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Thread: what is "safe" Vcc?




  1. #1
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    Default what is "safe" Vcc?

    Hello All.

    After I've successfully overclocked my system to 9.5x400@2.00D and 9.5x422@2.00D; and then "squeezed" all settings to absolute stable minimums; I decided to go for 9.5x444@2.00D over this past weekend.

    I think that I'm closing in on pretty good stability, with a 7.5Hr. duration p95 blended test yesterday, before one (of two) core failed.

    The only issue, that I see is that the Vcc required for 9.5x444 seems to be (at least) 1.3875v. The Intel spec for my chip states 1.350v as the max. In CPU-ID, at boot-up the max. voltage reads:1.36v, but then under p95 load, this value drops (or is it droops?) to ~1.31v-1.33v.

    So, am I still operating within Intel Spec? Or have I exceeded it? I'm wondering if I determine that I need an xtra click or two in Vcc to get this config completely stable if I can go ahead and do it without concern for damaging my system? I've extinguished all other possible fixes, and have tried many combinations of likely settings for: Vtt, Pll, MCH, MCH Ref, DRAMv. The 9.5x444 config definitely likes: Vtt=1.28v, PLL=1.57v, MCH=1.24v, MCH Ref=0.74v (when Vtt=1.20v). My last ditch effort to get stable without raising Vcc is running now, into the 7hr.mark last I checked, with PLL=1.50v. If that one fails, the only other option I see is to raise Vcc a click, and try that? Or maybe invoke Load Line Calibration with Vcc set 1.33-1.35?

    (Note: I have no plans to run things at this config 24/7, and will likely use my 9.5x422@2.00D config for that.)

    Max. core temps (RealTemp, uncalibrated) read 64c under p95 load., which is still within reason, correct?

    I was pretty surprised that going from 9.5x422 to 9.5x444 required such a large jump in Vcc. I'm running FSB422@Vcc=1.3125v (stable 24+hrs. in p95 blended)

    Also, with this BIOS, is there a way to set it up so you are prompted at start-up to select a pre-set BIOS config to run? Ideally, I like to present 4 choices: "Standard" (9.5x333), "Fast" (9.5x400), "Turbo" (9.5x422), "Extreme" (9.5x444)
    Last edited by corlay; 07-13-2009 at 11:50 PM.
    case: Gigabyte 'Triton 180'
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    cpu: Intel 'e8500' (E0)
    cooling: Xigmatek 'HDT-S1283'
    memory: OCZ 'Reaper' 4x2gb (OCZ2RPR10664GK)
    storage: Western Digital 'Black' (500gb)
    video: EVGA 'GeForce' GTX-260
    display: Samsung 'SyncMaster' 2333sw

  2. #2
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    Default Re: what is "safe" Vcc?

    Your processor, as with all 45nm dual cores and quads is rated up to 1.3625V, not 1.35V, as detailed here: Intel® Core?2 Duo Desktop Processor E8500 - SLB9K .

    PLL up to 1.65 is acceptable. Worth trying but 99% sure it will make little difference.

    I can't say if your temps are ok because as you said, they're uncalibrated readings, which are about as good as a chocolate fire guard. Unless your core sensors are stuck at idle, calibrating them is essential. If you look in my sig, mine are both stuck. One reads 34c and the other 39c even when underclocked to 1.6GHz at ~1V. My load temps appear to be good, but who knows what they really are?

    Use as much Vcore as you feel comfortable with. I must say though, if you need over 1.3625V for 3.8GHz on an E0 E8500, either you still need to tweak your settings or you got unlucky in a big way with the amount of OC headroom on that particular piece of silicon.
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  3. #3
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    Default Re: what is "safe" Vcc?

    Quote Originally Posted by Psycho101 View Post
    Use as much Vcore as you feel comfortable with. I must say though, if you need over 1.3625V for 3.8GHz on an E0 E8500, either you still need to tweak your settings or you got unlucky in a big way with the amount of OC headroom on that particular piece of silicon.
    Psycho,

    Thanks for the reply.

    Yes, if I do get stable, and plan to run this 9.5x444 config for any amount of time, I'll surely go through the steps of calibrating RealTemp.

    I think you mis-understood my OP?
    I'm needing 3.875v for 4.21GHz (9.5x444),
    not 3.8GHz.

    Thanks for clarifying the max. rated voltage.
    Not sure why I thought it was 1.350v?

    But, can you answer one of my original questions:
    Does the BIOS setting matter to the chip, or shall I only be concerned about the CPU-ID reading of actual voltages supplied, with regard to exceeding the rated Intel maximum?

