overclocking through multiplier, HT , or both

[sabah70]

I have only overclocked to date using either the multiplier or the HT. To our OC pros, what do you guys do and how do you decide what to change when. I would really like to pick your brains. Thinking about doing something with hwbot but not sure where to start.

[Korth]

Quick and dirty version:

Read every OC guide you can find, especially those specific to your motherboard, CPU, GPU, etc. Also read product reviews about your stuff, since many of them touch upon overclocking and comment about the results/settings they used. These days there are literally hundreds of fine control/tweaking options in an enthusiast EUFI/BIOS, with millivolt and milliamp and nanosecond precision, but few of us actually know what the hell most of these things really do. In some instances some obscure settings are deliberately cryptic and undocumented because the mobo maker doesn't want to give the competition an edge by sharing the fruits of their own testing/engineering/research. There's essentially a half-dozen or so settings and voltages you need to change to gain fine control of all but the most extreme overclock.

Focus on one part at a time, CPU or RAM kit (or even individual RAM sticks) or one GPU. Don't try to masterfully overclock everything together until you know the thresholds for each component. RAM is a bit tricky (especially with the 4- or 8-stick kits) because there's often one or two borderline weaklings which hold the rest of the sticks down. Be aware that any given CPU can have a range of clock speeds for each core and for each uncore component (most significantly the integrated memory controller, because the iMC will govern maximum RAM capacity/speeds). GPUs are easier to overclock, up to their voltage-locked limits, so long as you can keep them cool and a multi-GPU setup isn't crippled by a slowpoke card. Always start at the bottom and slowly nudge things up, don't attempt to start at 5GHz and work downwards unless you like the smell of burnt silicon (which, I promise, is a smell you will never forget).

These days, almost every part can be overclocked unless it has fully locked-down clocks/multipliers/voltages/etc. To make it run more stable you often need to increment input power/voltage levels, very reluctantly, because this outputs more heat (and strains the part). You need a robust PSU, mobo, and cooling system to get good overclocks, not to mention the overclocked part itself (which is variable and quirky from part to part, ie: "the silicon lottery"). Most parts gain steady performance increases with little additional input voltage, but eventually reach a point where voltages/temps begin to rise exponentially for each further increment in performance, and most parts can actually run at insanely faster speeds with exotic/subzero cooling (which is how the LN2 guys achieve world-class record-breaking OC scores) but in the real world will have a maximum stable overclock dictated by the "sweet spot" between how much (or preferably, how little) voltage you feed in and how much heat your cooler can pull out.

A comprehensive overclocking process requires numerous restarts and, at some point, numerous frustrating (alarmingly sudden) crashes and shutdowns. Many people online (even at these ROG forums) wonder why they get BSoDs or memory errors or all sorts of oddball hardware failures on a daily basis ... in the vast majority of cases it's because they overclocked too high, beyond the stability threshold of their particular parts. No part operated at factory rated spec is ever 100% stable (although at least the manufacturer will replace a really bad part with another), and parts operated outside spec (overclocked) are certainly never 100% stable either. It's up to you how far you wanna push, how hot you're willing to run, performance vs stability. And, by the way, an overclock which works on certain settings today may not work on the same settings tomorrow, it can be hard on the parts and you just never know. Your system might be "perfectly stable" for many hours before an over-overclock crash/problem manifests itself, it's part of the process.

I always snapshot the default factory UEFI/BIOS settings for all my parts. Then let the mobo-integrated overclocking tools do their thing and snapshot the "optimized" UEFI/BIOS settings they've selected (which are, after all, based on years of research and the collective input of world-class overclockers). These settings are great reference baselines to build upon. I don't seriously expect to be able to do better than all the mobo engineers, specialists, and overclocking leaders - the variances in my individual parts likely fall within their statistical patterns - but nobody (me or them) really knows what the exact thresholds are until they have been tried and tested and measured, so it's usually possible to squeeze a little bit more performance if done manually.

[sabah70]

korth thanks for the reply. I have read a ton of guides but always looking to learn. the one thing I never see a consensus on is multiplier vs fsb. i think i said ht link in the title but fsb would have been more accurate. For example I want to oc my cpu but leave memory stock can i do that if I use fsb or northbridge? or will i just be able to get it close. Will performance gains be better on fsb or is it negligible? have not found any thing concrete in the research so I was asking opinions.

[Korth]

Increasing the base clock (BCLK, etc) forces all the interconnected parts - basically everything on the mobo - to run at the higher base frequency. Because so many (complex) parts are involved, there is a lower chance that everything will run stable (if at all) at higher BCLKs, even with lower multipliers. In general, since a higher BCLK makes everything faster the overall overclock will be faster. In reality, lower (stock) BCLKs with higher multipliers are what most of us have to do, and while overall motherboard speed might be less the speed of the specific parts which matter most (namely, the CPU and RAM) can reach their maximum potentials.

And 4.5GHz is always faster than 4.0GHz, no matter how the numbers are juggled.

The main issue these days is processors which have weak iMCs. I had an i7-5960X like this, it could overclock up to 4.7GHz on air with 4x4GB DDR4-2133, or it could run at (stock) 3.0GHz with 8x8GB DDR4-3000 - I chose a balancing point on my overclocks where it could run 3.5GHz with 8x8GB DDR4-2666. (All DDR4-3000 DIMMs, sometimes operating at lower frequencies for stability. Memory performance is more of a bottleneck than processor performance, for the sorts of things I do.)

[sabah70]

interesting. I think that was the issue with my 8350. I had it a oced to 4.8 using abase clock of 225 plus the multipler. it overclocked the ram to 1800 and I never changed the voltage. I'm thinking that was the reason for shut downs. today I put the base back to 200 and am doing 4.8 for a few days to see what happens also put the ht and northbridge to 2200 on both although i believe the ht stock is 2600 on my chip any way we'll see what happens. it's all a learning experience for me. looking to move from a casual overclocker to up a bit so any knowledge i get from you all is a blessing.

korth are most of your overclocks done with stock multipliers? also what would you consider a high bclk?

[sabah70]

interesting. I think that was the issue with my 8350. I had it a oced to 4.8 using abase clock of 225 plus the multipler. it overclocked the ram to 1800 and I never changed the voltage. I'm thinking that was the reason for shut downs. today I put the base back to 200 and am doing 4.8 for a few days to see what happens also put the ht and northbridge to 2200 on both although i believe the ht stock is 2600 on my chip any way we'll see what happens. it's all a learning experience for me. looking to move from a casual overclocker to up a bit so any knowledge i get from you all is a blessing.

[elesde]

On AM3+ FSB (HT ref) OC is mostly used to fine tune mem/NB clocks once a stable OC range has been found for the CPU. Sometimes also for overclocking with turbo but since you can set P-states manually via Overdrive or PSCheck it is not necessary.

As always in these threads I like to post the OC.net AM3+ guide for ASUS boards, helped me a lot 😄
http://www.overclock.net/t/1348623/amd-bulldozer-and-piledriver-overclocking-guide-asus-motherboard

[sabah70]

thanks I have not seen this one you have been most helpful