[Strix z370-F] Help needed to get my RAM stable at 2666MHz (or 2800MHz if possible)

[Wolfdale]

Hello guys!
That's my first post here on the RoG forum so I'm really hoping that I'm not doing anything wrong. I'm having troubles setting my RAM to anything higher than 2400MHz although it supports 2 XMP profiles - one at 2800MHz 14-15-15-39 and one at 2666MHz 14-14-14-36. Here's a list of my components:

1. PSU Corsair RM 750
2. MB Strix z370-F updated to BIOS 0419
3. 4x 8GB Kingston HyperX Savage - half of this kit of 8x 8GB.
4. CPU i7-8700k de-lidded with Thermal Grizzly Conductonaut under the IHS
5. Custom water cooling with an EKWB Supremacy Evo block and an Alphacool Nexxxos UT60 rad (360x60 mm)

I'm trying to get my PC stable at 5GHz and I'm testing with Prime 95 v26.6 (non-AVX). I'm using 'Manual' settings in UEFI (instead of XMP) and I deciced to do the clocking step by step. First I wanted to see the max frequency I can get from the CPU, then I wanted to buff my RAM and third - increase CPU Cache (Uncore) as much as I can. With RAM set to 2400MHz at 14-14-14-36-2N (fairly low, just to get it out of my way) I was able to reach 5GHz stable at 1.328v on the CPU and I mean really stable - I'm able to run 12+ hours of Prime 95 v26.6 stress-testing. The problem is that once I tried to set my RAM to 2600MHz at 14-14-14-36-2N I immediately got stability issues. Prime 95 started to produce errors in 20 to 60 minutes. I also tried 2666 at 14-14-14-36-2N and 2800 at 14-15-15-39-2N without any luck. It seems that any RAM settings above 2400MHz are causing stability issues, although the RAM is rated to support 2800MHz at 14-15-15-39-2N and 2666MHz at 14-14-14-36-2N. My system is stable at 2400MHz RAM with 0.95v VCCIO and 1.05 System Agent. I've tried upping those up to 1.20v (for both of them) but I couldn't get my RAM stable at anything higher than 2400MHz.

Could you please tell me what I'm doing wrong here? Obviously my RAM is supposed to be capable for 2800MHz at 14-15-15-39 and also it's part of a 8x 8GB kit which means all the sticks are tested together for Quad-Channel setups. On z370 we are talking of just 4 sticks at Dual Channel so why is it failing? For some reason I'm not even able to use the 2666MHz speed specified by XMP Profile #2. I'm attaching a full set of my UEFI settings here. Also I'd like to mention that enabling XMP as a method of overclocking (instead of Manual) isn't working any better either. The system can easily boot at 2666 14-14-14-36-2N or 2800 14-15-15-15-39-2N, but once I start testing with Prime95 the worker threads just start crashing in less than an hour. My Uncore is set at 4200MHz. If you need more information - please feel free to ask 🙂

[ZooLz8l]

this might not help you much but, I have ram that has an xmp profile for 4000mhz but I can only get it stable at 3600. and I know of a few people who have similar problems. so not getting the full speed on ram seems to be a thing with the z370 boards.

[Wolfdale]

ZooLz8l wrote:
this might not help you much but, I have ram that has an xmp profile for 4000mhz but I can only get it stable at 3600. and I know of a few people who have similar problems. so not getting the full speed on ram seems to be a thing with the z370 boards.

Well, the thing is that 4000MHz is not supported officially anyway at least. The 8700k's integrated memory controller is capable of DDR4-2666MHz according to Intel's specs so it's kind of acceptable that you are only able to push it to 3600. In my case, however, I'm trying to reach at least 2666MHz which is well within the specs of the CPU memory controller 🙂

Raja@ASUS wrote:
Can you run a higher memory speed at a lower CPU frequency? If so, at 5GHz you'll need to tune SA/IO voltage and perhaps even CPU Vcore. Depends how on the edge the CPU is at the applied overclock.

Hm... I haven't tried that. Sadly I'm already at work with no access to the PC, but I'll check that too once I get home. I've always thought that Vcore is just for Cores and Cache and that System Agent is supposed to feed the Memory Controller. But neither SA nor the IO made any difference up to 1.20v as already stated. Out of curiosity - what are the 'safe' values for those voltages? And what is the VCCIO feeding? Anyway, I'll check later if I can push the RAM at 2666MHz by lowering the CPU frequency to 4800MHz and report back. I guess 200mhz lower should be enough (by using the current VCore).

[Raja]

Wolfdale wrote:


Hm... I haven't tried that. Sadly I'm already at work with no access to the PC, but I'll check that too once I get home. I've always thought that Vcore is just for Cores and Cache and that System Agent is supposed to feed the Memory Controller. But neither SA nor the IO made any difference up to 1.20v as already stated. Out of curiosity - what are the 'safe' values for those voltages? And what is the VCCIO feeding? Anyway, I'll check later if I can push the RAM at 2666MHz by lowering the CPU frequency to 4800MHz and report back. I guess 200mhz lower should be enough (by using the current VCore).

In simple terms, you're increasing throughput over the bus as you overclock the CPU, which can sometimes require higher voltage for all associated domains. Especially on this platform, as the uncore is fed from CPU Vcore.

