Re: why 1G memory is missing?

[Marco Möller]

On 03.08.21 18:26, IL Ka wrote:

inxi shows that only 3 GB are available as the TOTAL, although it finds
the 4 GB to be physically installed:
$ sudo inxi -m -x
Memory:    RAM: total: 2.88 GiB used: 2.11 GiB (73.2%)
Array-1: capacity: 4 GiB slots: 2 EC: None max module size: 2 GiB
note: est.
Device-1: M1 size: 2 GiB speed: 667 MT/s type: DDR2
Device-2: M2 size: 2 GiB speed: 667 MT/s type: DDR2


It could be a different problem (Windows may calculate RAM differently 
in different places, where did you check it?).
I'd start with a memory map (see Sven Hartge's comment in this thread), 
also see https://en.wikipedia.org/wiki/E820 


A similar tool for Windows is "Rammap".

With 32bit system you would never be able to use 4GB (because part of 
address space is used for MMIO by PCI-(express) devices).
With 64bit address space is much larger, but some ram is used by kernel. 
Some tools exclude such ram.




Although the original question got a valid answer already, in this case 
the chipset did not support 4 GB and not even a 64bit OS, I here add to 
some sub-part of the thread (see above in this email what I am referring 
to) some information for completeness - I got time to search in old 
threads on the German spoken Debian mailing list where this topic was 
also up some time ago.


Sven Hartge pointed out and explained that the missing 1 GB on a 64 bit 
system could be related to what is called the "PCI hole" and also the 
following link was provided:


https://en.wikipedia.org/wiki/PCI_hole

I wasn't able to understand all technical explanations by Sven Hartge, 
neither everything what's published in the wikipedia article, this all 
is obviously a topic for real hardware experts, but it at least 
convinced me that it should not be a configuration failure in my Debian 
installation - however, why MS Windows on the identical hardware shows 
the full 4 GB to be available never became clear to me.


Saying all this, I will not be able to further discuss this topic here 
in this thread as I am for far too large extend not understanding the 
necessary basics, but at least wanted to leave this information about 
the "PCI hole".


Always stay in good spirits, Marco!

Re: why 1G memory is missing?

[Jeremy Hendricks]

Yup. That too.

On Tue, Aug 3, 2021 at 7:42 PM IL Ka  wrote:

>
>> That cpu was normally paired with the Intel 945 chipset that can’t
>> support more than about 3.25GB whether or not it’s 32/64 OS
>>
>
> Yes, and even worse: this CPU doesn't support 64bit OS
>
>> model name   : Intel(R) Atom(TM) CPU N280   @ 1.66GHz
>>> address sizes   : 32 bits physical, 32 bits virtual
>>>
>>>
> https://ark.intel.com/content/www/us/en/ark/products/41411/intel-atom-processor-n280-512k-cache-1-66-ghz-667-mhz-fsb.html
>  Instruction Set: 32-bit
>
>

Re: why 1G memory is missing?

[IL Ka]

>
>
> That cpu was normally paired with the Intel 945 chipset that can’t support
> more than about 3.25GB whether or not it’s 32/64 OS
>

Yes, and even worse: this CPU doesn't support 64bit OS

> model name: Intel(R) Atom(TM) CPU N280   @ 1.66GHz
>> address sizes: 32 bits physical, 32 bits virtual
>>
>>
https://ark.intel.com/content/www/us/en/ark/products/41411/intel-atom-processor-n280-512k-cache-1-66-ghz-667-mhz-fsb.html
 Instruction Set: 32-bit

Re: why 1G memory is missing?

[Jeremy Hendricks]

That cpu was normally paired with the Intel 945 chipset that can’t support
more than about 3.25GB whether or not it’s 32/64 OS

On Tue, Aug 3, 2021 at 7:24 PM  wrote:

