Overclock.net › Forums › Intel › Intel CPUs › What does vccsa and vccio actually do?
New Posts  All Forums:Forum Nav:

What does vccsa and vccio actually do?

post #1 of 17
Thread Starter 
I know this question has been ask many time before. but it seems there're different answers to this same old question.
popular opinion is that VCCSA is System Agent Voltage, and it stabilizes or helps overclock BLCK, while VCCIO (commomly known as VTT/QpI) is IMC Voltage and helps stabilize when overclocking RAM .
Quote:
VCCIO: more commonly known at QPI/VTT voltage, this is the VTT voltage. Formally known as Processor Power for I/O it is the voltage for the integrated memory controller as well as the PCI-E controller.
But an article from hardwaresecrets has exactly the opposite opinion, it says
Quote:
VTT: This is the rail that feeds the integrated memory controller (on CPUs that have this component), the QPI bus (on CPUs that have this component), the FSB termination (on CPUs that are based on this architecture), the L3 memory cache (on CPUs that have this feature), the thermal control bus (PECI, Platform Environmental Control Interface, on CPUs that have this feature, except from second-generation Core i processors on, where this bus is fed by the VCCIO voltage) and other circuits, depending on the CPU. It is important to understand that on AMD CPUs, “VTT” is the name of a different voltage; the VTT on Intel CPUs is the equivalent of the VDDNB from AMD CPUs. This voltage can be changed through options such as “CPU VTT,” “CPU FSB,” “IMC Voltage,” and “QPI/VTT Voltage.”
•VCCSA: Starting with the second-generation Core i processors (“Sandy Bridge”), the VTT voltage was renamed to VCCSA, and is called “system agent.” It feeds the integrated PCI Express controller, memory controller, and display engine (i.e., the “2D” part of the graphics engine).
•VCCIO: Available starting with the second-generation Core i CPUs (“Sandy Bridge”), this voltage is used for feeding all input/output (I/O) pins of the CPU, except memory-related pins. On CPUs that have this voltage, it is also used to feed the thermal control bus (PECI, Platform Environmental Control Interface).
From the article we can see, VTT was renamed to VCCSA not VCCIO ,and it feeds voltage to the IMC, while VCCIO is voltage for (I/O) pins of the CPU, except memory-related pins, in their opinion it seems VCCIO has nothing to do with IMC.
so which one really powers IMC, VCCSA or VCCIO? My sense is that since VCCSA is system agent voltage and IMC is part of system agent, it's logical to say VCCSA powers IMC, then what does VCCIO do? now VCCIO is split into VCCIO-A and VCCIO-D, what's difference between them then, how do they function differently?
thanks.

links:
http://www.tomshardware.com/forum/266192-29-vccio-vccsa
http://www.hardwaresecrets.com/article/Understanding-All-Voltage-Configurations-from-the-Motherboard/995/4
post #2 of 17
More info
http://forums.anandtech.com/showthread.php?t=2312032
My System
(15 items)
 
  
CPUMotherboardGraphicsRAM
FX6300 Black M5A99X EVO R2.0 Nvidia GTS450 Team Vulcan PC3 12800 
Hard DriveOptical DriveCoolingOS
Samsung 840 PRO Asus DRW-1608P (x2) Custom Water Cooling Win7 (Ult), Win 8.1 & Win Server 2012 R2 
MonitorKeyboardPowerCase
2 X Samsung 915N Ducky Shine III, Blue Cherry/Blue LEDs PCP&C 1kw Lian Li PC-71 (W/Window) 
MouseAudio
Logiteck G400s none 
  hide details  
Reply
My System
(15 items)
 