AS for SA and IO, I usually go up to 1.30V or so (if needed). Given the mem clock, you shouldn't need that much, though.

[Raja]

Wolfdale wrote:
Hello guys!
That's my first post here on the RoG forum so I'm really hoping that I'm not doing anything wrong. I'm having troubles setting my RAM to anything higher than 2400MHz although it supports 2 XMP profiles - one at 2800MHz 14-15-15-39 and one at 2666MHz 14-14-14-36. Here's a list of my components:

1. PSU Corsair RM 750
2. MB Strix z370-F updated to BIOS 0419
3. 4x 8GB Kingston HyperX Savage - half of this kit of 8x 8GB.
4. CPU i7-8700k de-lidded with Thermal Grizzly Conductonaut under the IHS
5. Custom water cooling with an EKWB Supremacy Evo block and an Alphacool Nexxxos UT60 rad (360x60 mm)

I'm trying to get my PC stable at 5GHz and I'm testing with Prime 95 v26.6 (non-AVX). I'm using 'Manual' settings in UEFI (instead of XMP) and I deciced to do the clocking step by step. First I wanted to see the max frequency I can get from the CPU, then I wanted to buff my RAM and third - increase CPU Cache (Uncore) as much as I can. With RAM set to 2400MHz at 14-14-14-36-2N (fairly low, just to get it out of my way) I was able to reach 5GHz stable at 1.328v on the CPU and I mean really stable - I'm able to run 12+ hours of Prime 95 v26.6 stress-testing. The problem is that once I tried to set my RAM to 2600MHz at 14-14-14-36-2N I immediately got stability issues. Prime 95 started to produce errors in 20 to 60 minutes. I also tried 2666 at 14-14-14-36-2N and 2800 at 14-15-15-39-2N without any luck. It seems that any RAM settings above 2400MHz are causing stability issues, although the RAM is rated to support 2800MHz at 14-15-15-39-2N and 2666MHz at 14-14-14-36-2N. My system is stable at 2400MHz RAM with 0.95v VCCIO and 1.05 System Agent. I've tried upping those up to 1.20v (for both of them) but I couldn't get my RAM stable at anything higher than 2400MHz.

Could you please tell me what I'm doing wrong here? Obviously my RAM is supposed to be capable for 2800MHz at 14-15-15-39 and also it's part of a 8x 8GB kit which means all the sticks are tested together for Quad-Channel setups. On z370 we are talking of just 4 sticks at Dual Channel so why is it failing? For some reason I'm not even able to use the 2666MHz speed specified by XMP Profile #2. I'm attaching a full set of my UEFI settings here. Also I'd like to mention that enabling XMP as a method of overclocking (instead of Manual) isn't working any better either. The system can easily boot at 2666 14-14-14-36-2N or 2800 14-15-15-15-39-2N, but once I start testing with Prime95 the worker threads just start crashing in less than an hour. My Uncore is set at 4200MHz. If you need more information - please feel free to ask 🙂

Can you run a higher memory speed at a lower CPU frequency? If so, at 5GHz you'll need to tune SA/IO voltage and perhaps even CPU Vcore. Depends how on the edge the CPU is at the applied overclock.

[Wolfdale]

Raja@ASUS wrote:
Can you run a higher memory speed at a lower CPU frequency? If so, at 5GHz you'll need to tune SA/IO voltage and perhaps even CPU Vcore. Depends how on the edge the CPU is at the applied overclock.

Seems like lowering the frequency didn't help at all. I backed off a good 300MHz from the Core Clock and only tried the lower XMP profile (2666MHz). And Prime95 failed in less than half an hour. I also upped both VCCIO & SA by 0.05 reaching 1.00v for IO and 1.10v for SA but it's still failing. Is my RAM defective? Or simply not compatible? The memory controller of 8700k natively supports DDR4-2666, so I'm not even overclocking the memory, obviously. Pretty frustrating at this point. Is my RAM faulty? Is it 'okay', but simply not fully compatible with this platform? I guess everyone knows how much the RAM prices increased recently and I don't feel like buying a whole new 32GB kit just for testing. 😞

Edit: Tried IO & SA to 1.237v. Again failed after ~40 minutes. 😞

[Raja]

Wolfdale wrote:
Seems like lowering the frequency didn't help at all. I backed off a good 300MHz from the Core Clock and only tried the lower XMP profile (2666MHz). And Prime95 failed in less than half an hour. I also upped both VCCIO & SA by 0.05 reaching 1.00v for IO and 1.10v for SA but it's still failing. Is my RAM defective? Or simply not compatible? The memory controller of 8700k natively supports DDR4-2666, so I'm not even overclocking the memory, obviously. Pretty frustrating at this point. Is my RAM faulty? Is it 'okay', but simply not fully compatible with this platform? I guess everyone knows how much the RAM prices increased recently and I don't feel like buying a whole new 32GB kit just for testing. 😞

Edit: Tried IO & SA to 1.237v. Again failed after ~40 minutes. 😞

Difficult to say. You can try relaxing the memory timings by adding +1 to CAS and tRCD and see if that makes a difference. Or you can up the DRAM voltage somewhat. That kit may not be stable without some manual tuning.