How to lock i7-920 multiplier at 21x on Intel Smackover DX58SO

[aph]

After waiting a month to get my account validated, I wanted to post something useful I just figured out today. To lock the multiplier at 21x on the Intel DX58SO motherboard all you have to change in the BIOS is this option:

CPU VR Current Limit Override: change to [Enable]



Strangely, this is not in ANY of the reviews. I figured it out after fitzing with HWMonitor and reading the 60 page long thread here about the modded unofficial P6TDeluxe V1 BIOS.

The description for Intel Turbo Boost Technology is: "Enable to allow system to dynamically change processor speed and voltage based on load and power limits." Power doesn't refer to voltage, it refers to current.

The Asus mod causes the mobo to think the CPU is taking less current than it is, preventing the throttling from taking place. This does the same thing, only it's built right in to the official BIOS. The CPU VR Current Limit Override option removes that block.

This gives me all locked 21.0x on i7 Turbo V8 regardless of LinX/Prime95 load. With this option and the fact that I can get this board to 218 BCLK, I think it definitely qualifies as an enthusiast board.

And because you don't have to fuss with the C states or EIST to get 21x this way, you can still get the 22x multi in single-threaded/moderate load cases. To my knowledge the Intel board is the only one that can get the 22x max with a 21x min.

[dengyong]

Do three cores have to be disabled to get the 22x multi ?

[aph]

That's one way to do it, but it does switch to 22x with all cores enabled at load if only one is being used. Check out the SuperPI graphs at X-bit:



Other boards can't get to 22x because they have to have C state disabled to get to 21x.

[jcool]

Actually the DFI with 0619 Bios jumps to 22x with one thread loaded. Drove me NUTS until I found out, I was running 191x21 and primestable, but the Deep Freeze test in 3D06 always, well froze
Because it jumped to 4,2...

[aph]

I had a bit of the same issues. P95 would BSOD out of nowhere after 30 mins. I was never looked close enough to catch the multi at 22x in i7 Turbo V8 but disabling "C state" capped it at 21x and resolved the crashes. Here are the settings for the various multipliers.

22x requires:
- "Enhanced Intel SpeedStep Technology"
- "Intel Turbo Boost Technology"
- "CPU VR Current Limit Override"
- "C state"
21x requires:
- Same as above but with "C state" disabled

I don't see C1E having any kind of effect on the multis or the power drain, at least with "C state" disabled.

[unclewebb]

On a Core i7 920, it is possible to get a +2 turbo boost if only 1 core is enabled in the bios or if all 4 cores are enabled in the bios but only 1 core is active.

Intel defines a core as being active if it is in either the C0 or C1 state. To get a 22X multiplier, the other 3 cores need to be inactive in either the C3 or C6 sleep state.

When running a single threaded benchmark with 4 cores enabled in the bios, the CPU will typically cycle hundreds of times a second between 21 and 22. As soon as some background task needs to be processed, a second core wakes up and becomes active which throttles the multiplier back to 21. When that task is finished, that core goes back to sleep so only one core is active again and the multiplier is allowed to go back up to 22.

I think all X58 motherboards support this basic feature. The difference is that the Intel board is one of the few boards that supports this feature even when overclocking the BCLK. Most boards (Gigabyte, Asus) limit the maximum turbo boost to only +1 (21) as soon as you start overclocking.

to Intel for doing this right.

I was helping a user today and he found that his new MSI P55 board is able to use the full +4 bins of turbo boost on his i5 750 when he is overclocking so hopefully the motherboard guys are finally following the Intel spec.

aph: I read the X-Bit article but the problem I have with their nice graphs is that I don't think the software they were using is accurate enough to correctly report the multiplier when running a single threaded task.

The multiplier can be changing hundreds of times a second so the software they were using that only samples the multi once per second is inadequate.

When running a single thread of SuperPI, what does i7 Turbo show? Typically the thread that has the biggest load on it will have an average multiplier of about 21.750. This will constantly vary depending on how much background activity is going on. This is a sign that this thread has been able to use the 22 multi about 75% of the time and has had to drop down to 21 due to background activity processing the other 25% of the time.

Can you post a screen shot of SuperPI mod and i7 Turbo about half way through a 1M run so I can see how the threads are reporting on your board when overclocking. Maybe I'll send your screen shot to the Asus rep to show him how a motherboard is supposed to handle Intel Turbo Boost.

Here's the latest version of i7 Turbo. Mostly minor tweaks lately for better compatibility with the new Core i7/i5 and the Core 2 mobile processors that support Intel Dynamic Acceleration (IDA) which also gives the multi a +1 boost when running a single threaded app.

http://www.fileden.com/files/2008/3/3/1794507/Turbo.zip