DRAM issues on 9900K and Asus Z390-E

EclipseVV

EclipseVV

EclipseVV

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8 Nov 2020
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Hi just RMA'd my 9900K that worked perfectly for 6 months on a Z390-E Gaming due to several WHEA warnings appearing recently in the Event Log; Intel troubleshooted this as a defective CPU. The CPU was working fine otherwise, and my DRAM was working fine with VCCIO/VCCSA set at 1.15 with 3333MHz sticks.

However, as soon as I tried another 9900K, something worse happened: the new CPU seems to work only with really high VCCIO/VCCSA voltages, at least 1.35V/1.40V (that's what the board automatically set up after a few unsuccessful reboots). As soon as I try something lower (even at stock 2666MHz), I get hundreds of errors in all DRAM test programs.

I also tried with other DRAM sticks and the situation is unchanged.

What would you recommend? This sound again like a defective CPU / IMC, but it still seems quite strange... could it be a motherboard issue?

The CPU itself with small FFT tests is 100% stable. The issue is with DRAM access only.
 
Yes, absolutely. I also tried the previous one, no difference.

It also seems quite picky with DRAM speed/timings: VCCIO 1.325 VCCSA 1.375 is stable at 3500MHz, but not at 2666, 3200 or 3600 (with DDR-3600 sticks and identical timings). Tested with Karhu and 2000% coverage.

VCCIO 1.30 VCCSA 1.35 is not stable at every speed I tested (with identical timings).

It took several hours to find one setup that actually worked: all XMP/JEDEC profiles do not work!

Basically, I passed my whole sunday testing the DDR-3600 XMP timings (17-19-19-39), and lowering frequency:
- 3600MHz: not stable at 1.35/1.40 or lower
- 3500MHz: stable at 1.325/1.375
- 3200Mhz: not stable at 1.35/1.40 or lower
- 2666MHz: not stable at 1.35/1.40 and auto voltages

I decided not to try raising VCCSA above 1.40 for fear or destroying my CPU.

Not stable = error almost immediately with Karhu (below 100% coverage).

Can you recommend something else, or do I need to RMA again? And in that case, CPU or MB?
 
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Having a second faulty cpu would be unlikely but not impossible, otherwise it may be the motherboard .

Have you checked for miss aligned pins on the motherboard
 
When the mother board goes in to self learning for the voltage (constant reboot till if finds a working combination) can be that the overclock is too high but there's another way that this can happen... If it's set to overclock by AI in the Bois (automatic overclocking).

Never use this function I've had my cpu voltage automatically set to 1.6v with crazy memory control voltage.
 
Pins seemed to be fine when I mounted the second CPU, but I cannot exclude it 100%.

The CPU itself is on pretty normal vcore values, and on CPU-only tests (Prime95, Linpack, OCCT small, etc) there are zero errors.

What puzzles me is that raising VCCIO/VCCSA everything works for certains speeds (I started another Karhu Ram Test a few hours ago and I'm at 3000% coverage with no errors). That would seem to rule out motherboard... or not?
 
When you have such weird problems it's hard to diagnose, but you've replaced the cpu and tried diffrent ram. That leaves the motherboard not performing normally, why I'm not sure but motherboards are complex.
 
A quick update: on monday I decided to RMA the second 9900K and mounted the new one a few hours ago: the new CPU seems to be stable with DRAM at 3600MHz (XMP profile without any adjustment) and DRAM = 1.35V, VCCIO = 1.225V, VCCSA = 1.200V.

So, indeed, it seems I had two defective CPUs in a row. The VCCIO/VCCSA seems a bit on the high side for 3600 (or not?), but I'd say I can use these voltages and enjoy my PC :)
 
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