doveman

16GB installed, only 12GB usable in Win7 x64 Ultimate

36 posts in this topic

I installed an extra 8GB the other day and it was all showing as usable in Windows 7 x64 Ultimate then. Today I noticed only 12GB was showing in HwInfo, so I checked the System properties and that showed 16GB installed, 12GB usable.

So I rebooted and checked the BIOS and that shows 16GB. I changed it from 1600Mhz to 1333mhz and rebooted in Windows and now it shows the entire 16GB as usable. It's Corsair Vengeance LP DDR3, which is specified to work at 1600Mhz at 1.5v. CPU-Z shows JEDEC#4 as 666Mhz@1.5v and XMP-1600@1.5v. I've left the Voltage and timings in the BIOS on Auto.

I actually just had one 2*4GB kit replaced as one of the sticks went bad and the other I just bought so that I could use the PC whilst I was waiting for the original kit to be replaced, so I hope another stick hasn't gone bad!

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which motherboard do you use? Does it support Memory remapping? is this enabled in the BIOS? Have you used MSconfig to limit the max usable RAM?

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It's a MSI 990FXA-GD80. Haven't noticed any option for Memory remapping in the BIOS (it doesn't have onboard IGP if that's relevant) and I haven't used MSconfig either. As I say, the whole 16GB is usable in Windows if I set it to 1333Mhz in the BIOS but I'd like to run it at the specified 1600Mhz and I don't see why one stick should be unusable at that speed whilst the other three work fine.

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Memory remapping = memory hoisting. Your BIOS has it or else you'd never see the 16 GiB as usable, whatever the frequency.

It's a MSI 990FXA-GD80. Haven't noticed any option for Memory remapping in the BIOS (it doesn't have onboard IGP if that's relevant) and I haven't used MSconfig either. As I say, the whole 16GB is usable in Windows if I set it to 1333Mhz in the BIOS but I'd like to run it at the specified 1600Mhz and I don't see why one stick should be unusable at that speed whilst the other three work fine.

I bet your machine got nothing wrong but, despite the manufacturer's claims, it's northbridge simply cannot control that much RAM that fast, so it skips part of it. When you set the RAM a little less fast, however, then it's able to cope with all of it. Set it again to 1600 MHz... do 4 GiB diappear? Return it to 1600 MHz... do all 16 GiB get detected once again?

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I bet your machine got nothing wrong but, despite the manufacturer's claims, it's northbridge simply cannot control that much RAM that fast, so it skips part of it. When you set the RAM a little less fast, however, then it's able to cope with all of it. Set it again to 1600 MHz... do 4 GiB diappear? Return it to 1600 MHz... do all 16 GiB get detected once again?

Wouldn't surprise me. Manufacturer's always obfuscate about the capabilities of their boards :rolleyes:

I'll test as you suggest but just want to be clarify that from the tests I already did the BIOS detects all 16GB at 1600Mhz or 1333Mhz, as does Windows but 4GB of it is unusable in Windows at 1600Mhz, whereas it's all usable at 1333Mhz.

If I can't run it at 1600Mhz, should I still be able to overclock the NB to 2600Mhz as I did when running with only 8GB? That would help make up for it. In fact, when I tested before that made more difference, although obviously ideally I'd be able to run both the RAM at 1600Mhz and the NB at 2600Mhz.

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I'll test as you suggest but just want to be clarify that from the tests I already did the BIOS detects all 16GB at 1600Mhz or 1333Mhz, as does Windows but 4GB of it is unusable in Windows at 1600Mhz, whereas it's all usable at 1333Mhz.

That tells one that Windows Memory Control is tighter than the one done by the BIOS, but that's just what's expected, anyway.

If I can't run it at 1600Mhz, should I still be able to overclock the NB to 2600Mhz as I did when running with only 8GB? That would help make up for it. In fact, when I tested before that made more difference, although obviously ideally I'd be able to run both the RAM at 1600Mhz and the NB at 2600Mhz.

The only way to know for sure is by testing.

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I'll test as you suggest but just want to be clarify that from the tests I already did the BIOS detects all 16GB at 1600Mhz or 1333Mhz, as does Windows but 4GB of it is unusable in Windows at 1600Mhz, whereas it's all usable at 1333Mhz.

That tells one that Windows Memory Control is tighter than the one done by the BIOS, but that's just what's expected, anyway.

