[Dmidecode For Mac
Oludare Padilla
The DMI table decoder is a command-line tool for Linux systems. It is commonly used to translate a machine's DMI table (System Management BIOS, or SMBIOS) into a human-readable format. This tool allows you to see additional information about a system's hardware configuration, and even gives information not directly related to the current build. Information like the maximum supported amount of memory or the fastest-supported CPU type can be found by using a few key flags.
From a practical standpoint, you might run into situations where you need a serial number or a key piece of hardware information during troubleshooting. In my time as a storage engineer, I ran into multiple instances where a customer would purchase a virtual edition server and then try to run massive amounts of data backups or replication to this machine. Depending on the size of the jobs, they would sometimes overload the memory included and exceed the swap space. In turn, this issue would cause Out-of-Memory (OOM) Killer to have a field day with the system. So, rather than looking up hardware specs in a manual, I could use dmidecode to grab this information.
First off, all of the following information can be found in the man-pages for the tool by running man dmidecode. Feel free to follow along there. At the most basic level, each record has one of the following (as listed in the man page):
Size - Each record has a 4-byte header (2 for the handle, 1 for the type, 1 for the size), the rest is used by the record data. This vaule does not take the text strings into account (these are placed at the end of the record), so the actual length of a record may be (and is often) greater than the displayed value
There are many options that can be used to create a more precise output. I will not cover all of these here, but they are laid out plainly using the man page. What I will talk about are the DMI type codes that are included with the command to make specific information rapidly accessible. Going back to my previous example, you will remember that we routinely had issues with OOM errors. To gather information about a system's memory configuration, you can use the following command:
where x is equal to the numeric type code you wish to gather. For this example, the codes 5, 6, 16, and 17 would all be helpful to gather. See the man page's full chart below for all the available type codes:
Keywords can be used with the --type flag to pull all associated type codes into the command. From the example below, you can see that all of the information associated with using numerical type codes 16 and 17 is supplied:
I hope that this quick rundown of the DMI Decoder tool has been helpful. Let us know when you have used this command or had need of it. Hopefully, you now have a better strategy or reference point for the next hardware issue you run into.
Tyler is the Sr. Community Manager at Enable Sysadmin, a submarine veteran, and an all-round tech enthusiast! He was first introduced to Red Hat in 2012 by way of a Red Hat Enterprise Linux-based combat system inside the USS Georgia Missile Control Center. More about me
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Dmidecode reports information about your system's hardware as described in yoursystem BIOS according to theSMBIOS/DMIstandard (see a sample output). This informationtypically includes system manufacturer, model name, serial number, BIOS version, assettag as well as a lot of other details of varying level of interest and reliabilitydepending on the manufacturer. This will often include usage status for the CPUsockets, expansion slots (e.g. AGP, PCI, ISA) and memory module slots, and the list of I/Oports (e.g. serial, parallel, USB).
DMI data can be used to enable or disable specific portions ofkernel code depending on the specific hardware.Thus, one use of dmidecode is for kernel developers to detect system "signatures" and add them to thekernel source code when needed.
Dmidecode was first written by Alan Cox, then was further developed and iscurrently maintained again by Jean Delvare, after a 5-year interim by Anton Arapov.It is released under the General Public License (GPL). For more details, you should have a look at theAUTHORSandLICENSEfiles that come with the source code.
No binaries are available here, but dmidecode is packagedfor several Linux and BSD distributions (Debian,Gentoo,openSUSE andFreeBSDamong others), either as an individual package or included in a more generic tool set.BeOS andDOS packagesare also known to exist.
