Explanation of Turbo in i7

[zlojack]

I would like to get a clear explanation of the Turbo mode function in relatively simple terms.

My understanding is as follows:

i7 920 Turbo on + load on 4 cores = 21 Multi
i7 920 Turbo on + single-threaded load = 22 Multi (but this would drop to 21 if there is any load on the other cores)

Originally Speed Step needed to be enabled in order to implement Turbo but manufacturers have coded the bios in such a way as to circumvent this requirement and allow us to use Turbo for a permanent 21 multi and 22 in single-threaded apps.

Am I right on this?

[faster3200]

I think the 22 multi might depend on the mobo, but on the DFI you have to disable 3 out of the 4 cores to get the 22 multi, not just have a load on one. Also, the Turbo mode seems pretty fickle as when I have a normal load (gaming or something like that) I get the 21x multi, however when I put 100% load for stress testing it likes to drop in and out of turbo mode.

[rge]

According to intels turbo white paper, (I posted it in realtemp thread couple months ago...just to lazy to find it) you always have to disable all cores but one to get 22x multi on i920, so basically you can forget the 22x multi.

The 21 turbo multi depends on bios implentation.

Gigabyte bioses from F4beta on, all TDP, current, temp, and voltage limits for turbo are completely disabled, so really no turbo mode per se, more like turbo enabled = 21 multi. Using Gigabyte bios F3 (on Extreme) TDP, etc limits are enabled and turbo drops out at high load.
Testing bios F3 GB Extreme, using everest to monitor TDP (watts) and current the turbo will disengage near 120 watts or near the 130 watt TDP limit of the cpu. Testing bios F4 and F5 betas, running coredamage at 1.66 vcore at 4600mhz, everest reads over 200 watts at full load, and turbo is still engaged.

Currently, Gigabyte, I believe is the only bios that basically turns off TDP limits, and does not matter whether you enable C1E/EIST or not.

Asus drops out of turbo at certain load at certain OC's, but word is bios writers are working on a "fix" to run board same way as gigabyte, ie to ignore TDP, etc limits.

I have no idea what other boards do, but based on faster3200 post, it seems DFI still has turbo limits enabled or has not circumvented them.

If you have EVGA, you can get most recent version everest, monitor watts under sensor, and run your board high enough to exceed 150 watts and watch cpuz or realtemp or both and watch and see if multi drops after passing certain specs.

[zlojack]

I'll have to test that, rge. Thanks for the replies, guys.

From what I've seen, my CPU doesn't drop below 21 multi even at full Linpack load. I believe the implementation for EVGA is similar to what Gigabyte did, which is to basically add +1 to the multi with Turbo enabled.

I will do some tests with three cores disabled and see what it gives me.

[faster3200]

According to intels turbo white paper, (I posted it in realtemp thread couple months ago...just to lazy to find it) you always have to disable all cores but one to get 22x multi on i920, so basically you can forget the 22x multi.

The 21 turbo multi depends on bios implentation.

Gigabyte bioses from F4beta on, all TDP, current, temp, and voltage limits for turbo are completely disabled, so really no turbo mode per se, more like turbo enabled = 21 multi. Using Gigabyte bios F3 (on Extreme) TDP, etc limits are enabled and turbo drops out at high load.
Testing bios F3 GB Extreme, using everest to monitor TDP (watts) and current the turbo will disengage near 120 watts or near the 130 watt TDP limit of the cpu. Testing bios F4 and F5 betas, running coredamage at 1.66 vcore at 4600mhz, everest reads over 200 watts at full load, and turbo is still engaged.

Currently, Gigabyte, I believe is the only bios that basically turns off TDP limits, and does not matter whether you enable C1E/EIST or not.

Asus drops out of turbo at certain load at certain OC's, but word is bios writers are working on a "fix" to run board same way as gigabyte, ie to ignore TDP, etc limits.

I have no idea what other boards do, but based on faster3200 post, it seems DFI still has turbo limits enabled or has not circumvented them.

If you have EVGA, you can get most recent version everest, monitor watts under sensor, and run your board high enough to exceed 150 watts and watch cpuz or realtemp or both and watch and see if multi drops after passing certain specs.

Very nice explanation. I might have to send this to some friends who are confused how turbo works.

[zlojack]

Alright, if anyone feels up for it, have a read here and tell me what they think: http://www.evga.com/forums/tm.asp?m=...ey=&#100446595

It starts around post #5 and goes on for a couple of pages.

