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Old 07-11-2020, 01:25 PM   #1
Topcat
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Default Dell 960 Memory Allocation

I've seen a few Dell's do this....but here's the issue. This is a Optiplex 960. Note the RAM amount in the image below:



I ASSumed this 'usable' amount was taking into consideration memory grabbed by the onboard GPU....ok, no biggie. Here's where it gets goofy... I've put a PCIe GPU in this system, which presumably disables the onboard (no longer shows in device manager)...why has the memory not been released; IE the full 4GB usable? I have an Optiplex 980 doing the same thing except with 8gb; 7.87gb usable....very different platforms. BIOS's are latest/current.
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Old 07-11-2020, 03:54 PM   #2
Curious.George
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Default Re: Dell 960 Memory Allocation

Quote:
Originally Posted by Topcat View Post
I ASSumed this 'usable' amount was taking into consideration memory grabbed by the onboard GPU....ok, no biggie. Here's where it gets goofy... I've put a PCIe GPU in this system, which presumably disables the onboard (no longer shows in device manager)...why has the memory not been released; IE the full 4GB usable? I have an Optiplex 980 doing the same thing except with 8gb; 7.87gb usable....very different platforms. BIOS's are latest/current.
Disclaimer: I know nothing of how PC's work -- but a shitload about processors, in general!

[Presumably, you are running a 64b OS? Otherwise, you k now the total memory space will be limited to 4G... which must include the GPU memory]

If the CPU (chip) in the device can only address 4GB of PHYSICAL memory (i.e., if there are only 32 address lines leaving the processor), AND if the GPUs memory ends up directly mapped into the CPUs physical address space, then it consumes a portion of the ADDRESS space even if there exists other physical memory available (it "overlays" that memory).

You can test this by removing the GPU and installing some generic video adapter (with less memory) and manually disabling the onboard to see what it reports as usable in that configuration.

In the second machine, it could be that it has the capacity to address 8GB of physical memory and the GPUs memory is overlaying some portion of that.

[Again, reread my disclaimer]
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Old 07-11-2020, 04:25 PM   #3
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Default Re: Dell 960 Memory Allocation

Well, good thing is that you're running 64-bit Win7, so at least that takes the address space limitation out of the picture.

It looks like about 128MB is being reserved for some reason. Usually it depends on the BIOS and firmware memory mapping, sometimes SMM eats up RAM, sometimes BIOS shadow eats the RAM. As RAM amounts go up, that 128MB won't get "missed" with the RAM used up by the OS with stuff like pagetables,... so much for fleecing us.

Would be nice to get E820 data from the machine to know the exact memory map...
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Old 07-11-2020, 04:34 PM   #4
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Default Re: Dell 960 Memory Allocation

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Originally Posted by eccerr0r View Post
Well, good thing is that you're running 64-bit Win7, so at least that takes the address space limitation out of the picture.
No, it only takes the OS's address space constraints out of the picture. If only 32 address lines are bonded out of the chip, then the limitation would persist in the HARDWARE.

I assume that such bondout options are common (cost savings and feature restrictions) cuz, otherwise, why have an *8G* limit on a machine?
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Old 07-11-2020, 06:39 PM   #5
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Default Re: Dell 960 Memory Allocation

Some boards have different memory remap options in the BIOS, I guess for the limited BIOS in a Dell that is not an option though.
Here is a very lengthy MS article I found, it goes into quite some details about what can cause it.
My bet would still be that the built in graphics steals it, since it is such a nice round number missing.
Their specific mention of a Intel 975X is interesting though, I guess a Google search for your chipset might reveal something?

https://support.microsoft.com/en-us/...on-windows-7-b
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Old 07-11-2020, 06:41 PM   #6
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Default Re: Dell 960 Memory Allocation

Quote:
Originally Posted by Curious.George View Post
No, it only takes the OS's address space constraints out of the picture. If only 32 address lines are bonded out of the chip, then the limitation would persist in the HARDWARE.

