Hello,

I do have a problem getting my RAM recognized. I have a A75M-HVS motherboard, equipped with:

+ 2*2GiB memory (BLT2G3D1869DT1TX0): Crucial Ballistix 240-pin DIMM
DDR3 PC3-14900 • 9-9-9-24 • Unbuffered • NON-ECC
DDR3-1866 • 1.5V • 256Meg x 64

+ AMD A6-3670 APU with Radeon(tm) HD Graphics: This is important as this takes 512MB (at least what BIOS says)

Crucial says the RAM is compatible with MB, ASRock only list other RAMs.
When booting, just after the BIOS and before GRUB, I do see a (what I think i a BIOS) screen where it is written: 3584 MB RAM. I'm happy about that ;-)

Once logged, top, free or other tools report a total of 1477 MiB :-(
Actually, also running memtest chosen in the GRUB menu list 1477 MiB

Finally, what I found the most interesting, is the output of lshw -c memory under my ubuntu 12.04 (Linux muc.guigui 3.2.0-31-generic #50-Ubuntu SMP Fri Sep 7 16:16:45 UTC 2012 x86_64 x86_64 x86_64 GNU/Linux):

- as a "normal" user:
WARNING: you should run this program as super-user.
*-memory
description: System memory
physical id: 0
size: 1477MiB
WARNING: output may be incomplete or inaccurate, you should run this program as super-user.

- as a superuser:
...
...
*-memory
description: System Memory
physical id: 8
slot: System board or motherboard
size: 4GiB
*-bank:0
description: DIMM DDR3 Synchronous 1333 MHz (0,8 ns)
product: BLT2G3D1869DT1TX0.
vendor: Undefined
physical id: 0
serial: A80282C1
slot: A1_DIMM0
size: 2GiB
width: 64 bits
clock: 1333MHz (0.8ns)
...
...

Looking at the the output of dmesg, I also only see the little memory:
...
...
[ 0.000000] BIOS-provided physical RAM map:
[ 0.000000] BIOS-e820: 0000000000000000 - 000000000009ec00 (usable)
[ 0.000000] BIOS-e820: 000000000009ec00 - 00000000000a0000 (reserved)
[ 0.000000] BIOS-e820: 00000000000e0000 - 0000000000100000 (reserved)
[ 0.000000] BIOS-e820: 0000000000100000 - 000000005e77c000 (usable)
[ 0.000000] BIOS-e820: 000000005e77c000 - 000000005e7c5000 (ACPI NVS)
[ 0.000000] BIOS-e820: 000000005e7c5000 - 000000005e7ce000 (ACPI data)
[ 0.000000] BIOS-e820: 000000005e7ce000 - 000000005e7d2000 (reserved)
[ 0.000000] BIOS-e820: 000000005e7d2000 - 000000005e7d5000 (ACPI NVS)
[ 0.000000] BIOS-e820: 000000005e7d5000 - 000000005e7d6000 (usable)
[ 0.000000] BIOS-e820: 000000005e7d6000 - 000000005ea32000 (reserved)
[ 0.000000] BIOS-e820: 000000005ea32000 - 000000005ea33000 (ACPI NVS)
[ 0.000000] BIOS-e820: 000000005ea33000 - 000000005ea44000 (reserved)
[ 0.000000] BIOS-e820: 000000005ea44000 - 000000005ea4b000 (ACPI NVS)
[ 0.000000] BIOS-e820: 000000005ea4b000 - 000000005ea73000 (reserved)
[ 0.000000] BIOS-e820: 000000005ea73000 - 000000005ec76000 (ACPI NVS)
[ 0.000000] BIOS-e820: 000000005ec76000 - 000000005ef00000 (usable)
[ 0.000000] BIOS-e820: 00000000e0000000 - 00000000f0000000 (reserved)
[ 0.000000] BIOS-e820: 00000000fec00000 - 00000000fec01000 (reserved)
[ 0.000000] BIOS-e820: 00000000fec10000 - 00000000fec11000 (reserved)
[ 0.000000] BIOS-e820: 00000000fed00000 - 00000000fed01000 (reserved)
[ 0.000000] BIOS-e820: 00000000fed61000 - 00000000fed71000 (reserved)
[ 0.000000] BIOS-e820: 00000000fed80000 - 00000000fed90000 (reserved)
[ 0.000000] BIOS-e820: 00000000ff000000 - 0000000100000000 (reserved)
...
...
[ 0.000000] original variable MTRRs
[ 0.000000] reg 0, base: 0GB, range: 2GB, type WB
[ 0.000000] reg 1, base: 1519MB, range: 1MB, type UC
[ 0.000000] reg 2, base: 1520MB, range: 16MB, type UC
[ 0.000000] reg 3, base: 1536MB, range: 512MB, type UC
[ 0.000000] total RAM covered: 1519M
[ 0.000000] Found optimal setting for mtrr clean up
[ 0.000000] gran_size: 64K chunk_size: 32M num_reg: 4 lose cover RAM: 0G
[ 0.000000] New variable MTRRs
[ 0.000000] reg 0, base: 0GB, range: 1GB, type WB
[ 0.000000] reg 1, base: 1GB, range: 512MB, type WB
[ 0.000000] reg 2, base: 1519MB, range: 1MB, type UC
[ 0.000000] reg 3, base: 1520MB, range: 16MB, type UC
[ 0.000000] found SMP MP-table at [ffff8800000fcee0] fcee0
[ 0.000000] initial memory mapped : 0 - 20000000
[ 0.000000] Base memory trampoline at [ffff880000099000] 99000 size 20480
[ 0.000000] Using GB pages for direct mapping
[ 0.000000] init_memory_mapping: 0000000000000000-000000005ef00000
[ 0.000000] 0000000000 - 0040000000 page 1G
[ 0.000000] 0040000000 - 005ee00000 page 2M
[ 0.000000] 005ee00000 - 005ef00000 page 4k
[ 0.000000] kernel direct mapping tables up to 5ef00000 @ 1fffd000-20000000
...
...