  
CPUMotherboardGraphicsRAM
FX6300 Black M5A99X EVO R2.0 Nvidia GTS450 Team Vulcan PC3 12800 
Hard DriveOptical DriveCoolingOS
Samsung 840 PRO Asus DRW-1608P (x2) Custom Water Cooling Win7 (Ult), Win 8.1 & Win Server 2012 R2 
MonitorKeyboardPowerCase
2 X Samsung 915N Ducky Shine III, Blue Cherry/Blue LEDs PCP&C 1kw Lian Li PC-71 (W/Window) 
MouseAudio
Logiteck G400s none 
  hide details  
Reply
post #3 of 17
Quote:
Originally Posted by masterding View Post

I know this question has been ask many time before. but it seems there're different answers to this same old question.
popular opinion is that VCCSA is System Agent Voltage, and it stabilizes or helps overclock BLCK, while VCCIO (commomly known as VTT/QpI) is IMC Voltage and helps stabilize when overclocking RAM .
But an article from hardwaresecrets has exactly the opposite opinion, it says
From the article we can see, VTT was renamed to VCCSA not VCCIO ,and it feeds voltage to the IMC, while VCCIO is voltage for (I/O) pins of the CPU, except memory-related pins, in their opinion it seems VCCIO has nothing to do with IMC.
so which one really powers IMC, VCCSA or VCCIO? My sense is that since VCCSA is system agent voltage and IMC is part of system agent, it's logical to say VCCSA powers IMC, then what does VCCIO do? now VCCIO is split into VCCIO-A and VCCIO-D, what's difference between them then, how do they function differently?
thanks.

links:
http://www.tomshardware.com/forum/266192-29-vccio-vccsa
http://www.hardwaresecrets.com/article/Understanding-All-Voltage-Configurations-from-the-Motherboard/995/4

You did not list what part you were asking about. VccSA is a pre-haswell term that is still used. On 5960x, the "system agent" you see in bios is an offset for allowing memory overclocking, that's it.
post #4 of 17
Thread Starter 
Quote:
Originally Posted by billbartuska View Post

More info
http://forums.anandtech.com/showthread.php?t=2312032
It pretty much supports the first opinion. no doubt vccsa is system agent voltage ,we can come to the conclusion from the name, SA I assume is the acronym for system agent , but since IMC is part of system agent, how come VCCSA doesn't powers IMC?
post #5 of 17
Thread Starter 
Yes,VCCSA and VCCIO are pre-haswell terms , now VCCIO is split into VCCIO-A and VCCIO-D. but if we understand pre-haswell terms , I think it'll help understand haswell terms. So first
I want to know what does VCCSA and VCCIO do ,and then I want to know what does VCCIO,VCCIO-A ,VCCIO-D do.tongue.gif
post #6 of 17
Quote:
Originally Posted by masterding View Post

Yes,VCCSA and VCCIO are pre-haswell terms , now VCCIO is split into VCCIO-A and VCCIO-D. but if we understand pre-haswell terms , I think it'll help understand haswell terms. So first
I want to know what does VCCSA and VCCIO do ,and then I want to know what does VCCIO,VCCIO-A ,VCCIO-D do.tongue.gif

You will not find accurate data on Haswell for this. Sorry. The terms you have are wrong with haswell.
post #7 of 17
Test it.. best way to see what happens, let's use HWinfo terms as everyone uses this.

CPU Digital I/O voltage = VTT in HWinfo. CPU System Agent voltage = VCCSA in HWinfo. Though I can set it in BIOS, I don't see CPU Analog I/O voltage listed in any tool for my board.

For me, when I use the Auto values and running XMP they're set to: 1.112v VTT and 0.832v VCCSA. My OC is stable (not starting a fight on this) but it will fail Prime 28.5 Blend pretty much instantly.

If I change IO/D or IO/A nothing changes, Prime 28.5 remains as unstable (close to instant 124 BSOD). But if I raise System Agent by 0.15v (now it's 0.984v) then there's Prime stability that didn't exist.

