Haswell Overclocking

[aaronking]

It has been years since I upgraded my PC, and I've just started trying to re-educate myself as I look towards another purchase.

I have a question about overclocking the Haswell CPUs. I read somewhere that only the 'k' models can be overclocked. Is this true and if so, why?

Also, is it possible to overclock using an H87 board, or must it be a Z87?

Sorry for the newbie type questions. Just trying to get my bearings here.

Thanks,

 

[TerryMathews]

Must be a K, and must be a Z87.

Why? Intel's greedy.

 

[BSim500]

I have a question about overclocking the Haswell CPUs. I read somewhere that only the 'k' models can be overclocked. Is this true and if so, why?

It's generally best to get a Z87 board as you get better control over voltages, etc. And yes, you need a K to overclock. Since Haswell, Intel removed the +400Mhz limited OC feature previously available on Sandy & Ivy Bridge CPU's:-

i5-3470 Ivy = 3.2GHz Base can be OC'd to 3.8-4.0GHz (3.4-3.6GHz Turbo + 400MHz)
i5-4570 Has = 3.2GHz Base can only Turbo to 3.4-3.6GHz

i5-3570 Ivy = 3.4GHz Base can be OC'd to 4.0-4.2GHz (3.6-3.8GHz Turbo + 400MHz)
i5-4670 Has = 3.4GHz Base can only Turbo to 3.6-3.8GHz

 

[aaronking]

Just to be clear, are you saying that non 'K' models can't even be overclocked by raising the FSB on the Mobo? I assume the 'k' allows for the multiplier to be changed.

 

[ShintaiDK]

Just to be clear, are you saying that non 'K' models can't even be overclocked by raising the FSB on the Mobo? I assume the 'k' allows for the multiplier to be changed.

There is no such thing as FSB anymore. Its a BLCK clock, but that gets unstable rather fast. You need Z series chipset and K model CPU.

 

[BSim500]

Just to be clear, are you saying that non 'K' models can't even be overclocked by raising the FSB on the Mobo? I assume the 'k' allows for the multiplier to be changed.

From what I've read, the "BCLK gearing" thing is only available on K chips (which is stupid since they need it the least). You could squeeze about +170MHz performance on a 3.4GHz base by raising the BCLK to 105MHz at the risk of instability / "silent errors", but ever since Sandy Bridge, Intel's are not like raising the FSB of old 1st-gen Clarkdale's, etc, where you OC an i3-530 to +4GHz on BCLK alone. The only way to seriously OC modern Intel's is to buy a K chip. Or if you wanted a mild 4.0-4.2GHz OC on the cheap, you could pick up an Ivy Bridge i5 3470/3570 if you can find one on offer (but that still needs a Z77 board, it won't work with a H77).

Edit: Yes "K" means unlocked multiplier. The BCLK is still essentially set at 100Mhz on all.

 

[aaronking]

Wow...things have really changed. Thanks.

 

[Cerb]

I have a question about overclocking the Haswell CPUs. I read somewhere that only the 'k' models can be overclocked. Is this true and if so, why?

The FSB is gone. RAM talks directly to the CPU, now, and the CPU typically has some PCIe lanes coming off it, so some of your add-on cards also talk directly to the CPU. All but some Xeons have IGP right on the CPU, too. Moore's Law made us all kinds of crazy. Intel locked multipliers a long time ago, and now practically locked the rest of it.

Also, is it possible to overclock using an H87 board, or must it be a Z87?

Probably? My B85 board has OC options, but I got a Xeon (like an i7, but priced for us cheap bastards ), so all I can really do with them is lower my Turbo speed . What happened was someone found a way around the Z chipset limitation, I think ASRock, and implemented non-Z OC in other boards. Then, Intel went, "uh, no, we're going to put a stop to this." I'm not sure if there's ever been a firm resolution, but once Intel said they were going to stop it, most people assumed they'd do it, and stopped trying to save $30 (news from awhile back).

Sorry for the newbie type questions. Just trying to get my bearings here.

If you missed the 2008 "Nehalem" generation CPUs from Intel, you missed out on some major changes. Changes since have been typical generational changes. But, the new CPUs in late 2008 had them following AMD in features from a few years before, and one-upping them overall.

The end result has been that, if you're going to OC, you need to plan for it from day one. The days of getting an OK CPU and seeing what it's capable of just by adding a $30 cooler to a decent stock rig are over with.

