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6111
November 8th, 2011 13:00
Dell 6320 & Turbo Boost Issues
Recently I have noticed some weird performance characteristics around my E6320 laptop and similar behavior with a Toshiba R835 both of which have the i5 line of mobile Sandy Bridge processors from Intel. What I observe is that 'Turbo Boost' seems to be broken in both of these cases. It seems that Toshiba has put in a workaround to disable it. See my cross post around that and instructions on how to test your own machine at http://forums.toshiba.com/t5/Port%C3%A9g%C3%A9-Laptops/R835-P84-Intel-Turbo-Boost-amp-Enhanced-Speedstep-Disabled/td-p/234242.
Here is what I see (Intel i5-2520m, 2.5Ghz, 3.2Ghz Turbo):
SpeedStep Turbo Boost Max Frequency Multiplier [Expected]
Yes Yes 1.8Ghz 18 32 (upto depending on temp, cores in use)
Yes No 1.6Ghz 16 25
No Yes 2.5Ghz 25 32
No No 2.5Ghz 25 25
When Turbo Boost is enabled, it seems that not only is it not functioning, but it actually pegs the CPU at a lower frequency. Why does this matter. Well in reality if you have a machine that operates this way, you basically are only getting about 50% of the performance you paid for. No need to have purchased the expensive upgrade.
The obvious 'fix' if you have an affected system is to turn Speedstep OFF until Dell or Intel fix the root cause issue.
Test your own machine out and maybe we can identify which combinations or revisions of processor and chipset are affected.
P1000
4 Posts
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November 8th, 2011 15:00
P1000
4 Posts
0
November 8th, 2011 15:00
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P1000
4 Posts
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November 12th, 2011 14:00
I contacted the folks at Intel and they confirmed that they weren't aware of any issues with the actual hardware or chipset itself. I found a tool called ThrottleStop that allows you to modify the MSR (Model Specific Registers) after at runtime. You can manually change the clock multiplier to operate the maximum (Turbo). After doing this the processor runs just as expected and engages the Turbo boost up to the processor rating. Clearly this is either a bug with the BIOS or an intentional design 'feature' that was implemented by Dell to improve battery life or because of thermal dissipation issues. If it is a design feature then Dell needs to mark it as permanently throttled to 1.8Ghz and then market it that way. The design tradeoff issues is really around heat dissipation. That is something that still that can be worked around as both the platform and the hardware allow the CPU to be automatically throttled when the junction temperature of the CPU exceeds either the hardware limit or the platform design limit. After paying a premium for a business level machine with a higher performance processor, this is a somewhat ridiculous situation.