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Catzi67
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Prodesk 405 G4 - Memory Speed

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Prodesk 405 G4
Microsoft Windows 10 (64-bit)

The 405 G4's memory should run at 2400Mhz. I have 4 dimms of 16GB ram which is the maximum this unit can take.

 

If I install 16GB or 32GB of RAM (any of the four dimms) the memory runs at 2400MHz

 

If I insert all four of the dimms, the memory speed drops to 1866MHz

 

When I look at the HP Device Diagnostics it reports that all four dimms are 2400Mhz capable.

 

All four dimms are identical and are as specified in the 405 G4 manual. I think this may be a BIOS issue. The manual does not mention that memory operation is slower when fully populated.

 

I have tried chatting to a support rep online but go round in circles. Anyone got any thoughts as to how I can get this resolved?

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DGroves
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there is nothing to resolve, the hp specs for this system show that they only officially support 2 sodimms in 16/32 GB configurations at 2666 and hp notes:

 

NOTE: 

Actual data rate is determined by both the system configured processor and memory module(s) installed.
 
your post says 4 sodimm slots so i have to question if you have the model number of the system correctly posted?
 
many systems will drop the speeds of ram if installing 4 memory modules due to loading of the memory bus
 
 
 
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Catzi67
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Sorry - you're quoting memory for the mini PC. I have the small form-factor unit. To quote the manual:

 

The memory sockets on the system board are populated with at least one preinstalled memory module. To achieve the maximum memory support, you can populate the system board with up to 64 GB of memory configured in a high-performing dual-channel mode.

 

Nowhere does it mention bus speed is reduced if the memory is fully populated. 

 

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DGroves
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for the "SFF" model the maintenance and service guide states:

(note the CAS LATENCY  numbers 17-17-17) do your modules run at this speed? if not that's why it runs slower

 

https://h30434.www3.hp.com/t5/forums/replypage/board-id/Business-PC-Workstation-POS/message-id/38078

 

https://www.crucial.com/compatible-upgrade-for/hp---compaq/hp-prodesk-405-g4-small-form-factor

 

Memory
The computer comes with double data rate 4 synchronous dynamic random access memory (DDR4-SDRAM) dual
inline memory modules (DIMMs).
The memory sockets on the system board are populated with at least one preinstalled memory module. To
achieve the maximum memory support, you can populate the system board with up to 64 GB of memory
conƭgured in a high-performing dual-channel mode.
For proper system operation, the DIMMs must adhere to the following speciƭcations:
● Industry-standard 288-pin
● 8nbuƫered non-ECC PC4-19200 DDR4-2400 MHz-compliant
● 1.2 volt DDR4-SDRAM memory modules
● CAS latency 17 DDR4 2400 MHz (17-17-17 timing)
● Mandatory JEDEC SPD information
The computer supports the following:
● 512 Mb, 1 Gb, 2 Gb, and 4 Gb non-ECC memory technologies
● Single-sided and double-sided memory modules
● Memory modules constructed with x8 and x16 DDR devices; memory modules constructed with x4 SDRAM
are not supported
NOTE: The system does not operate properly if you install unsupported memory modules.
Populating DIMM sockets
There are four memory sockets on the system board, with two sockets per channel. The sockets are labeled
DIMM1, DIMM2, DIMM3, and DIMM4. Sockets DIMM1 and DIMM3 operate in memory channel B. Sockets DIMM2
and DIMM4 operate in memory channel A.
The system will automatically operate in single-channel mode, dual-channel mode, or flex mode, depending on
how the DIMMs are installed.
NOTE: Single-channel and unbalanced dual-channel memory conƭgurations will result in inferior graphics
performance.
● The system will operate in single-channel mode if the DIMM sockets are populated in one channel only.
● The system will operate in a higher-performing dual-channel mode if the total memory capacity of
the DIMMs in Channel A is equal to the total memory capacity of the DIMMs in Channel B. The technology
and device width can vary between the channels. For example, if Channel A is populated with two 1 GB
DIMMs and Channel B is populated with one 2 GB DIMM, the system will operate in dual-channel mode.
● The system will operate in flex mode if the total memory capacity of the DIMMs in Channel A is not equal to
the total memory capacity of the DIMMs in Channel B. In flex mode, the channel populated with the least
amount of memory describes the total amount of memory assigned to dual channel and the remainder is
assigned to single channel. For optimal speed, the channels should be balanced so that the largest amount
of memory is spread between the two channels. If one channel will have more memory than the other,
the larger amount should be assigned to Channel A. For example, if you are populating the sockets with
one 2 GB DIMM, and three 1 GB DIMMs, Channel A should be populated with the 2 GB DIMM and one 1 GB
24 Chapter 4 Removal and replacement procedures
DIMM, and Channel B should be populated with the other two 1 GB DIMMs. With this conƭguration, 4 GB will
run as dual-channel and 1 GB will run as single-channel.
● In any mode, the maximum operational speed is determined by the slowest DIMM in the system

