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PostPosted: Sun Apr 10, 2016 6:50 am 
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I've spent most of the weekend reading up on DDR2 RAM looking to upgrade my EX495 to 4GB.

So it turns out that there are four key items
    - Not ECC (error correcting code)
    - Unbuffered or unregistered memory
    - Cannot be double sided 16 chip RAM (the high density stuff that is sold on ebay marked AMD only)
    - Supported speed / timings

More on the 2x16 chip issue
The Ex490/495 uses a G33 chipset - Datasheet at http://www.intel.com/Assets/PDF/datasheet/316966.pdf
Page 354 lists the supported DDR2 memory configurations according to the JEDEC standards
• DDR2 DIMM Modules:
    ⎯ Raw Card C - Single Sided x16 un-buffered non-ECC
    ⎯ Raw Card D - Single Sided x8 un-buffered non-ECC
    ⎯ Raw Card E - Double Sided x8 un-buffered non-ECC

Notes:
    - If you see a photo on ebay of a high capacity stick with 16 chips on one side, most likely it'll be Double sided x16.
    - The G33 does support DDR3 in a Double Sided x16 configuration, but the EX490/495 does not support DDR3 (the motherboard manufacturer must choose to support one or both on a single motherboard), so this point is moot.

It seems at some point AMD decided to support (OCZ launch article at http://www.theinquirer.net/inquirer/new ... d-am2-cpus ) the Raw Card H - Double Sided x16 mode for RAM, presumably to keep some life in their DDR2 chipsets, or just because they were sharing so much tech between server chips and desktop. I'm not entirely sure if the Raw Card H standard is meant to be only for Registered and/or ECC RAM, but it's not entirely relevant as the mode is completely unsupported on the mediasmart server. It probably is worth mentioning here that the reason this high density RAM is so cheap, is that it tends to use chips which are commonly found on ECC RAM which is used in servers, where the 2x16 configuration has much wider support.

Then there are a few points of possible confusion:
The first is Kingston KVR800D2N6/4G RAM, datasheet - http://www.kingston.com/dataSheets/KVR800D2N6_4G.pdf, which started off with 8 chips to a side, but it seems at some point they re-released it as a 16 chip per side module (either that or the ebay RAM is fake). The spec sheet does have a disclaimer of Note: The module defined in this data sheet is one of several configurations available under this part number, so I'll take the ebay shops at their word that it's legit.

The second, which isn't really relevant to the mediasmart servers, is that physical layout of chips doesn't matter - it's the wiring. A chip could have 8 chips on a side and be wired as 1x16 or it could have 16 on a side and be wired as 2x8. The Intel G33 supports both, so the point is moot for this discussion - it does not however, ever support 2x16

The final is that the Intel spec sheet (again page 354) says that the maximum supported memory size is 2GB, however I believe that is simply because there were no 256MB chips available at the time (especially with multiple reports of functioning 4GB sticks), so they showed what was possible with current tech.

More on speed / timings
The part which shouldn't really be an issue, but it might come up, is that RAM can have up to 4 JEDEC profiles - memory frequency and CAS latency settings (SPD tab of cpu-z). There is an unlikely possibility that the BIOS will think that none of these settings are OK and therefore will dislike the RAM, although it may be able to be manually configured. See Section 5 of http://www.ocfreaks.com/ram-overclockin ... -tutorial/
The G33 chipset supports memory data transfer rates of 667 MHz and 800 MHz for DDR2 (page 28 of the spec sheet). Because DDR2 https://en.wikipedia.org/wiki/DDR2_SDRAM transfers 2 bits of data on each rise and fall of the clock, all of the below are true for the two speeds:
    - 166/200 MHz Memory clock
    - 333/400 MHz I/O Bus clock
    - 667/800 MHz Memory data transfer rate
    - PC2-5300 / PC2-6400 after the rounded maximum data rates (although some manufacturers round the first up to PC2-5400).

Alternate high density definition
There is some commentary on the

In conclusion
So all in all it's been a lot of reading over the last few days to get my head around all of the various numbers that get thrown about. I'd love some feedback if someone knows a bit more about the topic, or has experience with 2x16 chips that do work or 2x8 chips that don't. Otherwise I hope other EX490/495 owners this is a useful bit of information


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