Overclock.net - An Overclocking Community - View Single Post - Skylake-X/Kaby Lake-X Combined Discussion

View Single Post
post #9731 of (permalink) Old 03-18-2019, 01:39 PM
Jpmboy
OC...D
 
Jpmboy's Avatar
 
Join Date: Apr 2012
Location: Philadelphia
Posts: 26,296
Rep: 1273 (Unique: 561)
Quote: Originally Posted by RichKnecht View Post
A quick question. I know what LLC is and what it does. However, say I can run a particular OC at 1.22V and a LLC level of 6. Now, that same overclock can be achieved by raising VCore to 1.225 and lowering LLC to 5. From what I am seeing, the setting with higher vcore but lower LLC seems to run cooler in all benchmarks. Does this make sense, or am I imagining things?
THere's two ways to look at LLC on any voltage rail it is implemented on. The thing you are trying to control is call a Load Line Transient.
From a durability perspective, LLC is there to mitigate V_ovs. V_ovs is the inherent overshoot (milli sec) that occurs when you abruptly change the current flow on any voltage-clamped circuit (eg, VCCIN on x299). At stock settings the spec is somewhere around 50mV normal op, 200mV virus-mode (eg, heavy stability testing). The LLC-permitted droop creates a compensation window/margin for the overshoot that mitigates (most or some of) V_ovs ABOVE what you set as the voltage in bios. So, when running these HEDT chips at an average overclock (what, +20%) you can expect occasional vccin excursions in the higher mV range, especially when doing things like 995 - tho new VRs control this much better than than before. It's a current-based effect, this is why you see more droop at high(er) current loads.
The other way to look at this is LLC also lets you compensate for the inherent undershoot (it's a oscillation around the set value) by starting at a higher voltage before vdroop... ever have a very cpu-intensive benchmark fail right when the bench ends? That's from undershoot. It's a balance.
Basically, IMO, for a 24/7 system, it is s good idea to allow for some "healthy" amount of droop of the rail LLC is acting on (VCCIN or vcore). Extreme benchmarking is different, and undershoot is the concern. In my experience (even in most benchmarks) I've never really experienced a scenario where it is better to meet voltage requirements with LLC increases (eg, lowering vdroop) than by simply increasing the voltage setting and allowing vdroop. In many implementations, LLC simply adds voltage to the value you set in bios... that's the wrong way to use LLC, IMO.
In the pics below, "vdroop" is labeled as "offset" in the early days. These are from socket 775 - when LLC settings were first made available in bios.
Attached Thumbnails
Click image for larger version

Name:	transient_no_vdroop.jpg
Views:	4
Size:	49.1 KB
ID:	259984  

Click image for larger version

Name:	transient_no_vdroop_no_offset.jpg
Views:	4
Size:	48.2 KB
ID:	259986  


ASUS Z370/Z390 Motherboard Support Thread, Coffee Lake OC Guide
GPUs For Sale
X299
(27 items)
x99
(18 items)
Z370
(19 items)
CPU
7980XE
CPU
7740X
CPU
9900X
Motherboard
ASUS Rampage VI Apex
Motherboard
Gigabyte Aorus G9
Motherboard
Rampage VI Extreme Omega
GPU
2x Nvidia Titan V
GPU
GTX 1080
GPU
2 2080Ti FE / EK Vector Blocks
RAM
G. Skill 2x(2x8GB) 3600c15 @4000c16
RAM
Team Group
RAM
Two 4x8GB GS 3600c16 kits @ 4000c16
Hard Drive
INtel Optane 900P
Hard Drive
2x256 Plextor Raid 0
Hard Drive
WD Raptor
Hard Drive
Samsung Sm 961
Power Supply
Corsair AX1500i
Power Supply
EVGA 850 G3
Cooling
Aquacomputer GiGant 1680 (4x420)
Cooling
Koolance EXC-800
Case
Microcool Banchetto 101 (Alu)
Case
Corsair 570X
Operating System
Win 10 Pro
Operating System
Win 7 Pro
Monitor
ROG Swift
Keyboard
Ducky
Mouse
Spatha
CPU
6950X
Motherboard
ASUS Rampage V Extreme-10
GPU
Titan Xp
GPU
Titan Xp
RAM
G Skill 8x8GB 3200c14 @3400c13
Hard Drive
Samsung 960 Pro
Optical Drive
ASUS BR/DVD/CD
Power Supply
Corsair AX1500i
Cooling
2x360 Aq Copper Rads
Cooling
Aquaero 6
Cooling
Koolance ERM-3K3U (9-fan mora)
Cooling
Ek Full Cover MB waterblock
Case
CaseLabs Mercury S8
Operating System
Win 10 Pro
Operating System
Win 7 Pro
Monitor
AGON 32 inch
Keyboard
Das Pro
Mouse
Logitech G700
CPU
8700K
CPU
8086K
Motherboard
ASUS Maximus X Apex
GPU
GTX 1070Ti FTW2
RAM
2x8 GB G.Skill 4400c19
RAM
G.Skill 3600c16 4x6GB
Hard Drive
Intel 750
Optical Drive
PLextor DVD/CD
Power Supply
Corsair AX1500i
Power Supply
Corsair HX 1200i
Power Supply
Seasonic Titanium 850W
Cooling
360Rad + Chiller
Cooling
Koolance ERM-3K3U
Case
Corasir 570
Operating System
Win 10
Operating System
Windows 7 Pro
Monitor
55" 4K
Keyboard
HyperX Alloy FPS Pro
Mouse
SteelSeries Rival
▲ hide details ▲



Last edited by Jpmboy; 03-18-2019 at 01:52 PM.
Jpmboy is offline