Core x48 @ 1.345v / Cache x44 @ 1.24v / RAM @ 2200MHz. My conclusion, you want to play with SA.
Just a 'puter
(18 items)
 
  
CPUMotherboardGraphicsRAM
Intel Core i7 6700K ASUS Maximus VIII Hero iGPU thanks to Nvidia 970 3.5GB Corsair Vengeance LPX CMK8GX4M2B3200C16 
Hard DriveHard DriveCoolingCooling
Samsung 950 PRO 512GB Crucial M4 256GB RX360 V3 Koolance CPU-380I 
CoolingCoolingOSMonitor
Koolance RP-452X2 Reservoir Koolance PMP-450 12V Variable Speed Pump Windows 10 Pro x64 benq XL2411Z 
KeyboardPowerCaseMouse
logitech G510 Seasonic X-760 Corsair 800D Mionix Castor 
AudioAudio
Creative Sound Blaster X-Fi Titanium HD DT 990 Premium 250Ohm 
  hide details  
Reply
Just a 'puter
(18 items)
 
  
CPUMotherboardGraphicsRAM
Intel Core i7 6700K ASUS Maximus VIII Hero iGPU thanks to Nvidia 970 3.5GB Corsair Vengeance LPX CMK8GX4M2B3200C16 
Hard DriveHard DriveCoolingCooling
Samsung 950 PRO 512GB Crucial M4 256GB RX360 V3 Koolance CPU-380I 
CoolingCoolingOSMonitor
Koolance RP-452X2 Reservoir Koolance PMP-450 12V Variable Speed Pump Windows 10 Pro x64 benq XL2411Z 
KeyboardPowerCaseMouse
logitech G510 Seasonic X-760 Corsair 800D Mionix Castor 
AudioAudio
Creative Sound Blaster X-Fi Titanium HD DT 990 Premium 250Ohm 
  hide details  
Reply
post #8 of 17
Not sure about what they are exactly doing but the I/o D can actually harm memory overclocking if tuned to high. in the ROG Guides for Z87 Maximus they explain every single bios setting.

Also System Agent does directly affect the IMC for Haswell and 1.3 is a safe max and good to set to when overclocking the cpu so as to make sure that its not the IMC being weak causing instability.
Fresh Phenom 007
(12 items)
 
 
CPUMotherboardGraphicsRAM
4790k ASUS Maximus Impact 7 GTX 470 G.Skill Trident 2400 Cas 9 
Hard DriveHard DriveCoolingOS
Plextor M5 Western Digital 2.5" D5 Custom Loop Windows 8 
MonitorKeyboardPowerCase
50" HDTV Logitech K400R Silverstone SX-600-G Bitfenix Phenom M 
  hide details  
Reply
Fresh Phenom 007
(12 items)
 
 
CPUMotherboardGraphicsRAM
4790k ASUS Maximus Impact 7 GTX 470 G.Skill Trident 2400 Cas 9 
Hard DriveHard DriveCoolingOS
Plextor M5 Western Digital 2.5" D5 Custom Loop Windows 8 
MonitorKeyboardPowerCase
50" HDTV Logitech K400R Silverstone SX-600-G Bitfenix Phenom M 
  hide details  
Reply
post #9 of 17
Thread Starter 
Quote:
Originally Posted by error-id10t View Post

Test it.. best way to see what happens, let's use HWinfo terms as everyone uses this.

CPU Digital I/O voltage = VTT in HWinfo. CPU System Agent voltage = VCCSA in HWinfo. Though I can set it in BIOS, I don't see CPU Analog I/O voltage listed in any tool for my board.

For me, when I use the Auto values and running XMP they're set to: 1.112v VTT and 0.832v VCCSA. My OC is stable (not starting a fight on this) but it will fail Prime 28.5 Blend pretty much instantly.

If I change IO/D or IO/A nothing changes, Prime 28.5 remains as unstable (close to instant 124 BSOD). But if I raise System Agent by 0.15v (now it's 0.984v) then there's Prime stability that didn't exist.

Core x48 @ 1.345v / Cache x44 @ 1.24v / RAM @ 2200MHz. My conclusion, you want to play with SA.

