Spread Spectrum Clock Generation (SSCG) is an efficient approach to reducing electro-magnetic interference emissions in many high-speed digital systems including hard disk drives. That’s because it increases the size, weight and cost of the system.
What is clock spread spectrum?
Spread spectrum clocking (SSC) is a special way to reduce the radiated emissions of digital clock signals. SSC is the variation of the frequency of a clock signal in a controlled way. In the frequency domain, the SSC reduces the peak amplitude of a digital clock signal by shifting the frequency.
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 SATA spread spectrum?
This BIOS feature controls spread spectrum clocking of the Serial ATA (SATA) interface. When set to Down Spread, the motherboard modulates the Serial ATA interface’s clock signal downwards by a small amount. Because the clock signal is modulated downwards, there is a slight reduction in performance.
What is 1.5gb PHY?
PHY stands for “physical layer”. By jumpering pins 5 & 6 will cause the drive to go into a legacy 1.5 Gbit/s mode, rather than its default 3.0 Gbit/s mode.
Should I disable spread spectrum?
Generally, frequency modulation through spread spectrum clocking should not cause any problems. Therefore, it is recommended that you disable the MCLK Spread Spectrum feature if you are overclocking the memory bus. You will be able to achieve better overclockability, at the expense of higher EMI.
Why spread spectrum is required?
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 need of spread spectrum?
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.
Should I disable Spread Spectrum?
What is VRM spread spectrum?
The VRM spread spectrum frequency-modulation reduces EMI, noises, and ripples effects by spreading their frequencies over a wider bandwidth. It also improves efficiency compared to constant switching frequency modulation techniques, with a tremendous decrease in total losses.
What is HDD PHY?
A physical drive is a term for the hard disk drive unit or hardware within a computer, laptop or server. It is the primary storage hardware/component within a computing device, and it’s used to store, retrieve and organize data.
In theory, spread-spectrum clocking means that the tone is varied so that the clock signal varies continuously around the desired frequency. For example, for a 1 GHz processor, the frequency might be 999.5 Mhz at one moment in time and 1.0005 GHz at another.
Why to use a spread-spectrum clock in PCIe?
Using a spread-spectrum clock in a PCIe spec helps reduce the risk of radiated emissions issues. However, not all solutions are compliant. One of the main drawbacks of spread-spectrum clock (SSC) would be the need for a system with a common reference clock (Refclk) architecture, in which everyone gets a copy with skew of less than 12ns.
What is spread spectrum modulation?
In telecommunications, direct-sequence spread spectrum (DSSS) is a spread spectrum modulation technique used to reduce overall signal interference. The spreading of this signal makes the resulting wideband channel more noisy, allowing for greater resistance to unintentional and intentional interference.
