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[nanofrog]

Registered memory is the same as unbuffered memory?

No.

There's an additional chip on the PCB of an RDIMM that allows for the higher capacity to be used by the system (has to do with signal stability, as it reduces the load on the memory controller that would be presented by the additional memory chips without it).

Officially speaking via Intel, a 2009 Quad Core 2.66 GHz Mac Pro can only take 1066 MHz, ECC, unbuffered, and unregistered memory?

Officially speaking, Yes.

You can use 8GB RDIMM's in the 2009, but they'll still only run at 1066MHz (in this particular case, that's all the CPU's memory controller will run at; but even if the CPU was capable of running memory at 1333Mhz, the firmware is actually fixed to 1066MHz, rather an using SPD timings).

Read on another thread that 1333 MHz can work, that MP would automatically downgrade the speed to 1066 MHz.

Correct. They'll just run at 1066MHz, so go with whatever is cheaper to get the necessary/desired memory capacity. 😉

 

[Luba]

Thanks for the info, very helpful!! Just few questions on abbreviations and other tech info. 🙂

PCB = ?

RDIMM = Registered DIMM, correct?

SPD = ?

So definitely want RDIMM as it adds stability which translates to increased speed since memory controller doesn't need to work as hard?

Just curious if Apple came out with new firmware a 2009 Mac Pro could handle 1333 Mhz memory? If yes, why would they limit it? 1333 Mhz would cause too much heat?

No.

There's an additional chip on the PCB of an RDIMM that allows for the higher capacity to be used by the system (has to do with signal stability, as it reduces the load on the memory controller that would be presented by the additional memory chips without it).


Officially speaking, Yes.

You can use 8GB RDIMM's in the 2009, but they'll still only run at 1066MHz (in this particular case, that's all the CPU's memory controller will run at; but even if the CPU was capable of running memory at 1333Mhz, the firmware is actually fixed to 1066MHz, rather an using SPD timings).


Correct. They'll just run at 1066MHz, so go with whatever is cheaper to get the necessary/desired memory capacity. 😉

 

[Vylen]

The Printed Circuit Board.. stereotypically green - the actual thing that electronic tid-bits are placed onto.

as for SPD... its referring to the Serial Presence Detect chip. DIMMs usually have these and contain the recommended timings for the RAM. So nanofrog is saying the firmware is designed to ignore the SPD and run on whatever it's programmed to.

 

[nanofrog]

RDIMM = Registered DIMM, correct?

Yes.

And UDIMM = Unbuffered DIMM

So definitely want RDIMM as it adds stability which translates to increased speed since memory controller doesn't need to work as hard?

The reason for using Registered memory is when you're after a capacity that's not really possible using UDIMM's alone, as there's too much of a load on the memory controller for it to be stable (results in performance and capacity loss).

RDIMM is faster under a specific case for DDR3 based memory controllers as currently designed, which is in dual channel configurations (i.e. 2x UDIMM's per CPU).

But the primary goal of RDIMM is to get capacity where it's needed for the intended usage (i.e. greater than 24GB per CPU in MP's, or if triple channel can be utilized <very rare>, allows 24GB in that configuration). So 24GB in triple channel or 32GB per CPU is what you'd use 8GB RDIMM's for (RDIMM's are expensive compared to UDIMM's <cost/GB>, so true need dominates the use of it). For smaller capacity requirements, UDIMM will work just fine.

Hope this clears things up on RDIMM. 🙂

Just curious if Apple came out with new firmware a 2009 Mac Pro could handle 1333 Mhz memory? If yes, why would they limit it? 1333 Mhz would cause too much heat?

They won't. 1333MHz memory was more expensive, and it allowed them to keep the parts bin smaller, as few CPU's they selected would have been able to use it for the 2009 systems (most maxed out at 1066; not like there was all that many to begin with). So they simplified things by installing 1066MHz memory, and set a fixed memory frequency in the firmware (saved development time).

They did fix this in the 2010's (CPU's with memory controllers that can utilize 1333MHz memory will work, and ship with 1333MHz memory), but that firmware has not, nor will be released for the 2009 models, even though it would work if they did. 🙁

 

[Luba]

So to summarize 2009 can take UDIMM or RDIMM, (RAM doesn't come both UDIMM and RDIMM, correct?), but get RDIMM as that's faster for MP. Crucial offers UDIMM for MP??

Get 1066 Mhz or higher, whatever is cheaper.

Get ECC (Error Correction), OWC talks about how theirs is 72 bit, higher bit the better?

Get thermal sensor.

OWC offers multi-channel, good to get multi-channel?

Crucial mentions their memory is 1.5V, lower voltage the better?

So what's are the spec's to go for? Never realized there's so many aspects to RAM. 🙂

Yes.

And UDIMM = Unbuffered DIMM


The reason for using Registered memory is when you're after a capacity that's not really possible using UDIMM's alone, as there's too much of a load on the memory controller for it to be stable (results in performance and capacity loss).