    Thanks...
    case: Gigabyte 'Triton 180'
    power: Corsair 'HX-620'
    motherboard: Gigabyte 'GA-EP45-UD3P' (rev.1.1, F9)
    cpu: Intel 'e8500' (E0)
    cooling: Xigmatek 'HDT-S1283'
    memory: OCZ 'Reaper' 4x2gb (OCZ2RPR10664GK)
    storage: Western Digital 'Black' (500gb)
    video: EVGA 'GeForce' GTX-260
    display: Samsung 'SyncMaster' 2333sw

  4. #4
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    Default Re: what is "safe" Vcc?

    Also, with this BIOS, is there a way to set it up so you are prompted at start-up to select a pre-set BIOS config to run? Ideally, I like to present 4 choices: "Standard" (9.5x333), "Fast" (9.5x400), "Turbo" (9.5x422), "Extreme" (9.5x444)
    You can create up to 8 different saved bios settings. See this post for profile information. I would avoid trying to use the EasyTune6 "boost" options.

    For more help and memory tweaking help, post your current bios settings using this generic bios template:
    Code:
    Motherboard: Model:  Rev#:  Bios Version:
    Cpu: Model
    Ram: Brand, Model/Part#, Link to your ram's specs
    Power Supply Unit: Brand, Model#, Wattage
    
    Default settings for new setups that are not overclocked.
    
    note: replace all ?? with the value displayed in your bios.
    ----> Replace "Auto" with manually set values.
    
    MB Intelligent Tweaker(M.I.T.)
    Robust Graphics Booster -------------- : [Auto] <--- FAST is OK
    CPU Clock Ratio ---------------------- : [##]
    Fine CPU Clock Ratio ----------------- : [0.0] < ignore if not available
    CPU Frequency ---------------------: ####
    
    Clock Chip Control
    Standard Clock Control
    CPU Host Clock Control --------------- : [Enabled]
    CPU Host Frequency (Mhz) --------------: [Mhz]
    PCI Express Frequency (Mhz) ---------- : [Auto] <--- Set to 100, never leave this on Auto
    
    C.I.A.2 ------------------------------ : [Disabled]
    
    Advanced Clock Control ------- [Press Enter]
    CPU Clock Drive ---------------------- : <<< 800
    PCI Express Clock Drive -------------- : <<< 900
    CPU Clock Skew (ps) ------------------ : <<<
    MCH Clock Skew (ps) ------------------ : <<<
    
    DRAM Performance Control
    Performance Enhance ------------------- : [Turbo] <--- set to DISABLED when overclocking
    Extreme Memory Profile --- (X.M.P.) --- : [Disabled] <--- Leave this Disabled
    (G)MCH Frequency Latch ---------------- : [Auto]
    System Memory Multiplier -------------- : [Auto]
    Memory Frequency (Mhz) ---------------- : [Auto]
    DRAM Timing Selectable ---------------- : [Auto] <-- set to MANUAL for overclocking
    
    Standard Timing Control
    CAS Latency Time -------- ?? ---------- : [Auto]
    tRCD  ------------------- ?? ---------- : [Auto]
    tRP --------------------- ?? ---------- : [Auto]
    tRAS  ------------------- ?? ---------- : [Auto]
    
    Advanced Timing Control
    tRRD  ------------------- ?? ---------- : [Auto]
    tWTR  ------------------- ?? ---------- : [Auto]
    tWR --------------------- ?? ---------- : [Auto]
    tRFC  ------------------- ?? ---------- : [Auto]
    tRTP  ------------------- ?? ---------- : [Auto]
    Command Rate (CMD) -------------------- : [Auto] <--- Auto or 0 is OK
    
    Driving Strength Profiles
    Driving Strength --------- : Press Enter <--- press ENTER to modify memory sub-timings when overclocking
    
    Channel A
    Static tRead Value --------------------- : [Auto]
    tRD Phase0 Adjustment ------------------ : [Auto] <-- leave this and below set to AUTO
    tRD Phase1 Adjustment ------------------ : [Auto]
    tRD Phase2 Adjustment ------------------ : [Auto]
    tRD Phase3 Adjustment ------------------ : [Auto]
    Trd2rd(Different Rank) ----------------- : [Auto]
    Twr2wr(Different Rank) ----------------- : [Auto]
    Twr2rd(Different Rank) ----------------- : [Auto]
    Trd2wr(Same/Diff Rank) ----------------- : [Auto]
    Dimm1 Clock Skew Control --------------- : [Auto]  ps
    Dimm2 Clock Skew Control --------------- : [Auto]  ps
    