> Thank Andy! my cpu is 32bit
> i have thought pae can support more than 4G memory
> but in fact it can't use full 4G memory hardware
>
> $ cat /proc/cpuinfo
> processor : 0
> vendor_id : GenuineIntel
> cpu family: 6
> model : 28
> model name: Intel(R) Atom(TM) CPU N280   @ 1.66GHz
> stepping  : 2
> microcode : 0x218
> cpu MHz   : 1000.000
> cache size: 512 KB
> physical id   : 0
> siblings  : 2
> core id   : 0
> cpu cores : 1
> apicid: 0
> initial apicid: 0
> fdiv_bug  : no
> f00f_bug  : no
> coma_bug  : no
> fpu   : yes
> fpu_exception : yes
> cpuid level   : 10
> wp: yes
> flags : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov 
> pat clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe nx constant_tsc 
> arch_perfmon pebs bts aperfmperf pni dtes64 monitor ds_cpl est tm2 ssse3 xtpr 
> pdcm movbe lahf_lm dtherm
> bugs  :
> bogomips  : 3325.02
> clflush size  : 64
> cache_alignment   : 64
> address sizes : 32 bits physical, 32 bits virtual
> power management:
>
> processor : 1
> vendor_id : GenuineIntel
> cpu family: 6
> model : 28
> model name: Intel(R) Atom(TM) CPU N280   @ 1.66GHz
> stepping  : 2
> microcode : 0x218
> cpu MHz   : 1667.000
> cache size: 512 KB
> physical id   : 0
> siblings  : 2
> core id   : 0
> cpu cores : 1
> apicid: 1
> initial apicid: 1
> fdiv_bug  : no
> f00f_bug  : no
> coma_bug  : no
> fpu   : yes
> fpu_exception : yes
> cpuid level   : 10
> wp: yes
> flags : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov 
> pat clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe nx constant_tsc 
> arch_perfmon pebs bts aperfmperf pni dtes64 monitor ds_cpl est tm2 ssse3 xtpr 
> pdcm movbe lahf_lm dtherm
> bugs  :
> bogomips  : 3325.02
> clflush size  : 64
> cache_alignment   : 64
> address sizes : 32 bits physical, 32 bits virtual
> power management:
>
>
>
>

Re: why 1G memory is missing?

[loushanguan2015]

Thank Andy! my cpu is 32bit 
i have thought pae can support more than 4G memorybut in fact it can't use full 
4G memory hardware

$ cat /proc/cpuinfo
processor   : 0
vendor_id   : GenuineIntel
cpu family  : 6
model   : 28
model name  : Intel(R) Atom(TM) CPU N280   @ 1.66GHz
stepping: 2
microcode   : 0x218
cpu MHz : 1000.000
cache size  : 512 KB
physical id : 0
siblings: 2
core id : 0
cpu cores   : 1
apicid  : 0
initial apicid  : 0
fdiv_bug: no
f00f_bug: no
coma_bug: no
fpu : yes
fpu_exception   : yes
cpuid level : 10
wp  : yes
flags   : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov 
pat clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe nx constant_tsc 
arch_perfmon pebs bts aperfmperf pni dtes64 monitor ds_cpl est tm2 ssse3 xtpr 
pdcm movbe lahf_lm dtherm
bugs:
bogomips: 3325.02
clflush size: 64
cache_alignment : 64
address sizes   : 32 bits physical, 32 bits virtual
power management:

processor   : 1
vendor_id   : GenuineIntel
cpu family  : 6
model   : 28
model name  : Intel(R) Atom(TM) CPU N280   @ 1.66GHz
stepping: 2
microcode   : 0x218
cpu MHz : 1667.000
cache size  : 512 KB
physical id : 0
siblings: 2
core id : 0
cpu cores   : 1
apicid  : 1
initial apicid  : 1
fdiv_bug: no
f00f_bug: no
coma_bug: no
fpu : yes
fpu_exception   : yes
cpuid level : 10
wp  : yes
flags   : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov 
pat clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe nx constant_tsc 
arch_perfmon pebs bts aperfmperf pni dtes64 monitor ds_cpl est tm2 ssse3 xtpr 
pdcm movbe lahf_lm dtherm
bugs:
bogomips: 3325.02
clflush size: 64
cache_alignment : 64
address sizes   : 32 bits physical, 32 bits virtual
power management:

Re: why 1G memory is missing?

[IL Ka]

>
> inxi shows that only 3 GB are available as the TOTAL, although it finds
> the 4 GB to be physically installed:
> $ sudo inxi -m -x
> Memory:RAM: total: 2.88 GiB used: 2.11 GiB (73.2%)
> Array-1: capacity: 4 GiB slots: 2 EC: None max module size: 2 GiB note:
> est.
> Device-1: M1 size: 2 GiB speed: 667 MT/s type: DDR2
> Device-2: M2 size: 2 GiB speed: 667 MT/s type: DDR2
>
>
It could be a different problem (Windows may calculate RAM differently in
different places, where did you check it?).
I'd start with a memory map (see Sven Hartge's comment in this thread),
also see https://en.wikipedia.org/wiki/E820
A similar tool for Windows is "Rammap".

