What DDR2 is this?

[xjas]

A guy on my local site is selling these 4GB modules:

I'm confused because they look like registered modules (buffer chip in the middle), but the P designation implies un-registered, and that part number comes up as unreg in a few places when searching around. Also, the notch key is the same as standard DDR2 as far as I can tell. Which is it? Is that "buffer" chip something else, or just sitting dormant?

My board (nForce 590 / socket AM2) can take ECC unregistered/unbuffered. I'm guessing these aren't what I want, but if they are, it'd make my day. Advice needed.

 

[Chuck(G)]

This is what Amazon says:

Mfr Part Number: M393T5160QZA-CE6
Type: DDR2
Capacity: 4 GB
Speed: PC5400 667MHz
Size & Bit: 512 x 4
Pins: 240pin
ECC: Yes
Registered: Yes
Chip: Samsung
Rank: 2
Chips: 18
CL 5
RoHS Compliant

 

[xjas]

^^ thanks; that confirms what I thought it was, but why is it designated "5300P" (parity) rather than "R" (registered)? Am I missing something or did they just mark it wrong?

Rant: ECC registered is worth peanuts everywhere, while non-ECC unregistered goes for about double the price, especially for 4GB sticks. ECC unregistered is apparently made of unicorn teeth. Why is the specific one of something I want, always the expensive one??

 

[Ole Juul]

Rant: ECC registered is worth peanuts everywhere, while non-ECC unregistered goes for about double the price, especially for 4GB sticks. ECC unregistered is apparently made of unicorn teeth. Why is the specific one of something I want, always the expensive one??

I suspect that's for older stuff. Server operators can't afford to run something as small as 4 GB so it's worthless to them, and desktop boards generally can't use it. So you're complaining about something useless being cheaper than something useful.

 

[Unknown_K]

P means parity (ECC)
F or FB means fully buffered
R means registered
U means unbuffered

 

[xjas]

^^ which is why I'm confused; what seem to be Registered (R) DIMMs are marked Parity (P). I'm wondering if they did something like built all modules the same, but changed the firmware to make them registered or unregistered. Does that even make sense?

 

[Unknown_K]

Registered RAM has an extra chip between the RAM chips and the memory controller to make things more stable with more RAM DIMMs (also adds a wait state). You can see the extra chip in the middle of the DIMMs.
If the RAM chips are grouped in 9's you have ECC, 8 means non ECC.
You can have ECC ram that is (R)egistered (extra chip) or (U)nbuffered without the extra controller chip.

FB RAM has the notch in a different location because the modules are different then other RAM. FB uses serial interface between the memory controller and RAM buffer, normal DIMMs use a parallel bus architecture. This means FB DIMMs have more wait states and also use more electricity so run hotter.