    Channel B
    Static tRead Value --------------------- : [Auto]
    tRD Phase0 Adjustment ------------------ : [Auto] <-- leave this and below set to AUTO
    tRD Phase1 Adjustment ------------------ : [Auto]
    tRD Phase2 Adjustment ------------------ : [Auto]
    tRD Phase3 Adjustment ------------------ : [Auto]
    Trd2rd(Different Rank) ----------------- : [Auto]
    Twr2wr(Different Rank) ----------------- : [Auto]
    Twr2rd(Different Rank) ----------------- : [Auto]
    Trd2wr(Same/Diff Rank) ----------------- : [Auto]
    Dimm1 Clock Skew Control --------------- : [Auto]  ps
    Dimm2 Clock Skew Control --------------- : [Auto]  ps
    
    Motherboard Voltage Control
    CPU
    Voltage Types------------ Normal -------- Current -----
    Load-Line Calibration ----------------- : [Disabled]
    CPU Vcore --------------- 1.?????  ---- : [Auto] <--- set to the 1.????? value
    
    CPU Termination --------- 1.200V* ----- : [Auto] <--- set to the value to the left (Auto over-volts this too much when overclocking) Auto is OK if not overclocking
    CPU PLL ----------------- 1.500V* ----- : [Auto] <--- set to the value to the left (Auto over-volts this too much when overclocking) Auto is OK if not overclocking
    
    CPU Reference ----------- 0.755V* ----- : [Auto] <--- Auto Will set this correctly
    CPU Reference2 ---------- 0.800V* ----- : [Auto] <--- Auto Will set this correctly
    
    MCH/ICH
    MCH Core ---------------- 1.100V ------- : [Auto] <--- set to 1.20 for 2x2GB ram (1.24 - 1.26, or 1.05 might be needed)
    MCH Reference ----------- 0.800V ------- : [Auto]
    MCH/DRAM Ref ------------ 0.900V  ------ : [Auto]
    ICH I/O ----------------- 1.500V ------- : [Auto] <--- set to the value to the left
    ICH Core ---------------- 1.100V ------- : [Auto] <--- set to the value to the left
    DRAM
    DRAM Voltage ------------ 1.800V ------- : [Auto] <--- set to the max rated ram voltage (for most memory)
    DRAM Termination -------- 0.900V ------- : [Auto]
    Channel A Reference ----- 0.900V ------- : [Auto]
    Channel B Reference ----- 0.900V ------- : [Auto]
    
    Advanced Settings
    Limit CPUID Max. to 3 ------------------ : [Disabled]
    No-Execute Memory Protect -------------- : [Enabled]
    CPU Enhanced Halt (C1E) ---------------- : [Disabled]
    C2/C2E State Support ------------------- : [Disabled]
    x C4/C4E State Support ----------------- : [Disabled]
    CPU Thermal Monitor 2 (TM2) ------------ : [Enabled]
    CPU EIST Function  --------------------- : [Disabled]
    Virtualization Technology -------------- : [Disabled] <--- Enabled if you use Vmware/Virtual PC
    
    Integrated Peripherals
    Legacy USB Storage Detect  ------------- : [Enabled] <--- set to Disabled when overclocking (this must be enabled to flash or boot from a USB drive)
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  5. #5
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    Default Re: what is "safe" Vcc?

    I see. 4.21GHz with 1.38V isn't to bad.

    The only way to tell actual voltages would be to use a DMM at the measuring points on the board. PC Health, CPU-Z and OCCT will all tell you different things, and none of them are 100% accurate when we're talking in such small fractions of voltage.

    IMO, without using a DMM, you can only ever be 100% sure you're not giving an ounce more than 1.3625V unless you set 1.3625V in the BIOS with LLC off. Intel have no way to verify the exact voltage you've given to the CPU. They will certainly be able to identify damage caused by a significant over volt, but only if they test all returns in detail. A small discrepancy won't do any harm.

    The only reason I'm running 1.425V (1.45625 in BIOS) is because I can afford to replace the CPU if it goes pop. However after a couple of months use, so far so good.

    Edit** There's no way to choose configs from a selectable menu. You'll have to enter the BIOS each time and load a saved profile, then save and exit.
    Coolermaster CM 690 II advance Case
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  6. #6
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    Default Re: what is "safe" Vcc?

    Quote Originally Posted by profJim View Post
    You can create up to 8 different saved bios settings.
    Jim, thanks.

    I do realize that I can save different configs in the BIOS interface, and have done so.

    But my question is:
    Can you configure your boot sequence to halt and force the User to *select* on of these saved BIOS configs, before continuing on to Windows?