With 32bit system you would never be able to use 4GB (because part of
address space is used for MMIO by PCI-(express) devices).
With 64bit address space is much larger, but some ram is used by kernel.
Some tools exclude such ram.

Re: why 1G memory is missing?

[Marco Möller]

On 03.08.21 00:42, IL Ka wrote:


i have 2 memory slots
memtest86+ shows each has 2G, but total is 3G
after booting linux, top shows total is 3G

why 1 G is missing? Thanks!



You probably have 32bit OS
https://en.wikipedia.org/wiki/3_GB_barrier 





Not as easy. I have this same problem on two hardware systems.
Using a 64bit Debian OS, installed to an USB-Stick and then booted on 
different hardware fully uses the 8 GB in one equipment physically 
providing 8 GB RAM, but in two other systems only 3 GB out of physically 
present 4 GB RAM are used by DEBIAN. MS Windows is using all the 4 GB, 
and doing this without any changes in the BIOS.


uname shows that a 64 bit OS is in use:
Linux XX 5.10.0-8-amd64 #1 SMP Debian 5.10.46-3 (2021-07-28) x86_64 
GNU/Linux


inxi shows that only 3 GB are available as the TOTAL, although it finds 
the 4 GB to be physically installed:

$ sudo inxi -m -x
Memory:RAM: total: 2.88 GiB used: 2.11 GiB (73.2%)
Array-1: capacity: 4 GiB slots: 2 EC: None max module size: 2 GiB note: est.
Device-1: M1 size: 2 GiB speed: 667 MT/s type: DDR2
Device-2: M2 size: 2 GiB speed: 667 MT/s type: DDR2

So, like for the original post, also on my system, only 3 GB out of the 
present 4 GB can be used. This problem seems to be a Debian (Linux in 
general?) problem, because MS Win makes full use of the 4 GB RAM as 
physically present.

Re: why 1G memory is missing?

[Andy Smith]

Hello,

On Tue, Aug 03, 2021 at 07:14:32AM +0800, loushanguan2...@sina.com wrote:
> Linux debian 4.9.0-13-686-pae #1 SMP Debian 4.9.228-1 (2020-07-05) i686 
> GNU/Linux

So you are running 32-bit kernel. Will the hardware do 64-bit? What
does

$ cat /proc/cpuinfo

say?

You may be able to install an amd64 kernel and see all memory even
though userland is still 32-bit.

Thanks,
Andy

Re: why 1G memory is missing?

[Jeremy Hendricks]

It’s bios/chipset dependent. Example: the Intel 945 will not allow more
than 3.25GB or so regardless if PAE is used. However, the Intel 965 chipset
will provide the full 4GB if used with PAE enabled and the BIOS allows it
by default or has a ‘remap’ option.

On Mon, Aug 2, 2021 at 7:15 PM  wrote:

> Jeremy Hendricks:
> Are you booting an x86 or x86_64 install? Run: “uname -a” without quotes
> and post the results to us.
>
>
> Linux debian 4.9.0-13-686-pae #1 SMP Debian 4.9.228-1 (2020-07-05) i686
> GNU/Linux
>
> Thanks, i thought pae can bypass 4G limit of 32-bit OS
>
>

Re: why 1G memory is missing?

[loushanguan2015]

Jeremy Hendricks:Are you booting an x86 or x86_64 install? Run: “uname -a” 
without quotes and post the results to us.

Linux debian 4.9.0-13-686-pae #1 SMP Debian 4.9.228-1 (2020-07-05) i686 
GNU/Linux
Thanks, i thought pae can bypass 4G limit of 32-bit OS

Re: why 1G memory is missing?

[IL Ka]

> i have 2 memory slots
> memtest86+ shows each has 2G, but total is 3G
> after booting linux, top shows total is 3G
>
why 1 G is missing? Thanks!
>


You probably have 32bit OS
https://en.wikipedia.org/wiki/3_GB_barrier

Re: why 1G memory is missing?

[Jeremy Hendricks]

Are you booting an x86 or x86_64 install? Run: “uname -a” without quotes
and post the results to us.

On Mon, Aug 2, 2021 at 6:12 PM  wrote:

> i have 2 memory slots
> memtest86+ shows each has 2G, but total is 3G
> after booting linux, top shows total is 3G
> why 1 G is missing? Thanks!
>

why 1G memory is missing?

[loushanguan2015]

i have 2 memory slotsmemtest86+ shows each has 2G, but total is 3Gafter booting 
linux, top shows total is 3Gwhy 1 G is missing? Thanks!