Memory upgrade in G5 dual 2.3 (late 2005)--speed weirdness

HI-

The System Profiler is just reporting what is coded in the EEPROM of the RAM.
I would suggest that the RAM is not up to the specifications required by the G5, and would best be returned, and replaced with RAM that is of the proper specification.
It's more than just what's printed on the label:

DIMM Specifications

Dual Core G5 DIMM spcecifications general.

The failure of the RAM to be recognized properly in hardware tests also supports the lack of proper spec theory.
I would be leery of trusting my data to be processed through this RAM.

Hi, I topped my G5's memory to the full 16GB's! don't ask me why. but you should have bought the same type of memory that was already in your G5 (PC2 4200 DDR2 533MHz) I reckon for some reason if you put in higher frequency modules the G5 defaults to safe settings.

Joe (",)

These are the ones I used
Kingston KTA-G5533/4G
Total cost: £134.14 Which is pretty good I reckon.

Joe

Is this just a matter where System Profiler (and Hardware Test) are not able to correctly identify the RAM because the EEPROM SPD value is 667, but the memory otherwise works fine?

Maybe. Not knowing for sure is the problem.

Or will the EEPROM issue somehow result in memory errors?

That is doubtful.

Is the SPD value for identification only, or does it actually affect the way the memory interacts with the CPUs somehow?

It has everything to do with the way the firmware tests, recognizes, and the kernel tasks utilize the RAM.

Apple created a narrow set of specifications for G5 memory for a reason. Claiming a misreport of non-specification RAM is an Apple bug is funny. What about DDR2-533 is so hard to understand?
DDR2-667 will do no extra good if, otherwise, problem free.

Playing outside of the spec's, is like playing outside of the law- you don't know if, or when, you're going to get caught.

Stay with Apple spec'd, quality RAM, or, accept that not all will appear as it should, and possibly, not work as it should.

I know the higher speed doesn't provide any advantage since my system can't move data faster than 400 MHz, but aren't faster DDR2 chips normally backward compatible with slower DDR2 chips?

This is true. This is also why Crucial, among others, sell DDR2-667 memory to G5 owners.
However, I have never understood the logic behind this. A dual core G5 can only run DDR2-533 RAM.
Also, timing parameters are narrow, and set by the SPD of the firmware. Anything outside of the specified requirements for RAM is not only unnecessary, it borderlines on unsupported modification of the system.
Crucial also sells DR2-533 RAM. I don't know what the thinking can be, other than there is a better margin on the DDR2-667 RAM......

I actually would have gotten DDR2-533s but Crucial's "Memory Advisor" utility identified these 667s as being "guaranteed-compatible" and Crucial's web site doesn't even list the DDR2-533s anymore that I could see.

*Guaranteed compatibility* will imply that +ALL functions+ are normal. Misreporting is not normal, as far as I know, and I would consider the memory to be incompatible.

That post from the guy who works at TechWorks/Buffalo Technology saying they have verified the misreporting on three Macs seems to support this.

The firmware is looking at the EEPROM of the RAM, expecting to see narrowly defined parameters. Anything outside of this, will either result in a failed POST at boot, or result in possible errors in reporting. My contention would be that the information within the EEPROM, or, the structure of the DIMM assembly, does not meet the specifications as defined by Apple engineers, nor does it present itself to the firmware in a way that the RAM properly reports.

If this is confirmed on three machines, of how many thousands, what is it about those three machines that is special?

Or, could it be the DIMMs that were used in the test just happen to be the culprit.

I've read on this site and elsewhere that Crucial sells quality memory that meets Apple specs. I believe I even saw one of your older posts recommending it.

This is true. I also recommend OWC, and add Crucial to offer a purchaser a choice in vendor.

BTW, OWC only offers DDR2-533 DIMMs for the dual core G5.

What do they understand that the others don't?

Do you think Crucial's memory has gone down in quality since then?

I wouldn't go that far. I do know that chip batches vary, DIMM construction varies, and makers are always trying to get the broadest compatibility possible within a given product. That means, any Windows machine, Linux machine, Sun Machine, Unix Machine, etc. is targeted to use a given product.
Given the variety of needs, firmware, and other architectural differences of all the machines, it isn't possible to satisfy all machines with one EEPROM. Mac's are particularly difficult, as the firmware has been refined, over the years, to require RAM that adheres to the specifications set forth.
This only serves to protect the best interests of the end user...... a stable system, and error free data handling.

I know the higher speed doesn't provide any advantage since my system can't move data faster than 400 MHz, but aren't faster DDR2 chips normally backward compatible with slower DDR2 chips?

This is true. This is also why Crucial, among others, sell DDR2-667 memory to G5 owners. However, I have never understood the logic behind this

Cost of manufacturing and stocking different chips.
when there were problems with PC2100 (early MDD G4) they stopped producing and were pushing PC2700s - made to be backward compat and to higher standards. Same happened with PC2700 and PC3200 later on.

The Mac Pro can use DDR2 667 or 800MHz but there, the 2008 model year is designed off 200MHz ( * 4) but no value or option of installing say 1200MHz memory.

SPD code. A PC only needs a basic CAS Latency value of '3' to boot and get into the BIOS where you can then add and edit, with a Mac it must support other values to work and so it can work with other chips.

Other things that vary from batch to batch but play a role like voltage and just "chip DNA" come into play.

Apple did "something" during the G5 model revisions that came out summer 2004. The specs all "looked the same" but caused problems for Crucial and every other memory chip maker, and took over a month. We had some good - and heated - discussions at the time - both here, and on other forums and chatrooms. Tightening of spec tolerance is my best guess. Someone from Crucial even created an AD account to respond directly.

Stealth upgrades, wherever it occurs, is the bane of support.

In a number of cases, and what I recommend anyway since that summer, is to always first try with your new RAM to insure it works properly in the system, alone, with even OEM memory removed, to establish it is compatible.

Then add back other memory. Sometimes even when they "should" they just don't, the variance in timing, frequency, voltage and how a chip operates vary (and there can be differences in a single chip).

they are letting me return the 5300 chips for a full refund even though the tech insisted this IS an Apple firmware issue

If you bought it as Apple-compatible memory and they claim that it's compatible with the Macintosh, it doesn't matter whose issue this is. The memory doesn't work on that machine.

You can often buy the very same memory from them in generic form or for a"PC" for a few dollars less, but then they might not take it back if it doesn't work on your mac. I guess it's a good reason to pay the extra few dollars.