I assume that such bondout options are common (cost savings and feature restrictions) cuz, otherwise, why have an *8G* limit on a machine?
It does not work that way, bus widths above 8-bit CPU's are pretty arbitrary.
64-bit vs 32-bit is a logic thing, not hardware.
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Old 07-11-2020, 06:45 PM   #7
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Default Re: Dell 960 Memory Allocation

Quote:
Originally Posted by Per Hansson View Post
Some boards have different memory remap options in the BIOS, I guess for the limited BIOS in a Dell that is not an option though.
Here is a very lengthy MS article I found, it goes into quite some details about what can cause it.
My bet would still be that the built in graphics steals it, since it is such a nice round number missing.
Their specific mention of a Intel 975X is interesting though, I guess a Google search for your chipset might reveal something?

https://support.microsoft.com/en-us/...on-windows-7-b
...as per my original post & thought....I just figured the BIOS would let it go when the onboard GPU disables. Strange but not the end of the world.
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Old 07-11-2020, 06:45 PM   #8
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Default Re: Dell 960 Memory Allocation

It's only 4 GB of RAM, FFS and it's acting like it's 32-bit!

Core 2, definitely supports at least 8 GB, if not more!
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Old 07-11-2020, 06:52 PM   #9
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Default Re: Dell 960 Memory Allocation

Actually a 32-bit processor, chipset that doesn't really support 4GB RAM, or 32-bit OS without PAE turned on running on 4GB RAM should show up near 3372MB RAM, this is even more than 512MB off from 4GB, so this is a different issue.
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Old 07-11-2020, 06:56 PM   #10
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Default Re: Dell 960 Memory Allocation

Quote:
Originally Posted by Topcat View Post
...as per my original post & thought....I just figured the BIOS would let it go when the onboard GPU disables. Strange but not the end of the world.
Yes, but my point was more that crap BIOS often have these limitations.
The memory does need to be remapped.
And older chipsets like that often have a 36-bit address bus in the memory controller.
That means a max of 8GB memory, but that includes stuff like the PCI address space, and memory on a dedicated GPU.
It all has to fit into the same address space...
Newer chipsets do not have these limitations.
And no, in your case it is of course not the 36-bit limitation.
But still, try it with 8GB and see what happens, it might reveal something.
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Old 07-11-2020, 07:16 PM   #11
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Default Re: Dell 960 Memory Allocation

Quote:
Originally Posted by Per Hansson View Post
That means a max of 8GB memory
For DDR2, you're lucky to get 8 GB when you raise VDIMM to 1.90V to run them at 333 Mhz (666/667) Because with consumer RAM, usually need to mix sticks and use all 4 slots!
Good luck with getting more than 8 GB of RAM with most DDR2 platforms.....

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Old 07-11-2020, 07:18 PM   #12
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Default Re: Dell 960 Memory Allocation

i think ratdude or dan87 had this problem before several years ago and they posted about it here too. my stand is still the same back then as it is now. i think its the 32-bit pci address space problem like with the gart table like per hansson said. thats why the memory hole still sticks even with a discrete gpu. some asus boards have a bios option to remap the 32-bit pci address space above 4gb to fix this type of issue and have the full 4gb usable, so its dell's crap bios at work.

i also did some memory benchmarking with the pci address space remapped. having the memory remap feature ON made memory latency slower by 1 ns. complete non-issue in real world applications and not noticeable at all. what is noticeable is the system being faster with more ram available when using memory hungry programs that gobble ram like skittles... just posting this for informational purposes in case someone is curious if the feature affects memory performance and why would u turn it off? lol.
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Old 07-11-2020, 07:43 PM   #13
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Default Re: Dell 960 Memory Allocation

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Originally Posted by RJARRRPCGP View Post
Good luck with getting more than 8 GB of RAM with most DDR2 platforms.....
I have plenty of DDR2 rigs running well above 8gb ram.
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Old 07-11-2020, 09:49 PM   #14
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Default Re: Dell 960 Memory Allocation

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Originally Posted by Per Hansson View Post
It does not work that way, bus widths above 8-bit CPU's are pretty arbitrary.
64-bit vs 32-bit is a logic thing, not hardware.
Huh? Who mentioned 8-bit CPUs?

And, 64 vs 32b is definitely a "hardware thing". A 32b OS is limited to a 32b logical address space simply because it (by definition) can't deal with pointers larger than 32b.

As an example, i3 westmere can only access 8G while sandybridge can do 16G and (most) skylakes can do 64G (though some are limited to 32G). The software doesn't "see" any difference between the "address space" available to each; rather, the hardware imposes those limitations.

