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My HP N40L "MicroServer" only supports up to 8GB RAM, but I have it running now with 16GB. Sometimes FreeNAS will boot saying there is 16GB, and other times it

My HP N40L "MicroServer" only supports up to 8GB RAM, but I have it running now with 16GB. Sometimes FreeNAS will boot saying there is 16GB, and other times it will boot saying there is only 8GB. I'm unwilling to risk loosing that old reliable system via a potentially dangerous BIOS hack, but it sure would be nice not have to reboot it until I win the lucky 16GB jackpot.

orev 8y ago
I would be concerned that there’s some electrical reason why it’s detected intermittently, and that the extra 8GB could easily disappear while the system is running.
- segfaultbuserr 8y ago
  Low-level software is responsible for most memory issues, but there are definitely electrical reasons, too. For example, I have a devboard that only support 1 GiB of DDR2 RAM, but it's a 64-bit system and the memory controller on the CPU was supposed to support at least 2 GiB of RAM. Meanwhile, another board that uses the identical chip runs 2 GiB RAM without problems. The engineers of the devboard briefly explained that the problem was electrical. The memory controller itself has inadequate drive strength, adding more RAMs would increase the load on the DDR bus and destabilize the system. On the other hand, the other board had better PCB layout so the problem did not occur.
  - equalunique 8y ago
    I would sure like to find an inexpensive Mini-ITX motherboard in 2019 that could run my 2x8GB sticks of 204-pin DDR3 ECC UDIMMs properly.
    - remlov 8y ago
      Holy smokes. I thought finding an ITX board for 2x8GB sticks of full size 240-pin DDR3 ECC UDIMMs was hard.
      - segfaultbuserr 8y ago
        I have a Mini-ITX board, I noticed that if I activate XMP, the board will cease to work, but it works with 4 GiB of RAM at standard frequency. So it seems memory is a general problem among Mini-ITX boards? Perhaps the reason is that these boards have less available space for routing, fewer layers, and targets a lower price, so they trend to have worse electrical characteristics?
        remlov 8y ago
        Quality of the PCB and the number of layers definitely plays a factor I'm sure it isn't limited to ITX though. I have noticed compatible differences between super robust Intel ITX boards vs ECS thin and wobbly ITX boards, with the ECS board having more issues, quirks and what not.
  - spockz 8y ago
    I had something similar with my 2011 MBP. I had it running just fine with 16GB of ram even though it officially only supported 8GB. After having the main board replaced because of a defective graphics card I could not run it with more than 8GB without it crashing continuously.
    - bluedino 8y ago
      Should work fine. I wonder if you needed a firmware update?
- mikeash 8y ago
  I once had a defective 512MB RAM module. Usually it would be detected as a 256MB module and it would work fine. Sometimes it would be detected as a 512MB module, but corrupted data would crash the system within a few minutes.
  - jacob019 8y ago
    You used to be able to scan memory consistency and pass a kernel parameter to skip bad regions of memory. I ran a system for years with known bad memory that way.
- userbinator 8y ago
  ...and it probably already has, multiple times, but you haven't noticed because you've not used that much RAM. The BIOS does a (relatively) quick memory check in the POST to detect how much memory is actually available, basically by writing a series of patterns to all addresses and then reading them back to confirm; some desktops have a "fast boot" option which mostly skips it (I believe it's something like testing one byte per 4KB instead of every byte), and servers usually have a much more thorough test that can take many minutes. The best way to check whether the memory is functional when 16GB is detected is to run a memory tester like MemTest86.
fyfy18 8y ago
Same here on a N54L. Officially these machines only accept 8GB, but plenty of people say they run fine with 16GB.
kalleboo 8y ago
I've done the same thing with a Synology NAS. Both Synology and the Intel CPU datasheet say it only supports 8 GB of RAM, but put 16 GB in it and it will use it. The Synology web UI only shows 8 GB and it breaks the graph display in the memory usage monitor (although when I first installed it, it used to show 16 GB but after some update, or random reboot, it stopped. Haven't tried rebooting to see if it's just random)
kstenerud 8y ago
Are you sure about that? I bought mine with 16gb a number of years ago and still use it as a NAS + plex server (zfs loves to chew through ram). The wikia page also talks about it: https://n40l.fandom.com/wiki/Memory https://n40l.fandom.com/wiki/Memory
- Spare_account 8y ago
  The "supports 16Gb" assertion on the page you've linked to is sourced from another forum page: https://hardforum.com/threads/hp-proliant-microserver-owners-thread.1555868/page-17#post-1038749416 https://hardforum.com/threads/hp-proliant-microserver-owners... > It seems to be confirmed, that these wonderfull little boxen can actually support 16Gb Memory, not the 8Gb HP Says they are limited to. So it would appear that HP doesn't officially support 16Gb, which puts us firmly back in the territory of this post, YMMV, etc.
gyrgtyn 8y ago
I got two from the same guy on craiglist and they already had 16GB and it works everytime. Not sure what he did but I'm glad I wasn't the one fiddling with the BIOS
ownagefool 8y ago
I ran the hacked bios and it worked, for what that's worth. This was when they were fairly new.
TMWNN 7y ago
As kstenerud said, https://n40l.fandom.com/wiki/Memory https://n40l.fandom.com/wiki/Memory discusses this issue. More accurately, the comments discuss it, with some reporting your issue. I am among those who've never had problems with detecting 16GB; I use two KVR1333D3E9S/8G.

