Spread spectrum clocking
Under spread spectrum clocking , abbreviated SSC is in the synchronous digital technology , a special clock signal (Engl. Clock understood), the electromagnetic interference minimized. The clock signal is continuously varied in a certain frequency range, it is artificially provided with a so-called jitter .
background
A synchronous digital system is driven by a clock. This periodic clock signal usually has a very narrow frequency spectrum. The emitted energy is limited to a very small bandwidth . To reduce the risk of possible radio interference to reduce, by means of varying frequency spreading (engl. Spread Spectrum frequency) in a certain frequency band. In the case of a 1 GHz processor, for example, the clock generator is varied in the range between 999.5 and 1000.5 MHz.
The emitted and disruptive amount of energy remains the same, but is now distributed over a larger frequency range, and this reduces the disruptive power at a certain frequency.
Application in the computer field
In the computer area, SSC is implemented in the following components:
- Processors
- Mainboards (PCI-Express)
- Hard drives
- Disk controllers
- Flat screens
Possible problems
Activated SSC can lead to a variety of computer hardware problems. Especially in the case of SATA hard disks attached to SAS RAID controllers with SAS expander chips, the hard disks may not be recognized by the RAID controller.
Individual evidence
- ↑ Spread-Spectrum Clocking (National Instruments, Developer Zone)
- ↑ a b Leave spread spectrum clocking disabled (TechTarget, SearchWindowsServer)
- ↑ Application Note: Spread Spectrum Clocking - What is Spread Spectrum Clocking and why is it needed in Serial ATA implementation? (PDF; 199 kB)
- ↑ spread-spectrum clocking reception for displays ( EE Times Asia)
- ↑ Western Digital Raid Edition III HDDs are not recognized by the RAID controller (Thomas Krenn Wiki)
- ↑ Intel storage system SS4000-E: Hard disks, such as the Western Digital WD2500JS SATA, are not recognized. Why is that? (Intel Reseller Center)
- ↑ SSC Toggle Utility - Barracuda 7200.9 ( Memento of the original from April 29, 2010 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. (Seagate Knowledge Base)
Web links
- Datasheet CDCS501 example of SSC clock generator and buffer (Engl.)