I do not know what to do next. Maybe I'll try to boot other systems to see what is then happening. If you have any idea on how to fix that, thanks for sharing !

"Actually, also running memtest chosen in the GRUB menu list 1477 MiB"

Memtest is basically a different OS so you have some issue with your memory or controller or possibly some bios setting that is taking that memory (unlikely).

Does bios show correct? Boot to bios and see.

Can you post the output of 'cat /proc/meminfo'

Thanks for these replies... I stopped doing something with SW and went to HW (as jefro mentionned)
I exchanged both RAM modules and I now have my 3.5 GiB. May be they were wrongly inserted or so.
In anycase, I feel better. I guess the output from the superuser lshw was actually being taken from the memory somehow and not from the mainboard (so represented the declared value and not the available one).
Now I have full memory, only problem is I do not get it running at max speed. But I'll google around and eventually will fix it

Thanks again

Correct.

There is a ram controller that the BIOS has configured. In most AMD designs, that controller is physically inside the CPU chip. In other designs, that controller is inside some other major chip on the motherboard. But regardless of location, it is something the BIOS needs to configure during power up.

The ram you can use (and the ram reported in that E820 table) is only ram that the BIOS has configured the ram controller to access.

lshw and various other tools have a different path to the ram to get the info about how the ram manufacturer suggests the BIOS configure it. The BIOS uses that same path to get the ram info before it configures the ram controller.

For various reasons, the BIOS may decide not to configure the ram controller for all of the ram. If it finds some problem with part of the ram (such as the results of a dirty contact) you would expect it to display a warning message before skipping that ram when configuring the ram controller. But I have never seen that happen. Instead the BIOS silently skips some of the ram. Even more confusing, when it reports ram size the BIOS reports the whole amount it saw via that pre configuration alternate path. It does not report the lower amount it actually configured.

Keep playing with the ram and settings in bios but always test them in memtest fully for a day or so. On the opening screen for memtest you will see how memtest see's the ram so be sure to read it all and set any settings to correct how it is tested.

In some cases, memtest failing is not a bad thing.

Thanks again. I actually played with it and saw that the BIOS was using what he found "optimal". Higher frequency were not working because of the other settings (CAS, ...). It was using 7 7 7 21 @ DDR3-1066. I found that it is better in my case to have 9 9 9 24 @ DDR3-1866
I can even now overclock a little, all looks stable.
Very good help here. I came with a half under-clock memory 2 days ago. I now have a fulld working over-clocked memory and learned something about how the info are being passed memory->BIOS ;-)

Unless your memory is rated at less than DDR3-1866 running at 1866 isnt overclocking at all, as the A6-3670 is designed to use up to DDR3-1866 (apart from a few oddball models, all the A series is rated for DDR3-1866).

http://www.amd.com/us/products/deskt...omparison.aspx

Yes, I actually bought the memory to fit with the AMD APU. So, DDR3-1866 as you mentioned. As said, my MoBo liked to have it running at DDR3-1066 and I changed the parameters to get 1866. I was so excited, that I even turned on the "overclock" parameter from 100 to 104. So, I'm actually at DDR3-1940.
So sorry, I wrote slower that I thought, I actually got the memory working at right speed and then overclocked the whole thing.

I have Memtested performances of 3.8 GB/s (I used the whole time memtest average R/W speed as my memory "benchmark"). Also looked at the diff under ubuntu system profiler (hardinfo) and it makes some difference (the memory speed/params, the overclock has a little effect - relative to the 4% as it should I guess be)

This APU is working actually quite good. I guess that for the 70€ price, one of the best price/performances ratio, also to be seen in Passmark ! Also the glmark2 gives a 1k score for the Radeon which is quite good !

All in all, I'm happy

Keep in mind that on CPUs with inbuilt memory controller you always overclock the memory controller also, when you overclock the RAM over the limits of the memory controller, so keep an eye on the CPU temperatures.