Question Bios Detects 32Gb when RAM running at half speed. But 16gb when I up their speed

Gorzul

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Mar 28, 2014
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Hello all,

I have 32gb of corsair RAMs, I noticed my windows10 is detecting 16gb, I went into bios was also 16gb, I had turned on XMP and set my RAMs at 1866mhz Speed earlier, or close to that (they are 2400mhz)
However when I do that, in fact when I change anything in my Bios at all, Bios only detects 16gb of RAM.
So The only way it detects 32gb, is if I leave everythign to optimal defaults, and the RAMs running at 1333Mhz which is half their speed.
Any idea what is causing this or how it can be fixed?

Thanks.

And here's my pc specs:
CPU: Intel i7-4820K LGA 2011 64 + Corsair Hydro Series Extreme Performance Liquid CPU Cooler H100i
Motherboard: ASUS P9X79 LGA 2011 Intel X79 SATA 6Gb/s USB 3.0 ATX Intel Motherboard
RAM: 32GB (8x4) Corsair Vengeance Pro 16GB 2x8GB DDR3 2400MHz PC3 19200 Desktop, Red CMY16GX3M2A2400C11R
GPU: ASUS ROG Swift 1080ti
HDD: SSD Samsung 1tb
PSU make and age: 4 years, Corsair Professional Series 860 Watt Digital ATX/EPS Modular 80 PLUS Platinum Power Supply AX860i (links to 1200w, but its 860W model)
Dual Monitors: ROG SWIFT PG278RQ(primary) + BenQ XL2411
OS: Windows 10
 
This is in no way definite answer but.. have you checked following:
Used CPU-Z to check all memory sticks reported speeds and latencies? if any of them differ from each other, it is quite likely that automated XMP will not work (as you have noticed)
tried setting said things yourself manually?
Latency: 11-13-13-31
Voltage: 1.65V (Notice, this is BIG overvoltage, these sticks NEED it to run at reported 2400MHZ) if standard 1.5, they will most likely work only up to lower frequencies.
If it still doesn't work, it is quite likely that since said sticks were sold as 2x8GB bundles, they were never tested to work as 2x2x8GB bundle of 4 sticks.

Many memory manufacturers recommend using ready made kits of X times Y that are sold as kits and those are pretty much only ones where manufacturer guarantees said sticks work together.

Edit: I would also point out that manufacturers qualified vendor list (meaning sticks they have TESTED to work for sure) is bit old and outdated and... stops at 16GB total.
 
Last edited:

Gorzul

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Mar 28, 2014
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This is in no way definite answer but.. have you checked following:
Used CPU-Z to check all memory sticks reported speeds and latencies? if any of them differ from each other, it is quite likely that automated XMP will not work (as you have noticed)
tried setting said things yourself manually?
Latency: 11-13-13-31
Voltage: 1.65V (Notice, this is BIG overvoltage, these sticks NEED it to run at reported 2400MHZ) if standard 1.5, they will most likely work only up to lower frequencies.
If it still doesn't work, it is quite likely that since said sticks were sold as 2x8GB bundles, they were never tested to work as 2x2x8GB bundle of 4 sticks.

Many memory manufacturers recommend using ready made kits of X times Y that are sold as kits and those are pretty much only ones where manufacturer guarantees said sticks work together.
Thanks for your reply mate.
I checked all 4 slots on CPU-Z, all 4 show the exact same values which is this http://prntscr.com/n03ar1 This is default running at 1333mhz. Which is the only way the Bios sees 32gb.
Would you still suggest I do it manually?

Also, could putting them in the wrong slots on the motherboard give such a result?
Cause putting them as per the manual recommendation was false, it did not show 32gb at all no matter what.
I ended up switching the modules to different slots and can now at least see 32gb.
 

Gorzul

Honorable
Mar 28, 2014
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This is in no way definite answer but.. have you checked following:
Used CPU-Z to check all memory sticks reported speeds and latencies? if any of them differ from each other, it is quite likely that automated XMP will not work (as you have noticed)
tried setting said things yourself manually?
Latency: 11-13-13-31
Voltage: 1.65V (Notice, this is BIG overvoltage, these sticks NEED it to run at reported 2400MHZ) if standard 1.5, they will most likely work only up to lower frequencies.
If it still doesn't work, it is quite likely that since said sticks were sold as 2x8GB bundles, they were never tested to work as 2x2x8GB bundle of 4 sticks.

Many memory manufacturers recommend using ready made kits of X times Y that are sold as kits and those are pretty much only ones where manufacturer guarantees said sticks work together.

