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Date:      Thu, 11 Jan 2018 10:08:49 -0500
From:      Aryeh Friedman <aryeh.friedman@gmail.com>
To:        galtsev@kicp.uchicago.edu
Cc:        Lowell Gilbert <freebsd-questions-local@be-well.ilk.org>,  FreeBSD Mailing List <freebsd-questions@freebsd.org>
Subject:   Re: OT: Max system physical memory
Message-ID:  <CAGBxaXkGNoOzsTqUF3n5HipweBg4NUib__OKCXuPPZmq7-OAJA@mail.gmail.com>
In-Reply-To: <50615.108.68.170.208.1515682927.squirrel@cosmo.uchicago.edu>
References:  <CAGBxaX=+YUuDBOp5n1Kjq6xaJmjEpZ8kWARNMnE_3LwBkNM6GA@mail.gmail.com> <44wp0ofr1w.fsf@be-well.ilk.org> <50615.108.68.170.208.1515682927.squirrel@cosmo.uchicago.edu>

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On Thu, Jan 11, 2018 at 10:02 AM, Valeri Galtsev <galtsev@kicp.uchicago.edu>
wrote:

>
> On Thu, January 11, 2018 7:44 am, Lowell Gilbert wrote:
> > Aryeh Friedman <aryeh.friedman@gmail.com> writes:
> >
> >> My computer (HP Pavilion P7-1234, FreeBSD 11.1-RELEASE [amd64]) has 2
> >> 240
> >> pin DIMM (DDR3, PC3-10600) the manual says the max memory is 8 GB but I
> >> see
> >> some 16 GB packages (2x8GB).   If I put one or two of these in will it
> >> see
> >> the extra memory?
> >
> > Probably not.
> >
>
> It is hit and miss. It is possible that specifications were written based
> on largest available modules at the moment of writing. If replacement
> modules are compatible with memory controller (i.e., say, the same
> PC3-10600), it is possible they will work. There still is the chance they
> will not work reliably, _IF_ there are some less trivial specs of memory
> controller are involved. Such may be: bus amplifiers may only handle up to
> this capacitive load before signals go out of specs. In general, larger
> RAM has larger numbers of address inputs connected to given lead, which
> may entail larger capacitive load. System board layout may have its impact
> here as well. Apart from that (and maybe some internal schematic specifics
> of memory controller), there is nothing fundamental about 8 GB RAM limit,
> so it may work. But chance is it will not.
>
>
sysutils/dmidecode disagrees with the manual thus deeping my confusion (I
bought the memory and use it in an other machine that does support upto
32GB and only has 8 spread across 2 VM's):

oot@lilith:~ # dmidecode -t memory
# dmidecode 3.1
Scanning /dev/mem for entry point.
SMBIOS 2.7 present.

Handle 0x000A, DMI type 16, 23 bytes
Physical Memory Array
    Location: System Board Or Motherboard
    Use: System Memory
    Error Correction Type: None
    Maximum Capacity: 128 GB
    Error Information Handle: Not Provided
    Number Of Devices: 2

Handle 0x000C, DMI type 17, 34 bytes
Memory Device
    Array Handle: 0x000A
    Error Information Handle: Not Provided
    Total Width: 64 bits
    Data Width: 64 bits
    Size: 4096 MB
    Form Factor: DIMM
    Set: None
    Locator: A1_DIMM0
    Bank Locator: A1_BANK0
    Type: DDR3
    Type Detail: Synchronous
    Speed: 1333 MT/s
    Manufacturer: Samsung
    Serial Number: 938D8E07
    Asset Tag: A1_AssetTagNum0
    Part Number: M378B5273CH0-CH9
    Rank: 2
    Configured Clock Speed: 667 MT/s

Handle 0x000E, DMI type 17, 34 bytes
Memory Device
    Array Handle: 0x000A
    Error Information Handle: Not Provided
    Total Width: 64 bits
    Data Width: 64 bits
    Size: 4096 MB
    Form Factor: DIMM
    Set: None
    Locator: A1_DIMM1
    Bank Locator: A1_BANK1
    Type: DDR3
    Type Detail: Synchronous
    Speed: 1333 MT/s
    Manufacturer: Samsung
    Serial Number: 938D8C71
    Asset Tag: A1_AssetTagNum1
    Part Number: M378B5273CH0-CH9
    Rank: 2
    Configured Clock Speed: 667 MT/s



-- 
Aryeh M. Friedman, Lead Developer, http://www.PetiteCloud.org



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