    PS I didn't post my current settings in this thread, because my question(s) were general in nature and are not reliant upon what my BIOS settings are at the moment.
    case: Gigabyte 'Triton 180'
    power: Corsair 'HX-620'
    motherboard: Gigabyte 'GA-EP45-UD3P' (rev.1.1, F9)
    cpu: Intel 'e8500' (E0)
    cooling: Xigmatek 'HDT-S1283'
    memory: OCZ 'Reaper' 4x2gb (OCZ2RPR10664GK)
    storage: Western Digital 'Black' (500gb)
    video: EVGA 'GeForce' GTX-260
    display: Samsung 'SyncMaster' 2333sw

  7. #7
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    Default Re: what is "safe" Vcc?

    Quote Originally Posted by Psycho101 View Post
    IMO, without using a DMM, you can only ever be 100% sure you're not giving an ounce more than 1.3625V unless you set 1.3625V in the BIOS with LLC off.
    Do you think it's a viable alternative to set Vcc about where CPU-ID reports the voltage levels under load, and enable Load Line Calibration? Or am I better off leaving LLC off, and over-volting Vcc in excess of 1.3625v?

    I've read that LLC might result in voltage spikes that greatly exceed the Vcc setting in the BIOS and that scares me a bit....At least with LCC off you know what the max. voltage delivered will be.
    case: Gigabyte 'Triton 180'
    power: Corsair 'HX-620'
    motherboard: Gigabyte 'GA-EP45-UD3P' (rev.1.1, F9)
    cpu: Intel 'e8500' (E0)
    cooling: Xigmatek 'HDT-S1283'
    memory: OCZ 'Reaper' 4x2gb (OCZ2RPR10664GK)
    storage: Western Digital 'Black' (500gb)
    video: EVGA 'GeForce' GTX-260
    display: Samsung 'SyncMaster' 2333sw

  8. #8
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    Default Re: what is "safe" Vcc?

    LLC definately does cause voltages to go out of the range you set. This means that at 1.3625V and LLC on you can be 90% sure that at some point(s) your CPU is getting more than 1.3625V.

    Don't count out LLC though. I'd test with it enabled at 1.35V or there abouts. Now that you definately need more than 1.3625V with it off, it's worth a try.
    Coolermaster CM 690 II advance Case
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    2 x 2GB Mushkin Ridgeback (996902), @ 7-10-8-27, 2010-DDR, 1.66v
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    3 x 140 MM Coolermaster LED fans (one front intake, one top extraction, one side intake)
    Dell Ultra Sharp 2209WAf E-IPS @ 1680x1050

  9. #9

    Default Re: what is "safe" Vcc?

    If you want to keep the Vcc within the functional operation limits Intel specifies, this means limiting the BIOS setting to 1.3625V with LLC disabled. This is the only guaranteed way to maintain the CPU Vcc transients (voltages spikes during load state changes) within the specification.
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  10. #10
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    Default Re: what is "safe" Vcc?

    Quote Originally Posted by Psycho101 View Post
    Don't count out LLC though. I'd test with it enabled at 1.35V or there abouts.
    When I returned home yesterday, my latest attempt made it 10 hrs. in p95:
    Vcc=1.3875
    Vtt=1.28
    PLL=1.50
    MCH=1.24

    I then tried LLC=Enabled and Vcc=1.350v and that resulted in a p95 Windows error (not a BSOD, and not a regular error in p95, but a Windows message that p95 had to be halted...) which usually means that I'm getting close. These types of errors seem to exist when voltages are sufficient enough to prevent a BSOD, but not sufficient enough for p95 to stress the system fully.

    So,
    I upped Vcc to 1.35625v and got 6hrs. out of it over-night.

    This am, I upped Vcc once more to 1.3625v. We'll see if that does it when I return home tonight.
    If this last attempt doesn't pass p95, I may revert back to LLC=Disabled, and set my Vcc one-up,
    from my best attempt with LLC off (10hrs.in p95) which would be ~1.39-ish
    Last edited by corlay; 07-14-2009 at 09:43 PM.
    case: Gigabyte 'Triton 180'
    power: Corsair 'HX-620'
    motherboard: Gigabyte 'GA-EP45-UD3P' (rev.1.1, F9)
    cpu: Intel 'e8500' (E0)
    cooling: Xigmatek 'HDT-S1283'
    memory: OCZ 'Reaper' 4x2gb (OCZ2RPR10664GK)
    storage: Western Digital 'Black' (500gb)
    video: EVGA 'GeForce' GTX-260
    display: Samsung 'SyncMaster' 2333sw

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