They're all 64b processors. The LOGICAL address space in each of them is the same -- 2^64 bytes. Yet, if I try to access 195 billion different physical addresses, I will be sorely disappointed in each case -- despite the fact that the physical address space is 1,000,000,000 times larger than my "needs". Software (bare metal) needs to know the characteristics of the actual hosting processor AT RUN TIME in order to know how big it's actual physical address space is, for THIS processor.
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Old 07-12-2020, 01:54 AM   #15
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Default Re: Dell 960 Memory Allocation

it might actually be a sucky bios that still allocates 128M for video

or check your cmos to init on PCI-E and not IGP. Or see if it still is using the IGP in combination with the GPU for some reason
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Old 07-12-2020, 05:01 AM   #16
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Default Re: Dell 960 Memory Allocation

Quote:
Originally Posted by Curious.George View Post
No, it only takes the OS's address space constraints out of the picture. If only 32 address lines are bonded out of the chip, then the limitation would persist in the HARDWARE.

I assume that such bondout options are common (cost savings and feature restrictions) cuz, otherwise, why have an *8G* limit on a machine?
Quote:
Originally Posted by Per Hansson View Post
It does not work that way, bus widths above 8-bit CPU's are pretty arbitrary.
64-bit vs 32-bit is a logic thing, not hardware.
Quote:
Originally Posted by Curious.George View Post
Huh? Who mentioned 8-bit CPUs?

And, 64 vs 32b is definitely a "hardware thing". A 32b OS is limited to a 32b logical address space simply because it (by definition) can't deal with pointers larger than 32b.

As an example, i3 westmere can only access 8G while sandybridge can do 16G and (most) skylakes can do 64G (though some are limited to 32G). The software doesn't "see" any difference between the "address space" available to each; rather, the hardware imposes those limitations.

They're all 64b processors. The LOGICAL address space in each of them is the same -- 2^64 bytes. Yet, if I try to access 195 billion different physical addresses, I will be sorely disappointed in each case -- despite the fact that the physical address space is 1,000,000,000 times larger than my "needs". Software (bare metal) needs to know the characteristics of the actual hosting processor AT RUN TIME in order to know how big it's actual physical address space is, for THIS processor.
I inferred (perhaps incorrectly) that you meant physical address lines from your first post:
"If only 32 address lines are bonded out of the chip, then the limitation would persist in the HARDWARE."
That is why I made the example to an 8-bit CPU, because it is easy to visualize the 8 address lines in it.

Last edited by Per Hansson; 07-12-2020 at 05:16 AM..
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Old 07-12-2020, 11:57 AM   #17
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Default Re: Dell 960 Memory Allocation

I tried clearing the CMOS on the 960 & 980...no avail....still sucks up that 128mb needlessly. On a 380, when adding a PCIe GPU, the 128mb RAM is released by the BIOS, full amount (4 or 8gb) is available to the OS.
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Old 07-12-2020, 12:27 PM   #18
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Default Re: Dell 960 Memory Allocation

Quote:
Originally Posted by Topcat View Post
I tried clearing the CMOS on the 960 & 980...no avail....still sucks up that 128mb needlessly. On a 380, when adding a PCIe GPU, the 128mb RAM is released by the BIOS, full amount (4 or 8gb) is available to the OS.
plug a separate monitor in the IGP while it's on. If it outputs to the monitor, then the IGP is still enabled. might not be able to fully turn it off. Maybe there is a multi-monitor option that needs to be disabled, and the option to disable it might not be there
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Old 07-12-2020, 02:54 PM   #19
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Default Re: Dell 960 Memory Allocation

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Originally Posted by Topcat View Post
I have plenty of DDR2 rigs running well above 8gb ram.
That's because you have "server-class" and "pro-workstation-class" motherboards and thus, they can use that semi-ad-hoc-DDR2-SDRAM. (With ECC and buffering or the like)

Regular-consumer-class-DDR2-SDRAM=There's no more than 2 GB per stick or they are rare!

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Old 07-12-2020, 03:43 PM   #20
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Default Re: Dell 960 Memory Allocation

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Regular-consumer-class-DDR2-SDRAM=There's no more than 2 GB per stick or they are rare!
When chipsets of that era in that market don't support more than 8gb @ 4 slots w/ 2gb modules, was there really any demand for larger modules?
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