 

[BonzaiDuck]

Since Haswell, Intel removed the +400Mhz limited OC feature previously available on Sandy & Ivy Bridge CPU's:-

I never heard anything about "+400Mhz limited OC feature." I'm still running a Sandy Bridge 2600K. If the stock turbo speed was 3.8Ghz, and my OC turbo-speed is 4.6Ghz, there's no "400Mhz limit."

 

[Homeles]

I never heard anything about "+400Mhz limited OC feature." I'm still running a Sandy Bridge 2600K. If the stock turbo speed was 3.8Ghz, and my OC turbo-speed is 4.6Ghz, there's no "400Mhz limit."

Non-K Sandy and Ivy chips had a form of limited turbo bin overclocking. That went away with Haswell.

 

[BonzaiDuck]

Non-K Sandy and Ivy chips had a form of limited turbo bin overclocking. That went away with Haswell.

Sorry -- my mistake. You are correct, and provide useful information.

I never bothered with the locked CPUs. Sooner or later, I may have to, if the fam-damn-ily wants to trade in their Wolfdale systems for IB or Haswell. But they don't seem to be in a big rush . . .

 

[ali1988]

Yes you need a K series chip and Z87. Don't even touch the Bclk or you're asking for trouble. It's multiplier only these days.

One big change is that the oc you get on the cpu is not so dependent on the motherboard anymore. This is because the memory controller is now integrated (IMC) and now in haswell, so too is the VRM for the CPU. This allows super precise control (0.001v) of vcore and nice clean stable power to cpu, rendering all the fancy 12 phase power of high end boards kinda useless from an OC perspective.

 

[BSim500]

I never heard anything about "+400Mhz limited OC feature." I'm still running a Sandy Bridge 2600K. If the stock turbo speed was 3.8Ghz, and my OC turbo-speed is 4.6Ghz, there's no "400Mhz limit."

"K" chips are fully unlocked so it doesn't apply to yours anyway. The most common overclocking fallacy over the past few years is that any i5/i7 chip which wasn't a "K" was as fully locked down as i3's. In reality, Intel permitted a +400MHz limited OC feature on Sandy & Ivy Bridge chips that was very useful in that it guaranteed the slowest i5's were not slower than the cheaper fastest i3's for 1-2 threaded tasks, eg, i5-3350P max Turbo is only 3.3GHz but can be OC'd to 3.7GHz on a Z motherboard to make sure it isn't slower than a cheaper i3-3240/3250 at 3.4-3.5GHz for single threaded tasks.

Anandtech did a full article on it here in their first Sandy Bridge review:-
http://www.anandtech.com/show/4083/...-core-i7-2600k-i5-2500k-core-i3-2100-tested/3

Sadly, they've removed that +400Mhz feature from Haswell non-K's ending up with low-end i5 chips which are now not only far less cost effective than i3's for 1-2 threaded tasks but can even run slower than i3's clocked 300-400MHz faster in some games, not to mention making it completely pointless to "upgrade" from a 4.2GHz i5-3570 to a 3.8GHz i5-4670...

 

[Homeles]

Sorry -- my mistake. You are correct, and provide useful information.

I never bothered with the locked CPUs. Sooner or later, I may have to, if the fam-damn-ily wants to trade in their Wolfdale systems for IB or Haswell. But they don't seem to be in a big rush . . .

If they leave their systems on all the time, Haswell's reduced idle power would be great. Heck, even something that's just power gated (Nehalem or later from Intel; Llano/Zambezi or later from AMD).

A more efficient PSU can also save quite a bit over its lifetime.

 

[BonzaiDuck]

If they leave their systems on all the time, Haswell's reduced idle power would be great. Heck, even something that's just power gated (Nehalem or later from Intel; Llano/Zambezi or later from AMD).

A more efficient PSU can also save quite a bit over its lifetime.

We've got all these systems (four workstations and a WHS server [E8400] set up to sleep -- excluding the server. I don't bother with the latter, because I store a lot of DVR files on it, and I sleep like a retired person-- waking when I want, and watching TV when I want.

The key to making this work has obviously been good power supplies. When I discovered problems with the sleep-state on one LGA775 Wolfdale system, I realized it used a now-9-year-old OCZ Powerstream. I replaced it with a Seasonic, and the troubles disappeared.