Edit: I would also point out that manufacturers qualified vendor list (meaning sticks they have TESTED to work for sure) is bit old and outdated and... stops at 16GB total.
yeah just did the XMP profile which is the one you suggested. at 2400mhz windows10 wont load at all.
The only way is to set overclock to Manual, and set the Ram frequency to 1866mhz manually, thats the highest itll go while still being able to go into windows.
But when I do that the voltages and everything else goes back to default automatically and only 16gb are visible.
I can get bios/windows to see 32gb only if I set my bios to optimal defaults, in which case they run at 1333mhz.

So I guess no solution?
In that case would you say its better having 16gb running at 1866 or 32gb at 1333?

Thanks again for your help
 
Following is mostly guesswork after staring at motherboard manual, Qualified vendor lists and such.

Edit: Also as cin19's mentioned link says, check that you have latest BIOS, it could be critical for bigger/speedier memory configurations.

Yes, I would try setting them manually. Worst that happens is that computer refuses to boot and you would need to reset BIOS.
https://dlcdnets.asus.com/pub/ASUS/mb/LGA2011/P9X79/E8038_P9X79.pdf Edit2: This manual at least also lists ways to alter DRAM voltage, clockspeeds and timings.
So.. 4 dimms, in four channel mode. (Then again QVL shows that most often last two dimm slots (D1 and D2) are not recommended, not that it is a certain rule) and you can't really use triple channel RAM with 4 sticks, you could maybe do that with three and get 24GB?

or.. some parts of memory controller are just not quite working and that could explain why they wont show up at all. If that is the case, running it in dual channel setup (A1/2 and B1/2) with 2x8GB in both channels would be the next best option if it recognizes all at default SPD speed (666/1333Mhz)

CPU itself doesn't supposedly support speeds over 933/1866 though according to specs and XMP profile timings are for 1200/2400Mhz, making the setup past 1333 bit.. of a guesswork? (timings of XMP-2400 should still work as far as I know even at 1866 speed, provided the voltage can also be set at higher than 1.5V, this might require some extra bios setting being enabled to allow you to alter both voltage and clockspeeds and timings manually)

Also for the last question, 16GB at 1866 or 32GB at 1333, I would say it depends on ram amount you need If you don't use over 16GB normally, bigger speed is better, if you do (why else get 32GB?) more ram is better, personally I'd pick 32GB at lower speed.
 
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Use of multiple kits of memory have no guarantee to be compatible together. Memory is guaranteed in the form sold. Likewise XMP settings are also for memory in the form sold. Other combinations you decide to make have no guarantee as to how they will operate.

i7-4820K
Supported memory: DDR3-1066, DDR3-1333, DDR3-1600, DDR3-1866

Although higher speed memory may be beneficial when overclocking a "k" processor, you may need to lower memory clock speed to get multiple memory kits to work.
 

Gorzul

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Mar 28, 2014
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Following is mostly guesswork after staring at motherboard manual, Qualified vendor lists and such.

Edit: Also as cin19's mentioned link says, check that you have latest BIOS, it could be critical for bigger/speedier memory configurations.

Yes, I would try setting them manually. Worst that happens is that computer refuses to boot and you would need to reset BIOS.
https://dlcdnets.asus.com/pub/ASUS/mb/LGA2011/P9X79/E8038_P9X79.pdf Edit2: This manual at least also lists ways to alter DRAM voltage, clockspeeds and timings.
So.. 4 dimms, in four channel mode. (Then again QVL shows that most often last two dimm slots (D1 and D2) are not recommended, not that it is a certain rule) and you can't really use triple channel RAM with 4 sticks, you could maybe do that with three and get 24GB?

or.. some parts of memory controller are just not quite working and that could explain why they wont show up at all. If that is the case, running it in dual channel setup (A1/2 and B1/2) with 2x8GB in both channels would be the next best option if it recognizes all at default SPD speed (666/1333Mhz)

CPU itself doesn't supposedly support speeds over 933/1866 though according to specs and XMP profile timings are for 1200/2400Mhz, making the setup past 1333 bit.. of a guesswork? (timings of XMP-2400 should still work as far as I know even at 1866 speed, provided the voltage can also be set at higher than 1.5V, this might require some extra bios setting being enabled to allow you to alter both voltage and clockspeeds and timings manually)

Also for the last question, 16GB at 1866 or 32GB at 1333, I would say it depends on ram amount you need If you don't use over 16GB normally, bigger speed is better, if you do (why else get 32GB?) more ram is better, personally I'd pick 32GB at lower speed.
Thanks a lot for your help you're awesome.
Thank you everyone else also.
All this info is very helpful I'll get on it.
 

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