orev 8y ago

I would be concerned that there’s some electrical reason why it’s detected intermittently, and that the extra 8GB could easily disappear while the system is running.

segfaultbuserr 8y ago
Low-level software is responsible for most memory issues, but there are definitely electrical reasons, too. For example, I have a devboard that only support 1 GiB of DDR2 RAM, but it's a 64-bit system and the memory controller on the CPU was supposed to support at least 2 GiB of RAM. Meanwhile, another board that uses the identical chip runs 2 GiB RAM without problems. The engineers of the devboard briefly explained that the problem was electrical. The memory controller itself has inadequate drive strength, adding more RAMs would increase the load on the DDR bus and destabilize the system. On the other hand, the other board had better PCB layout so the problem did not occur.
- equalunique 8y ago
  I would sure like to find an inexpensive Mini-ITX motherboard in 2019 that could run my 2x8GB sticks of 204-pin DDR3 ECC UDIMMs properly.
  - remlov 8y ago
    Holy smokes. I thought finding an ITX board for 2x8GB sticks of full size 240-pin DDR3 ECC UDIMMs was hard.
    - segfaultbuserr 8y ago
      I have a Mini-ITX board, I noticed that if I activate XMP, the board will cease to work, but it works with 4 GiB of RAM at standard frequency. So it seems memory is a general problem among Mini-ITX boards? Perhaps the reason is that these boards have less available space for routing, fewer layers, and targets a lower price, so they trend to have worse electrical characteristics?
      - remlov 8y ago
        Quality of the PCB and the number of layers definitely plays a factor I'm sure it isn't limited to ITX though. I have noticed compatible differences between super robust Intel ITX boards vs ECS thin and wobbly ITX boards, with the ECS board having more issues, quirks and what not.
- spockz 8y ago
  I had something similar with my 2011 MBP. I had it running just fine with 16GB of ram even though it officially only supported 8GB. After having the main board replaced because of a defective graphics card I could not run it with more than 8GB without it crashing continuously.
  - bluedino 8y ago
    Should work fine. I wonder if you needed a firmware update?
mikeash 8y ago
I once had a defective 512MB RAM module. Usually it would be detected as a 256MB module and it would work fine. Sometimes it would be detected as a 512MB module, but corrupted data would crash the system within a few minutes.
- jacob019 8y ago
  You used to be able to scan memory consistency and pass a kernel parameter to skip bad regions of memory. I ran a system for years with known bad memory that way.
userbinator 8y ago
...and it probably already has, multiple times, but you haven't noticed because you've not used that much RAM. The BIOS does a (relatively) quick memory check in the POST to detect how much memory is actually available, basically by writing a series of patterns to all addresses and then reading them back to confirm; some desktops have a "fast boot" option which mostly skips it (I believe it's something like testing one byte per 4KB instead of every byte), and servers usually have a much more thorough test that can take many minutes. The best way to check whether the memory is functional when 16GB is detected is to run a memory tester like MemTest86.

fyfy18 8y ago

Same here on a N54L. Officially these machines only accept 8GB, but plenty of people say they run fine with 16GB.

kalleboo 8y ago

I've done the same thing with a Synology NAS. Both Synology and the Intel CPU datasheet say it only supports 8 GB of RAM, but put 16 GB in it and it will use it. The Synology web UI only shows 8 GB and it breaks the graph display in the memory usage monitor (although when I first installed it, it used to show 16 GB but after some update, or random reboot, it stopped. Haven't tried rebooting to see if it's just random)

kstenerud 8y ago

Are you sure about that? I bought mine with 16gb a number of years ago and still use it as a NAS + plex server (zfs loves to chew through ram). The wikia page also talks about it: https://n40l.fandom.com/wiki/Memory https://n40l.fandom.com/wiki/Memory

Spare_account 8y ago
The "supports 16Gb" assertion on the page you've linked to is sourced from another forum page: https://hardforum.com/threads/hp-proliant-microserver-owners-thread.1555868/page-17#post-1038749416 https://hardforum.com/threads/hp-proliant-microserver-owners... > It seems to be confirmed, that these wonderfull little boxen can actually support 16Gb Memory, not the 8Gb HP Says they are limited to. So it would appear that HP doesn't officially support 16Gb, which puts us firmly back in the territory of this post, YMMV, etc.

gyrgtyn 8y ago

I got two from the same guy on craiglist and they already had 16GB and it works everytime. Not sure what he did but I'm glad I wasn't the one fiddling with the BIOS

ownagefool 8y ago

I ran the hacked bios and it worked, for what that's worth. This was when they were fairly new.

TMWNN 7y ago

As kstenerud said, https://n40l.fandom.com/wiki/Memory https://n40l.fandom.com/wiki/Memory discusses this issue. More accurately, the comments discuss it, with some reporting your issue. I am among those who've never had problems with detecting 16GB; I use two KVR1333D3E9S/8G.