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Catzi67
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The memory I have installed meets the specification outlined in the manual exactly.

 

https://www.crucial.com/memory/ddr4/ct16g4dfd824a

 

DDR4 PC4-19200 • CL=17 • Dual Ranked • x8 based • Unbuffered • NON-ECC • DDR4-2400 • 1.2V 

 

As mentioned previously, the memory performs at 2400Mhz when installed as a single 16GB module or 32GB (two modules).

 

When I populate 64GB (four dimms), memory performance drops to 1866Mhz. Still seems like a BIOS issue to me.

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DGroves
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running the part number from the link you provided:

 

https://www.crucial.com/memory/ddr4/ct16g4dfd824a

 

 

shows that crucial states PART IS NOT COMPATABLE WITH YOUR SYSTEM (Prodesk 405 G4)

 

(fill out the will it work boxes with your computer model)

 

https://www.crucial.com/memory/ddr4/ct16g4dfd824a

 

and from the service manual i previous linked to:

 

NOTE: The system does not operate properly if you install unsupported memory modules

 

compatible dimms:

 

https://www.crucial.com/compatible-upgrade-for/hp---compaq/hp-prodesk-405-g4-small-form-factor

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Catzi67
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You are quite correct that Crucial does not list that part as being compatible. However the parts it does recommend are not in line with the specification as printed in the HP Manual e.g. CAS , speed etc. If the PC designer and a third party supplier are in disagreement, I will have to accept the PC designer (HP) as being authoritative.

 

Interesting I originally purchased 'Crucial-recommended' memory which was DDR4-3200 and those dimms gave me reduced speed when fully populated (1866Mhz instead of 2400Mhz). I then consulted the HP manual, looked at the recommended specification, spoke with Crucial technical support who agreed to have the 'recommended' memory returned as it was not in line with the specification printed by HP.

 

Anyway, the question remains, 'Why does the memory speed decrease when populated with the maximum permitted memory'. The memory purchased is 'exactly' as specified by HP. Still seems like a BIOS limitation to me.

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DGroves
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I already told you,......... that due to the additional load on the memory bus caused by filling all ram slots, some systems will decrease ram speeds to maintain stability

 

https://www.google.com/search?q=Why+does+the+memory+speed+decrease+when+populated+with+the+maximum+p...

 

if your system had/has ryzen master installed, sometimes the overclocking must be done from that application only due to how the OEM configured the system/bios but i don't think that's the case here

 

also keep in mind that 

1. crucial WORKS WITH HP in validating ram for systems they do not do it alone

2. memory makers constantly change memory chips, causing memory resellers to delist older modules that use chips that are no longer available and that newer replacement chips unless validated by HP or the chip maker may or may not work the same

3. keep in mind that HP could also be at fault by not documenting the fact the system will run slower if all banks are filled

 

4. you can google this "ram slow if all banks filled" yourself it's not a new issue

 

https://www.google.com/search?q=Why+does+the+memory+speed+decrease+when+populated+with+the+maximum+p...

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Catzi67
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Unfortunately, can't install Ryzen master as it is 'prohibited' according to the installer.

 

I think you are probably correct that filling the memory slots causes the system to lower memory speed. 

 

However it would be nice for HP to confirm this in their documentation or even, heaven forfend, allow the user to override. 

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DGroves
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the intel memory controller is extremely forgiving when it comes to ram, but lags behind the ryzen 3x 5x memory controllers when it comes to performance.

 

 unfortunately, with this speed comes a greater intolerance in the ryzens cpu's memory controller

 

you might want to contact crucial support and see if they have any "LR" dimms for your system "LR" stands for "load reducing"

 

and it's usually used on high capacity dimms  mostly found in servers/workstations that have a large ram capacity

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