If I can't run it at 1600Mhz, should I still be able to overclock the NB to 2600Mhz as I did when running with only 8GB? That would help make up for it. In fact, when I tested before that made more difference, although obviously ideally I'd be able to run both the RAM at 1600Mhz and the NB at 2600Mhz.

The only way to know for sure is by testing.

OK, thanks.

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This "practical" misadventure :( of doveman does raise (at least it raises to me) a couple philosophical or theoretical questions :w00t: (open to everybody):

  1. WHAT is the need for 16 GB? <--"absolute" question
  2. WHICH is "better" (i.e. faster/more useful/advisable)? (12 Gb@1600Mhz or 16 Gb@1333Mhz) <--"relative question"

and a third one coming purely from curiosity :ph34r: (aimed to doveman only):

  • WHAT the heck are you running on that machine that *somehow* prompted you to decide that the previous 8 GB were not enough?

jaclaz

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This "practical" misadventure :( of doveman does raise (at least it raises to me) a couple philosophical or theoretical questions :w00t: (open to everybody):

  1. WHAT is the need for 16 GB? <--"absolute" question
  2. WHICH is "better" (i.e. faster/more useful/advisable)? (12 Gb@1600Mhz or 16 Gb@1333Mhz) <--"relative question"

and a third one coming purely from curiosity :ph34r: (aimed to doveman only):

  • WHAT the heck are you running on that machine that *somehow* prompted you to decide that the previous 8 GB were not enough?

jaclaz

Well the third question is addressed in my first post :whistle: I had to buy another kit otherwise I wouldn't have been able to use my PC for two weeks whilst I was waiting for the original faulty kit to be exchanged. However, I also have a couple of experiments with running certain games from RAMdrive that I'm interested in trying to see if they eliminate some stuttering problems I'm experiencing with them and it's possible that DCS World, ArmA 3 and X-Plane 10 will be able to use more than 8GB in the near future (DCSW may already be able to as it's 64-bit). I probably wouldn't have bought another 8GB if I hadn't needed to though.

I can't answer your other questions but perhaps these benchmarks with 8GB I did a while ago will be of some use. Note I don't think I ever got it stable with the NB at 2600Mhz though, so settled for 2400Mhz.

DDR3-666 (1333) Mhz (9-9-9-24-1T), NB 2000Mhz:

Copy 10466 MB/s

Read 8107 MB/s

Write 6831 MB/s

Score 7.47GB/s

Latency 66.9 ns

---

DDR3-800 (1600) Mhz (9-9-9-24-1T), NB 2000Mhz

Copy 10560 MB/s

Read 8667 MB/s

Write 6734 MB/s

Score 7.70 GB/s

Latency 65.0 ns

---

DDR3-800 (1600) Mhz (9-9-9-24-1T), NB 2400Mhz

Copy 11602 MB/s

Read 9457 MB/s

Write 7883 MB/s

Score 8.67 GB/s

Latency 61.5 ns

---

DDR3-800 (1600) Mhz (9-9-9-24-1T), NB 2600Mhz, CPU-NB 1.32v, NB 1.3v

Copy 11867 MB/s

Read 9822 MB/s

Write 8457 MB/s

Score 9.14 GB/s

Latency 60.4 ns

---

DDR3-666 (1333) Mhz (9-9-9-24-1T), NB 2600Mhz, CPU-NB 1.32v, NB 1.3v

Copy 11350 MB/s

Read 9010 MB/s

Write 8583 MB/s

Score 8.80 GB/s

Latency 62.5 ns

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I can't answer your other questions but perhaps these benchmarks with 8GB I did a while ago will be of some use. <snip>

DDR3-666 (1333) Mhz (9-9-9-24-1T), NB 2000Mhz:

Copy 10466 MB/s

Read 8107 MB/s

Write 6831 MB/s

Score 7.47GB/s

Latency 66.9 ns

---

DDR3-800 (1600) Mhz (9-9-9-24-1T), NB 2000Mhz

Copy 10560 MB/s

Read 8667 MB/s

Write 6734 MB/s

Score 7.70 GB/s

Latency 65.0 ns

---

So, 1600 vs 1333 means:

Copy 0.9 % faster

Read 6.9 % faster

Write 1.4 % slower

Latency 2.8 % less

This "practical" misadventure :( of doveman does raise (at least it raises to me) a couple philosophical or theoretical questions :w00t: (open to everybody):

  1. WHAT is the need for 16 GB? <--"absolute" question
  2. WHICH is "better" (i.e. faster/more useful/advisable)? (12 Gb@1600Mhz or 16 Gb@1333Mhz) <--"relative question"

My replies to your questions:

1) None at all.

