Do all PC's report so much RAM missing?
evanh
Posts: 15,916
I just did a search as to why my Linux box isn't reporting the full amount of RAM installed - 7.8GB instead of 8GB. And one of the links that came up was this one - http://superuser.com/questions/154422/ubuntu-10-4-64-bit-os-8gb-ram-is-shown-as-7-8gb-why
It's a well worded straight forward question, covering exactly my question, but, given it should affect everyone, very little effort seems to have been made to even confirm it.
The answer about binary vs decimal scaling is way off the mark and can only be plain wrong. RAM is always manufactured in powers of two. Besides, his calculations are pretty twisted and thoughtless.
The data structures answer only applies to used, not total, memory. So that wasn't very thoughtful either. The integrated graphics idea, with unified memory, was reasonable but discounted.
So that leaves the negatively mod'ed answer of PCI allocations causing remapping losses or something, not sure how this is meant to pan out.
Anyone have knowledge on this? Maybe it's just Linux? Can anyone confirm if Windoze gives same result?
It's a well worded straight forward question, covering exactly my question, but, given it should affect everyone, very little effort seems to have been made to even confirm it.
The answer about binary vs decimal scaling is way off the mark and can only be plain wrong. RAM is always manufactured in powers of two. Besides, his calculations are pretty twisted and thoughtless.
The data structures answer only applies to used, not total, memory. So that wasn't very thoughtful either. The integrated graphics idea, with unified memory, was reasonable but discounted.
So that leaves the negatively mod'ed answer of PCI allocations causing remapping losses or something, not sure how this is meant to pan out.
Anyone have knowledge on this? Maybe it's just Linux? Can anyone confirm if Windoze gives same result?
Comments
Wow, and I see the rubbish story about binary vs decimal scaling is very active too. There's not much thinking going on!
So reserved space for an unused integrated GPU is definitely not it.
8192 - 256 = 7936 MB.
Reported total RAM is 7984.45 MB. So 207.55 MB missing.
2GB is just 47.44 MB missing.
4GB is 143.55 MB missing.
6GB is 175.54 MB missing.
Which explains why it hasn't been talked about at smaller amounts. The 4GB point was always considered messy due to it's 32bit limit issue. The 2GB point may have been noticed but ignored for being too small.
(N x 16 + 79.55) MB. Where N = amount of installed RAM in GB.
So a 16GB system will appear to be missing 16 x 16 + 79.55 = 335.55 MB.
And 32GB system will be missing 591.55 MB!
The question is about total memory, not free memory.
Eg:
$ free total used free shared buffers cached Mem: 8176076 1601452 6574624 36144 78024 645612 -/+ buffers/cache: 877816 7298260 Swap: 0 0 0It's that reported total of 8176076 kB, which is my earlier reported 7984.45 MB.There is always 1 MB missing there. I'd be more than happy if the OS was reporting just 1 MB missing too.
This utility shows I have 8091.7890625MB RAM, so on Windows it appears as though task manager rounds down. Task manager shows 8091 MB.
That is strange...
Isn't that the difference between megabytes and mebibytes?
All numbers are given in original binary scale.
What does Win10 report? I note Xanadu is reporting 8091.79MB, which is 100.21MB missing. Not the same result as me but still significant.
That's been clearly discounted multiple times. The final one being that the amount missing depends on the amount of RAM installed.
I only listed my card as part of the details because that is an example of a situation where the behaviour is still occurring even when there is no hardware or BIOS programmed to handle integrated GPU. If the OS was maintaining reservation for a non-existent device, that wouldn't be very smart.
It's OK
Mike
I thought linux shows MiB and not MB?
8GB = 8192 MB = 7812.5 MiB.
I'll speculate the reason for the losses scaling up with increasing total RAM installed will be due to a fixed total number of blocks that are scaled up in proportion to the total RAM. Only fully mapped blocks can be safely relocated, and therefore every largely isolated small PCI mapping will consume a whole block that can't be relocated. As the block size increases so does the losses.
Windows 10 "msinfo32.exe" reports 4.0GB installed / total. 64 bit Win10 by the way.
On board Intel G33 video is disabled in BIOS.
ATI 5450 PCIe video card installed- that has 512MB DDR3 memory; Windows' DXDIAG reports 4096MB system ram.
So all my ram is present and accounted for. Puzzling.
Just looking at a Windoze 7 box while I'm at work and the [Control Panel -> System] window is telling me 2.00 GB is installed but importantly, in brackets, it also says 1.87 GB usable. So, 0.13 GB -> 133.12+ MB is missing.
That's a terrible result for a 2GB system except, in this case, it is also using its integrated GPU. So, a chunk of that, maybe 64MB, will be reserved for GPU private operations.
Installed Physical Memory (RAM) 2.00 GB
Total Physical Memory 1.87 GB
Which obviously matches my first attempt with the control panel.
Abecedarian,
Are you saying you get 4.0GB reported on both lines?
I'd be very surprised if that was truly possible given what I've seen so far. I suppose the real figure could be down as low as 10MB and Windoze is just rounding it off. That would still be a nice outcome though.
Motherboard is P5K-VM operating as 64 bit with C2Q Q8200 processor.
Motherboard web page is here.