[rge]

http://download.intel.com/design/pro...=tech_tb+paper
turbo paper from intel

To test a given motherboard and bios, use cpuz 1.49, realtemp 3.0, and everest 5.0 trial is fine. Load prime on all cores (normal) and watch the multi in realtemp and cpuz. If still reads 21 on i920 you are in turbo mode.

All GB owners have figured out bios F3 follows intel rules and properly uses turbo. Under a certain load, turbo is active (number of cores loaded is not relevant, just total TDP of the load, along with current, temps. So first 3 pics are with the F3 GB bios that follows intel rules.

Pic 1, bios F3, C1E/EIST disabled (not relevant on this mobo/bios), turbo on. prime blend load affinity set on 1 core only (threads 0,1) (do not use small ffts to test as too much power draw and will kick turbo out sooner). NOTE multi is 23, turbo is active, loadtester shows 2 threads/1 core loaded as it should.

Pic 2, bios F3, all same as above except affinity now set to threads 0-3, ie 2 of 4 cores are loaded. 2 cores loaded (4 threads) per loadtester. NOTE multi is 23, turbo is active.

Pic 3, bios F3, same as above except affinity now set to threads 0-5, ie 3 of 4 cores active. NOTE wattage kicks up too high at 23 multi, so multi is now at 22, ie turbo has disengaged.

Pic 4, different bios, all F4betas and later bioses TDP and all limits are completely disengaged. Turbo is permanent regardless of load, TDP, current, temps, ie turbo = 23 multi on i940 or 21 multi on i920. pic is of coredamage + linx at high vcore and well over 200watts, well in excess of TDP limit of 130w.

Quotes from intel white paper
"It is possible for BIOS to contain a set-up option to
enable or disable Intel® Turbo Boost technology
and it operates under operating system (OS)
control by engaging when the OS requests the
highest performance state (P0).

"For example, one
particular processor may allow up to two
frequency steps (266.66 MHz) when just one core
is active and one frequency step (133.33 MHz)
when two or more cores are active."
NOTE to get only one core active, you have to disable all but one in bios, hence 2 step up multi 22 i920, 24 on i940 is useless.

"Intel® Turbo Boost technology automatically
allows processor cores to run faster than the base
operating frequency if the processor is operating
below rated power, temperature, and current
specification limits. Intel® Turbo Boost technology
can be engaged with any number of cores or
logical processors enabled and active."

"When Intel® Turbo Boost technology is
requested by the OS, the processor will commonly
operate between the max Intel® Turbo Boost
technology frequency and the base operating
frequency.
All active cores in the processor will operate at
the same frequency. Even at frequencies above
the base operating frequency, all active cores will
run at the same frequency and voltage."

So if all cores are fully loaded and multi reads 21 (i920) or 23(i940), you have turbo on all cores per intel white paper ref. above. And if you use high vcore and OC and load coredamage/linx etc and run TDP (watts) and current (A) monitored in everest way above 130W and ~100A and temps high in RT and you still have turbo, it is likely your bios has disabled TDP, etc limits, like intel clearly states you can in their whitepaper

Say thanks to Unclewebb for all the neat programs for testing this stuff.

[zlojack]

Thanks rge. Very nice and clear explanation there!

[eva2000]

For DFI UT X58-T3EH8 from http://i4memory.com/102537-post3.html



TDC/TDP & TM Protection (Turbo mode effects): In CPU Feature section of bios the Set VR Current Limit Max and Thermal Management Control options control TDC/TDP and other temperature related throttling for Core i7 cpu.

• TDC = over current protection which default Vcore OCP max is 140A (for CPU PWM IC). At >70A, TDC is tripped, it will disable Turbo mode - thus you may see your cpu multiplier drop by 1x or 2x.
• TDP = thermal design power according to DFI is tripped at around >80W which will also disable Turbo mode
• Set VR Current Limit Max = Enable to disable both TDC and TDP protection functions thus allowing Turbo mode to run without any TDC/TDP protection.
• Thermal Management Control = Tripped when core temp is >90C, Turbo mode will disable. At >105C core temp, will force system shutdown.
• Only when 965 cpu is installed are 2 additional options for TDC/TDP displayed for TDC Enable: x TDC Limit: and TDP Enable: Disabled x TDP Limit: 0