Complete BIOS Tuning Guide - "Spread Spectrum Control"



Spread Spectrum Control

Spread spectrum controls are really added to motherboards for one purpose only - they are sometimes needed so that a device for sale within the US can include a legitimate Declaration of Conformity stating compliance with Part 15 of the Federal Communications Commission (FCC) Rules. This stipulates that operation of the device (motherboard), (a) may not cause harmful interference, and (b) must accept any interference received, including interference that may cause undesired operation. Sales of electronic devices within the US require the strict observation of all FCC rules and regulations.

As a general requirement, every motherboard must be capable of generating and distributing more than one common clocking signal used to coordinate latching times as needed for the transfer and receipt of data across the many high-speed interfaces found in today's systems. Because it is uncommon for different busses to share similar operating frequencies, and because each must be kept independent of the others, a significant portion of motherboard resources are spent locating, monitoring, and regulating these circuits. Each circuit must include a reference frequency, or known base frequency, from which all other frequencies can be derived. A local oscillator usual provides this functionality.

The problem is these oscillators can sometimes cause electromagnetic interference (EMI) centered about their operating frequencies. In an effort to prevent these types of undesired interferences the FCC, an independent licensing organization for devices capable of transmitting electromagnetic signals, either intended or otherwise, operating under the purview of the US government, enacted "Rule 15," effectively limiting the output power of such devices.

Engineers, looking for a way to meet regulation, began using a method for limiting such interferences called spread spectrum clocking. Spread spectrum clocking causes the signal regulation circuit to slightly vary the frequency about the target frequency, effectively "spreading" the power over a somewhat larger frequency band. The method of operation can be used to control system output power below the FCC standard limits, allowing for a claim of full compliance.

As you can imagine, even the smallest variation in a clocking signal can be enough to create data transfer errors. The fundamentals of overclocking demand the cleanest, purest signal possible, which is why spread spectrum should always be disabled unless you have a good reason to enable it. Ergo, CPU Spread Spectrum, PCIE Spread Spectrum, MCP PCIE Spread Spectrum, SATA Spread Spectrum, and LDT Spread Spectrum should all be set to Disabled.

Complete BIOS Tuning Guide - "CPU Configuration" Final Thoughts and Recommendations
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  • takumsawsherman - Saturday, April 12, 2008 - link

    But for $400, you only get Firewire 400. Is that like a key, or something? If we pay $800 for a board, will they finally feel as though they can afford to add Firewire800, as Gigabyte did on their $200 boards like 3 or 4 years ago?

    When they talk about adding firewire itself to a board, does it never occur to them that a faster variation has existed for 5 or 6 years now? How insulting.
    Reply
  • Grandpa - Saturday, April 12, 2008 - link

    It doesn't matter what the price, performance, make, or model. If the board is unstable I don't want it! I had an Abit board once with a VIA chipset. It corrupted data when large files were transferred between drives. Several BIOS updates later, with the performance down to a crawl, it still corrupted data. Because of that ugly bad memory, stability is number one important for me. So this review is very relevant to others like myself. Reply
  • Super Nade - Friday, April 11, 2008 - link

    As far as I know, the capacitors you mention are made by Fujitsu's Media division (FP-Cap series), not Fairchild semiconductor. Fujitsu did try to gobble up Fairchild in the 80's, but the US government killed the deal. Apart from this, I am not aware of any connection between these two companies.

    Here is the link--> http://jp.fujitsu.com/group/fmd/en/services/capaci...">http://jp.fujitsu.com/group/fmd/en/services/capaci...

    S-N
    Reply
  • Stele - Saturday, April 12, 2008 - link

    Super Nade's right. The vendor marking on the capacitors - which have been the same for almost all such solid electrolytic polymer caps used on Asus boards for some time now - is very much that of Fujitsu: a letter 'F' in Courier-esque font between two horizontal lines.

    Interestingly - and confusingly - however, once upon a time this logo was indeed that of Fairchild Semiconductor... the deal that almost happened in the 80s may have something to do with Fujitsu's current use of the said logo. Either way, Faichild Semi have long since changed to their current logo (a stylised italic 'f') so today, any current/new electronic/semiconductor component carrying the F-between-bars logo is almost certainly a Fujitsu product.
    Reply
  • jojo29 - Friday, April 11, 2008 - link

    Just wondering how the Anandtech's Choice P5E3 Premium ( which i plan on buying) stacks up against this Striker? Any comments? Or did i miss something in the aricle as i was only able to skim through it, as im at work atm, and dontcoughwantcoughtogetcaughtbymybosscough... Reply
  • kjboughton - Friday, April 11, 2008 - link

    We used one X48 motherboard in this review and it was the ASUS P5E3 Premium. Enjoy the full read when you make it home. ;) Reply
  • ImmortalZ - Friday, April 11, 2008 - link

    You mention that overclocking the PCI-E bus provided tangible performance benefits on the EVGA board.

    Did you read about the rumblings around the net about some G92 based cards overclocking their GPU with the PCI-E bus? There are supposedly two clock sources for these type of cards - one on board and the other slaved to the PCI-E bus.

    Are you sure that the performance improvement is not because of this anomaly?
    Reply
  • CrystalBay - Friday, April 11, 2008 - link

    Hi Kris, while UT3 does scale very well with multi-core. The game it self has no DX10 support as of yet. Hopefully EPIC will will enable it in a future update... Reply
  • Glenn - Friday, April 11, 2008 - link

    All the benchies and comparisons are great, but how does it compare to a P35 board? A 965 or X38 board? I doubt you will convert those that already own an X48 and I (P35) have no point of reference within this article to see if I'm 5, 10 or 25% behind the preformance curve? Reply
  • Rolphus - Friday, April 11, 2008 - link

    Interesting review... only one question though. Why use the 32-bit version of Crysis on Vista x64? Is there an issue with the 64-bit version that I don't know about? Reply

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