RDIMM is faster under a specific case for DDR3 based memory controllers as currently designed, which is in dual channel configurations (i.e. 2x UDIMM's per CPU).

But the primary goal of RDIMM is to get capacity where it's needed for the intended usage (i.e. greater than 24GB per CPU in MP's, or if triple channel can be utilized <very rare>, allows 24GB in that configuration). So 24GB in triple channel or 32GB per CPU is what you'd use 8GB RDIMM's for (RDIMM's are expensive compared to UDIMM's <cost/GB>, so true need dominates the use of it). For smaller capacity requirements, UDIMM will work just fine.

Hope this clears things up on RDIMM. 🙂


They won't. 1333MHz memory was more expensive, and it allowed them to keep the parts bin smaller, as few CPU's they selected would have been able to use it for the 2009 systems (most maxed out at 1066; not like there was all that many to begin with). So they simplified things by installing 1066MHz memory, and set a fixed memory frequency in the firmware (saved development time).

They did fix this in the 2010's (CPU's with memory controllers that can utilize 1333MHz memory will work, and ship with 1333MHz memory), but that firmware has not, nor will be released for the 2009 models, even though it would work if they did. 🙁

 

[Vylen]

So to summarize 2009 can take UDIMM or RDIMM, (RAM doesn't come both UDIMM and RDIMM, correct?), but get RDIMM as that's faster for MP. Crucial offers UDIMM for MP??

Get 1066 Mhz or higher, whatever is cheaper.

Get ECC (Error Correction), OWC talks about how theirs is 72 bit, higher bit the better?

Get thermal sensor.

OWC offers multi-channel, good to get multi-channel?

Crucial mentions their memory is 1.5V, lower voltage the better?

So what's are the spec's to go for? Never realized there's so many aspects to RAM. 🙂

It's unusual naming, but Registered RAM also means Buffered RAM... conversely Unregistered means Unbuffered. But, for whatever reason, the common nomenclature is to say Registered and Unbuffered.

And yes, get one with a thermal sensor. Previous (old) posts have indicated that if you put RAM without a thermal sensor into the machine, the Mac will consider it a hardware failure and bug you 😛

As for the other stuff - that's all techno "rhetoric"...

The ECC is standard... and so is the voltage.. i.e. they're within specifications (the bare minimum?) and aren't anything special. ECC RAM utilising more than 72bits would be really awesome but really expensive 😉 DDR3 SDRAM is designed to have a 1.5V power supply.

The multichannel stuff is just a consequence of replacing all your RAM with the same kind from the same seller (i.e. you get the same sticks). It's more to do with the computer itself since it has the capability rather than the RAM you install.

 

[nanofrog]

So to summarize 2009 can take UDIMM or RDIMM, (RAM doesn't come both UDIMM and RDIMM, correct?), but get RDIMM as that's faster for MP. Crucial offers UDIMM for MP??

It can take UDIMM, RDIMM, and non-ECC memory. The trick is, you cannot mix these types.

And No, there's no single stick that's both UDIMM and RDIMM compliant (one or the other, as an additional chip is involved if it's RDIMM).

Get 1066 Mhz or higher, whatever is cheaper.

Get ECC (Error Correction), OWC talks about how theirs is 72 bit, higher bit the better?

Get thermal sensor.

The easiest thing to do, is order a memory kit from either OWC or Trans Int'l, as the specialize in Mac Pros (guarantee their hardware, and test that what the sell does in fact work properly).

Just be careful with mixing memory types, which includes the 4GB UDIMM sticks sold by OWC (they state that it will not work with the OEM memory that shipped with the system or the smaller UDIMM's they sell).

Others that have bought different brands of 4GB UDIMM's have had success with mixing it (Crucial for example) not sure what the difference is for sure, but the thermal sensor may be out of range in terms of it's voltage output).

But it's still easier IMO to stick with either OWC or Trans Int'l.

OWC offers multi-channel, good to get multi-channel?

Don't worry about this; it's what I was getting to about the different channel configurations (i.e. most software cannot take advantage of triple channel configurations <provides additional bandwidth for memory>), but the extra capacity of filling the 4th DIMM slot per CPU will have a notable effect (reduce or eliminate the need for page outs = using the disk as virtual memory, and it's much slower).

Which is why capacity trumps bandwidth for almost all usage patterns (there are exceptions that the triple channel configuration can be utilized, but it's really rare on workstations right now).

So make sure you get sufficient capacity for your software, and don't worry about triple channel.

Crucial mentions their memory is 1.5V, lower voltage the better?

That's the voltage spec the memory is supposed to run at in the '09 & '10 systems, so there's nothing special about it (but earlier forms of DDR3 designed to run at higher voltages, and wouldn't work properly if at all - came out before any of the LGA1366 parts = Nehalem i7-9xx and Xeon 3500/5500 series <before anything Westmere>).