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Old 09-08-2011, 06:00 AM   #1
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Is there a difference between the memory modules in Z800 and in ProLiant?


We want to buy some HP Z800s and put in as much memory as possible. We would like to put in 12 x 8GB DIMMs =96GB. This is a bit expensive for us. We are using numerically intensive engineering applications which really do use this much, or more, if available.

When I look on the HP site, the 8GB DIMMs for the ProLiant are cheaper than the 8GB DIMMs for the Z800s, and they have a different part number. The JEDEC specifications listed for both are identical in all details as follows
240 pin
Dual Rank

When I asked HP what the difference is they said that the product for Z800 is R9 Registered memory,and that the product for the ProLiant is R5 Registered memory. I have never heard of R5 and R9 registered memory, and have Googled and not a single reference. HP say the pins will be different and they will not fit.

Is this true? Or has he made it up? Has anyone heard of R5 and R9 registered memory?
Old 09-08-2011, 09:29 AM   #2
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HP Manufacture memory for specific products, the motherboards tend to be manufactured with that specification in mind, including DIMM Slots, where the slot to fix the DIMM in will be in different positions depending on the memory required, this difference will even be present between different models of desktop. This also prevents grey market / counterfeit memory being supplied.

Also if you look at HP Part Surfer for 501536-001 / 536890-001 you can see all the compatible products for each DIMM

Although the memory descriptions are similar and on paper they may look the same, they are manufactured for different functions and different products. I wouldn’t ever suggest purchasing server memory for a workstation.

R5 refers to CAS 5 and R9 to CAS 9 memory (The R is an HP thing but refers to CAS) – This refers to the timing or number of clock cycles it takes to perform an indicated function. Generally the lower the CAS number the faster the memory. All being equal though the main problem is still that the memory is developed specifically for the motherboard / Processor / Architecture of either the server or Workstation it is to work for and is not interchangeable between different product sets I’m afraid. The pin configuration, although exactly the same amount of pins, is different in the fact that the guide slot for fitting into the DIMM Slot on the motherboard is in a different place.

Last edited by Linux1000000; 09-08-2011 at 09:49 AM.
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Old 09-08-2011, 10:24 AM   #3
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This is not an independent reply, as you are the HP person who provided the information in the first place,and you have already emailed this reply to me. Thanks but I was hoping for an independent reply actually. Sorry!

I don't know much about this but does HP memory not conform to JEDEC standards? You imply that HP systems are designed to take HP memory only, and that we are therefore locked in to purchasing memory from HP exclusively for HP systems? I was not aware of that? I don't know much about this but I thought that the point of JEDEC was to prevent this, so that others can manufacture compatible memory modules for the market? Actually I have often purchased additional memory for HP systems over the last 15 years from third party suppliers when it was time to upgrade the systems, without having any problems.

Thanks for your reply though!



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