technique is to prevent “interference” whether it is intentional or unintentional. The signals modulated with these techniques are hard to interfere and cannot be jammed. An intruder with no official access is never allowed to crack them.

What is PCIe clock request?

PCIe uses a source-synchronous model. The transmitter supplies the clock to the receiver by embedding the clock into the data stream. A Phase-Locked Loop (PLL) circuit in the receiver recovers the clock. Additionally, PCIe defines a 100 MHz reference clock (REFCLK) supplied by the system board.

Is there such a thing as spread spectrum clock generation?

Spread spectrum clock generation (SSCG) or “dithering” (modulating the clock frequency), has been around for a long while, even before the PC and printer manufacturers got on the bandwagon. There are also several ways to produce a dithered clock, using discrete logic or FPGAs.

Can a spread spectrum clock be used in PCI Express?

The PCI Express specification gives you the option of using a spread- spectrum clock (SSC). The main benefit of this option is the reduced risk of radiated emissions issues, but not all solutions are compliant.

How does a SYNC code work in a spread spectrum clock?

A special sync code was used to match up the initial hopping sequence. Figure 2 – Original patent drawing for a “Secret Communication System”. Note the two coded roller strips that switch in a bank of several capacitors, which cause the transmitted and received frequency to hop in sync.

What happens when you spread the frequency of a clock?

Spreading the clock frequency with a low frequency with a fixed or pseudo-random modulation (30 kHz, typically), such that the modulated signal is significantly wider than the resolution bandwidth of the measuring receiver or spectrum analyzer, effectively reduces the emissions from all signals synchronized with that clock oscillator.