My specs:
Gigabyte G1 Gaming GTX 980 SLI.
Core i5-3570k (OC to @ 4.2 GHz, auto voltage).
16 GB of G.Skill Ripjaw-X DDR3 1600Mhz (x.m.p profile)
Asus Sabertooth Z77 Motherboard
SSD 256GB Crucial M4.
HD Western Digital Black 2TB
PSU: Corsair 850AX Gold
CPU Cooler: Noctua NH-D14
Case: Corsair CC600T Graphite White Special Edition
Win 8.1 64bit. Pro
Monitor: Asus ROG SWIFT PG278Q 2560 x 1440p 144 MHz
Secondary Screen: 55" TV: Samsung UA55D6400 TV1080p 60 MHz (TV Connected via Pioneer VSX-823-K AV Receiver)
I am considering overclocking my two Gigabyte GTX 980s G1s.
Both GPUs are rather new (7m, 1m old).
So I want to find a solid, stable and safe OC without increasing the voltage levels.
I looked it up, and found this guide:
http://www.guru3d.com/articles_pages/gigabyte_geforce_gtx_980_g1_gaming_review,26.html
As you can see the editor did add some extra Voltage.
I want to find a similar OC without adding any voltage to stay safe for long term use.
This is what I experimented now:

I tried playing some The Witcher 3 @ 1440p and mostly Ultra settings:
The game ran fine for a few hours yesterday, today it froze my entire PC but not sure if it's OC related at all.
My temps were very cool, around the 60s, and around 68-71c when over 95% load for a long time.
But the freeze still worries me.
Maybe I went overboard with the memory clock?
I know some people add +170 MHz Core Clock without adding voltage, but I don't know about Memory clocks.
Can/should I OC any further? like +500MHz memory or +170MHz Core? Or should I actually go down a notch or not OC at all?
Thanks in advance.
Gigabyte G1 Gaming GTX 980 SLI.
Core i5-3570k (OC to @ 4.2 GHz, auto voltage).
16 GB of G.Skill Ripjaw-X DDR3 1600Mhz (x.m.p profile)
Asus Sabertooth Z77 Motherboard
SSD 256GB Crucial M4.
HD Western Digital Black 2TB
PSU: Corsair 850AX Gold
CPU Cooler: Noctua NH-D14
Case: Corsair CC600T Graphite White Special Edition
Win 8.1 64bit. Pro
Monitor: Asus ROG SWIFT PG278Q 2560 x 1440p 144 MHz
Secondary Screen: 55" TV: Samsung UA55D6400 TV1080p 60 MHz (TV Connected via Pioneer VSX-823-K AV Receiver)
I am considering overclocking my two Gigabyte GTX 980s G1s.
Both GPUs are rather new (7m, 1m old).
So I want to find a solid, stable and safe OC without increasing the voltage levels.
I looked it up, and found this guide:
http://www.guru3d.com/articles_pages/gigabyte_geforce_gtx_980_g1_gaming_review,26.html
As you can see the editor did add some extra Voltage.
I want to find a similar OC without adding any voltage to stay safe for long term use.
This is what I experimented now:

I tried playing some The Witcher 3 @ 1440p and mostly Ultra settings:
The game ran fine for a few hours yesterday, today it froze my entire PC but not sure if it's OC related at all.
My temps were very cool, around the 60s, and around 68-71c when over 95% load for a long time.
But the freeze still worries me.
Maybe I went overboard with the memory clock?
I know some people add +170 MHz Core Clock without adding voltage, but I don't know about Memory clocks.
Can/should I OC any further? like +500MHz memory or +170MHz Core? Or should I actually go down a notch or not OC at all?
Thanks in advance.