680i SLI FSB Straps - Overclock.net

DuckieHo · 05-23-07

http://it-review.net/index.php?optio...=1363&Itemid=1

Quote:

The picture we got from our test results looks pretty good except for the part between 1333 and 1456MHz. There is definitely something odd happening there. The board works at a same strap from 1067MHz to 1282MHz (lets call it STRAP0), then at 1284MHz the strap changes (lets call this strap STRAP1). The drop in performance is not that big, and is pretty much as expected. 1333MHz still works good, and that’s comforting since that is the FSB speed for the upcoming Intel processors, but after 1333MHz the board goes crazy. At 1338 MHz the board changes the strap once again but this time the drop in performance is really big (call this STRAP4). Then the board jumps between all three straps mentioned so far up to 1376MHz. We strongly advise you not to use to board in this range, but if you do stick to 1360MHz or 1368MHz, they work at STRAP0 and show really good performance. After 1376MHz the board stays in STRAP4 up to 1454MHz.

When you hit 1456MHz the board goes back to STRAP1 and stays in STRAP1 for quite a while. We noticed two FSB holes where the board wouldn’t post, you can see them as a lack of line in the graph. At 1920MHz the board changes the strap. The drop in performance is similar to one between STRAP0 and STRAP1. Call this strap STRAP2. The there is another strap change at 1978MHz to what we named STRAP3. Seems that the chipset is getting close to it’s maximum frequency at those speeds and starts to rapidly change straps. It might be a good idea not to cross the 1918MHz FSB when you overclock since that’s when you’ll lose some performance due to strap change. If you go back and take another look at our test results you’ll see that 1918 is the highest performing point for the memory. Taking a look at the graph once again shows us that the straps of 680i SLI behave as expected, with exception the 1338MHz to 1454MHz when the board behaves a bit crazy. We can’t say for sure why this is happening, it might be a BIOS issue that can simply be fixed in the next revision, or it can be an indicator of some problems on those frequencies. Regardless of the reasons, we confirmed our suspicions that there is something odd happening there and we strongly advise you to avoid the 1338MHz to 1454MHz range when overclocking, and keep it below 1920MHz.

*Chozart* · 05-23-07

Good to know... given my newest board

MADMAX22 · 05-23-07

interesting

JoBlo69 · 05-23-07

ha! thats why my chip is stable at 3.5 and 3.7 but is far from it at 3.6... good to know!!!

cognoscenti · 05-23-07

Quote:

Originally Posted by Chozart

Good to know... given my newest board

Nice choice of board!

This graph highlights the joy of having unlocked multis.

**Burn** · 05-23-07

Wrong link, I edited it for the right one.

And here is a graph of relative performance. Note the difference between actual and what they expected, in this graph:

Modki · 05-23-07

Why does performance go down as clockspeed goes up. Am I not reading these right

{core2duo}werd · 05-23-07

yeah i don't get what all this means.

Modki · 05-23-07

I see the dips that are the straps but overall it looks like performance goes down the higher up your Bus Speed goes?

*Chozart* · 05-23-07

note that it is relative performance.

Burns graph illustrates the 'expected' straps. Each time relative performance dips, there is a strap. The other graph, 'real' straps, has odd behavior between 1333 and 1456MHz.

It's like with RAM... see the straps as timings.

When you overclock RAM, there comes a point that you have to loosen timings... at that point, relative performance dips and unless you clock it a bit past that point, absolute performance will also be less for a while.

The motherboard does something similar when you overclock. At an FSB of 1284, it looses some timing somewhere.. called a 'strap'

In terms of absolute performance, this means that at 1283MHz you have better performance than at 1285MHz (the strap limits performance more than the clock speed makes up for it). However, at something like, say, 1315, clockspeed caught up with the hit of the strap. (Relative performance drops from 6.08 to 5.95, if I read the graph accurately enough, and thus at that point you need an FSB of 6.08/5.95 * 1284 to make up for the strap).

This is my understanding of all this

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680i SLI FSB Straps

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