According to Raja's "Maximus VI Series UEFI Guide for Overclocking ",
Quote:
VCCSA: System agent voltage. Helps with DRAM overclocking. 1.15~1.30 is more than enough for maximizing DRAM clocks. You can use 1.30v when pushing high DRAM frequencies to take the IMC out of the equation.


IO A: IO analog voltage. May help with DRAM overclocking. 1.15~1.30 is more than enough for maximizing DRAM Clocks most times.


IO D voltage: IO digital voltage. Critical rail for DRAM overclocking. 1.15~1.30 is more than enough for maximizing DRAM frequency. IO D can be sensitive on some processors when cold and too high may worsen cold bug behaviour. The right level of I/O A and I/O D will help maximize memory OC, too much or too little can cause code ‘55’ on the Hex display during POST or induce instability.


Find the right combination of SA/IOA/IOD for your setup and frequency – it will help push DRAM further. It may not be this same combination of voltages throughout all frequencies, it may be different at different frequencies, even on the same setup.
His conclusions is they all help with DRAM overclocking, but IOD is most critical one, though he didn't explain why, and didn't point out which one really powers IMC.
post #10 of 17
But does that mean anything to you? I know it means nothing to me and I'm sure like you many have read that before.

Play around and let us know what you see. I already mentioned what I see, IO/D and IO/A does nothing for me and how can I even make this work when I cannot even see what IO/A is set to, where-as SA helps. Same with Switching frequencies, if I change this from Auto to 500 (max for me) I start BSOD again.

update.

Been playing around raising Cache until it all went belly up again, tried raising SA from 0.15v up to 0.30v with no difference so then I moved to IO/D. Raised this to 0.15v and found some stability, 0.20v increased it again. But changing IO/A kills stability straight away. So for now (for my chip):

SA = +0.15v (0.984v)
IO/D = +0.20v (1.216v)
Edited by error-id10t - 10/18/14 at 7:06pm
Just a 'puter
(18 items)
 
  
CPUMotherboardGraphicsRAM
Intel Core i7 6700K ASUS Maximus VIII Hero iGPU thanks to Nvidia 970 3.5GB Corsair Vengeance LPX CMK8GX4M2B3200C16 
Hard DriveHard DriveCoolingCooling
Samsung 950 PRO 512GB Crucial M4 256GB RX360 V3 Koolance CPU-380I 
CoolingCoolingOSMonitor
Koolance RP-452X2 Reservoir Koolance PMP-450 12V Variable Speed Pump Windows 10 Pro x64 benq XL2411Z 
KeyboardPowerCaseMouse
logitech G510 Seasonic X-760 Corsair 800D Mionix Castor 
AudioAudio
Creative Sound Blaster X-Fi Titanium HD DT 990 Premium 250Ohm 
  hide details  
Reply
Just a 'puter
(18 items)
 
  
CPUMotherboardGraphicsRAM
Intel Core i7 6700K ASUS Maximus VIII Hero iGPU thanks to Nvidia 970 3.5GB Corsair Vengeance LPX CMK8GX4M2B3200C16 
Hard DriveHard DriveCoolingCooling
Samsung 950 PRO 512GB Crucial M4 256GB RX360 V3 Koolance CPU-380I 
CoolingCoolingOSMonitor
Koolance RP-452X2 Reservoir Koolance PMP-450 12V Variable Speed Pump Windows 10 Pro x64 benq XL2411Z 
KeyboardPowerCaseMouse
logitech G510 Seasonic X-760 Corsair 800D Mionix Castor 
AudioAudio
Creative Sound Blaster X-Fi Titanium HD DT 990 Premium 250Ohm 
  hide details  
Reply
New Posts  All Forums:Forum Nav:
  Return Home
  Back to Forum: Intel CPUs
Overclock.net › Forums › Intel › Intel CPUs › What does vccsa and vccio actually do?