dmidecode is a free userspace command-line utility for Linux that can parse the SMBIOS data.[1][2] The name dmidecode is derived from Desktop Management Interface, a related standard with which dmidecode originally interfaced. SMBIOS was originally named DMIBIOS. The Linux kernel and other modern operating systems such as the BSD family contain an SMBIOS decoder, allowing systems administrators to inspect system hardware configuration and to enable or disable certain workarounds for problems with specific systems, based on the provided SMBIOS information. Information provided by this utility typically includes the system manufacturer, model name, serial number, BIOS version and asset tag, as well other details of varying level of interest and reliability, depending on the system manufacturer. The information often includes usage status for the CPU sockets, expansion slots (including AGP, PCI and ISA) and memory module slots, and the list of I/O ports (including serial, parallel and USB).[3][4] Decoded DMI tables for various computer models are collected in a public GitHub repository.[5]
Aniruddh yes the H300's only support 32gb ram max (officially) its notthe cpu support in this case its the mobo limited/locked support allbios are locked so unless its a modded bios (which i strongly dontrecommend doing neither its allowed to discuss anything about it inthis community ) probably it wont support so until someone buys 32gbsodimms and test them theres no way to know if its will support or notand i doubt anyone would take such a risk on a such high priced ramwithout having sure if it would really work or not but anyway of youare willing to go for it also why would u need 64gb 32 its already toomuch no one will ever use them in full and its not having 64gb thatwould make the laptop faster in some rare cases too much unused ramcould also cause some bottleneck and decrease the performance but goodluck :)
i believe my server is quad channel ram and with 4 cpus the reason for all of everything shown above. However note the "max capacity" of 384gb reported, how/where that it listed which I did not indicate above each is for a Physical Memory Array. It gets complicated and you have to dive into the memory channel specifics to get an accurate understanding... but my server does not have a max capacity of 384gb ram nor does it have a max capacity of 3072 gb. I believe based the true max ram available to the operating system is based on cpu/memory architecture; for me is 768gb and I think under certain circumstances (for other servers) can be 1.5tb if using certain low voltage DIMMS and the [server] BIOS supports it. Note however the that does not correspond to the reported number of 384, which are all listed under Physical Memory Array in my case. So it is a matter of interpretation, or misinterpretation rather. This Maximum Capacity does not refer to the maximum amount of usable RAM seen by the operating system, it is reporting a low level memory channel interface. So while i don't doubt dmidecode is not 100% reliable regarding every bit of hardware it is interfacing, you have to really dive in and understanding what values it is trying to report on.
Your laptop being 1 cpu and I suppose 2 memory channels vs a 4 socket server like I listed above... obvious differences aside based on what you said for your specific laptop I suspect you are seeing a max capacity of 64gb at the hardware manufacturer memory channel level but in the end that Asus laptop it will be that Asus bios code being what's really in charge. If Asus says only supports 32gb I would believe that because it's that bios code making that happen not the hardware memory channel capability of 64gb being reported by dmidecode. It would be getting down to computer engineering level- i suspect ASUS (and everyone else) use all the same memory channel type hardware which is capable of referencing a 64gb DIMM but there's other hardware in play which makes a 32gb limit actually happen. I wouldn't necessarily go thinking ASUS simply programmed BIOS code to simply limit the laptop to 32gb when it really could have 64gb.
You also mentioned H300, which is an intel chipset... recognize any consumer pc motherboard like that has only 2 DIMM slots vs 4 DIMM slots of a higher end Z370 chipset for example... all those 2 DIMM motherboards are all limited to 32gb total RAM vs 64gb total ram of the 4 DIMM motherboards. So I would not try to put 64gb of ram in your laptop it's not going to work. I can also tell you fwiw I've tried installing Windows 7 pro on my 512gb server and only 192gb shows up as usable in Windows.
why would u need 64gb 32 its already too much no one will ever use them in full and its not having 64gb that would make the laptop faster in some rare cases too much unused ram could also cause some bottleneck and decrease the performance but good luck :)
unused ram does not cause bottleneck or decrease performance. That answer is out of context and neglects a lot of low level architecture and memory channel layout which is the reason why/how ram quantities can affect performance [at the hardware level]. And luck has nothing to do with it.
The real question is not dmidecode itself being trustworthy but whether the information it reads is actually reliable or not. As quoted in your question, dmidecode does not effectively scan your hardware, but instead reads some data stored in the BIOS for any kind of management software (Desktop Management Interface, DMI spec. on the DMTF site).
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