2) Since "faster" is almost imperceptible (see above: 7 % at most!), "more" is better (in the sense that there may be some rare occasion where all that memory may be actually filled, perhaps by running numerous virtual machines or the like). The benchmark above confirms it, but common sense alone should suffice to conclude that "more" is better than "faster", in this context, IMO.

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If the CPU you use has a C2 stepping, it will have a 667MHz (1333 DDR) Memory controller onboard, 1600 DDR will be out of spec. You could try to set the voltage of the Memory higher, that includes the memory controller voltage and terminations as well.

You would need to tweak it little by little to get the 16GB to work. BIOS update could help sometimes...

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So, 1600 vs 1333 means:

Copy 0.9 % faster

Read 6.9 % faster

Write 1.4 % faster

Latency 2.8 % less

Be aware of the math:

(10560/10466)-1=+0.9%

(8667/8107)-1=+6.91%

(6734/6831)-1=-1.42%

@doveman

Well no. :no:

If you have some "spare" 8 Gb testing them is OK, but nothing actually "prompts" or "forces" you to add it to an otherewise perfectly working machine with already 8 Gb (unless you use the machine with a few high end programs that need heaps of RAM).

jaclaz

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@doveman

Well no. :no:

If you have some "spare" 8 Gb testing them is OK, but nothing actually "prompts" or "forces" you to add it to an otherewise perfectly working machine with already 8 Gb (unless you use the machine with a few high end programs that need heaps of RAM)

As I've already explained (twice :whistle:) it wasn't a "perfectly working machine with already 8GB" as I had to send the 8GB back to get replaced as it was faulty, so I didn't "add" another 8GB to the existing 8GB, I bought 8GB so that I could continue to use the machine in the meantime, then put the other 8GB back in when I got the replacement kit. Sure I could sell one of the kits now but I'd make a loss so it seems rather pointless.

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If the CPU you use has a C2 stepping, it will have a 667MHz (1333 DDR) Memory controller onboard, 1600 DDR will be out of spec. You could try to set the voltage of the Memory higher, that includes the memory controller voltage and terminations as well.

You would need to tweak it little by little to get the 16GB to work. BIOS update could help sometimes...

CPU-Z shows that my Phenom II X4 955 has revision RB-C3. I'm aware that the spec doesn't officially support 1600 DDR though but as it worked with 8GB I was surprised to find it doesn't with 16GB. I'll look at tweaking the voltages to see if I can get it to work though, thanks.

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As I've already explained (twice :whistle:) it wasn't a "perfectly working machine with already 8GB" as I had to send the 8GB back to get replaced as it was faulty, so I didn't "add" another 8GB to the existing 8GB, I bought 8GB so that I could continue to use the machine in the meantime, then put the other 8GB back in when I got the replacement kit. Sure I could sell one of the kits now but I'd make a loss so it seems rather pointless.

Yep, and I have understood. :thumbup

The point I was trying to make is slightly different, more around the Occam's Razor approach:

http://en.wikipedia.org/wiki/Occam's_razor

With a "good" set of chips (8 Gb in total) does the machine work OK?

If yes, then do you have any benefit of any kind that you can actually measure/feel with adding to it the other "spare" 8?

If yes, then do it.

If not, keep the spare ones as "spare" (or give away them, or keep them for another machine you plan to buy).

It seems to me like there is NO actual difference (or at least one that you can actually perceive without using a benchmark) between:

  1. 8 Gb @1333 <- stable and working OK
  2. 8 Gb @1600 <- stable and working OK

but we know that:

  1. 16 Gb @1333 <- possibly stable and working OK but largely unused
  2. 16 Gb @1600 <- found UNstable and NOT working OK besides being largely unused

If you prefer, you have proven that 16 Gb@1600 is NOT good on that motherboard and - at the moment - found that by downclocking the RAM the machine works OK with 16 Gb @1333, but what actual practial advnatages do you have with 16GB@1333 over running 8Gb@1600?

If, as I presume, the answer is "None", the only use of that additional 8 Gb is to be able to tell your friends how powerful is your machine with 16 Gb and have a slightly increased power consumption and have the "spare" be worn out a bit. :w00t:

jaclaz

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