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User profile for user: luanna
luanna Author
User level: Level 1
8 points

Fastest RAM for PowerMac G5

I have a late 2005 model Power Mac G5. I read on the net (forgot the site) that this model could use PC2-4200, PC2-5300 and PC2-6400. So I went out and bought 8 Gb of PC2-6400. I've installed it and in my System Profiler, it's reading that the Speed is PC2-3200. I read on a thread on this forum that the computer doesn't recognize RAM this high so it knocks it down to the lowest speed that it reads, which is 3200. I just realized that I had also installed 2 GB of PC2-5300 and it was reading as PC2-3200 ( I thought it was 3200 all along, but got corrected at Microcenter, where I bought it). The original ram is 4200, btw.

Am I to understand that the only ram this computer reads properly is 3200 and 4200? There is no firmware update or anything to make it read anything above 4200??

Thanks in advance.

Dual 2.3 GHz Power Mac G5, Mac OS X (10.4.11)

Posted on Feb 24, 2009 10:39 PM

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User profile for user: japamac
japamac
User level: Level 7
24,400 points

Posted on Feb 25, 2009 3:45 AM

Hi-

Fastest RAM for dual core G5?

240-pin DDR2 SDRAM DIMMs that are 1.8 volt, unbuffered, 8-byte, ECC and non-ECC, and DDR2 533 MHz (PC2-4200) compliant.
The main logic board of the Power Mac G5 computer has 8 slots of DDR2 SDRAM expansion for unbuffered, DDR2-533 (PC2-4200) dual inline memory modules (DIMMs) for a maximum memory of 16 GB. The Power Mac G5 accepts both ECC and non-ECC DIMMs. Each DIMM can contain 256 MB (non-ECC only), 512 MB, 1 GB, or 2 GB of double data rate synchronous dynamic RAM (DDR2 SDRAM). At least one pair of the RAM expansion slots contains factory installed DIMMs. The Power Mac G5 supports CAS read latencies of 4 and 5.

Anything beyond the specified RAM is a waste. The Mac cannot use anything faster than the specified RAM.

The misreporting may be due to the fact that the EEPROM does not have an ID that the Mac understands. The RAM may, or may not, be fine. It isn't the right RAM, so testing is all that you can do.

Testing with Rember or Memtest is recommended. If errors show, remove the RAM, and replace with the proper specification, guaranteed Mac compatible RAM.

The faster memory should be backward compatible, but it does not provide any benefit whatsoever.
The RAM CAS and other timing factors are all controlled by the Mac firmware. There is no update available, or necessary.

Use only G5 specification, guaranteed compatible RAM.
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User profile for user: japamac
japamac
User level: Level 7
24,400 points

Feb 25, 2009 3:45 AM in response to luanna

Hi-

Fastest RAM for dual core G5?

240-pin DDR2 SDRAM DIMMs that are 1.8 volt, unbuffered, 8-byte, ECC and non-ECC, and DDR2 533 MHz (PC2-4200) compliant.
The main logic board of the Power Mac G5 computer has 8 slots of DDR2 SDRAM expansion for unbuffered, DDR2-533 (PC2-4200) dual inline memory modules (DIMMs) for a maximum memory of 16 GB. The Power Mac G5 accepts both ECC and non-ECC DIMMs. Each DIMM can contain 256 MB (non-ECC only), 512 MB, 1 GB, or 2 GB of double data rate synchronous dynamic RAM (DDR2 SDRAM). At least one pair of the RAM expansion slots contains factory installed DIMMs. The Power Mac G5 supports CAS read latencies of 4 and 5.

Anything beyond the specified RAM is a waste. The Mac cannot use anything faster than the specified RAM.

The misreporting may be due to the fact that the EEPROM does not have an ID that the Mac understands. The RAM may, or may not, be fine. It isn't the right RAM, so testing is all that you can do.

Testing with Rember or Memtest is recommended. If errors show, remove the RAM, and replace with the proper specification, guaranteed Mac compatible RAM.

The faster memory should be backward compatible, but it does not provide any benefit whatsoever.
The RAM CAS and other timing factors are all controlled by the Mac firmware. There is no update available, or necessary.

Use only G5 specification, guaranteed compatible RAM.
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User profile for user: TANK289
TANK289
User level: Level 1
10 points

Apr 20, 2009 9:46 AM in response to The hatter

Hi at all,
I'm in the similar situation, someone sold me some ram for my powermac G5 dualcore 2.3 late 2005 thta is recognized at pc2 3200 but it was 667 ddr2 pc 5300
My mac did't have crash or kernel panic , but afthere some weeks when I saw that it'snot show correctly I remove it and my backfan(that goes back the logic board) afther some days started to speed up, and stay normaly around 2500.
So I bring the mac to the apple certified center, they test it, reset ecc. and they say thts it's normal.
It's all good.
The fan is still noising and still around 2500.

I would like to try resetting or reinstalling or semething else to the firmware. it's possible?
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User profile for user: TANK289
TANK289
User level: Level 1
10 points

Apr 22, 2009 6:16 AM in response to TANK289

Nobody know?
In pc there are bios that can be reflash and updated, in mac there are firmware right?
So the firmware in mac how can be reinstalled or reset or something else?
I read that the logic board of apple dont have a chip where there are the information of firmware, but this information are hide on the HD. This is right?
If it's right reinstalling the osx it would reinstall the firmware too. No?

Let me know please.
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User profile for user: japamac
japamac
User level: Level 7
24,400 points

Apr 22, 2009 6:25 AM in response to TANK289

Nobody know?

You cannot change the performance settings of RAM in a G5.
So the firmware in mac how can be reinstalled or reset or something else?

Not by the user.
I read that the logic board of apple dont have a chip where there are the information of firmware, but this information are hide on the HD. This is right?

No, this is wrong.
If it's right reinstalling the osx it would reinstall the firmware too. No?

No it would not.
The firmware is in chips on the logic board and in each hardware item (hard drive, optical drive, graphics card, etc).
Some devices may be hacked, but a RAM timing hack for the logic board ROM and memory controller is unlikely and would probably kill the machine and/or its ability to boot to OS X.
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User profile for user: TANK289
TANK289
User level: Level 1
10 points

Apr 22, 2009 7:24 AM in response to japamac

Thank for your clarify answer Japmac.
But if the firmware on the logic board become corrupt ther's will be a way for restore it ?
Another question about ram : I hear that ram like 667 sold as compatible for G5 late 2005 that use 533 can couse firmware corruption. It's possible? And if this happen ? I immage that the firmware would be restore. it's correct?
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User profile for user: The hatter
The hatter
User level: Level 9
60,990 points

Apr 23, 2009 1:53 PM in response to direwolf8

And how during normal operations and even OS updates - at this point in time especially - is the Open Firmware or firmware for the G5 going to become corrupt so it needs to be restored? normally, only during firmware update itself can that happen, and only then can the firmware restore CD be of use.

Corrupt nvram does happen. ATTO first alerted me that when swapping PCI cards in/out or changing memory. Also, the G5 has some type of problem in NOT recognizing say a swapped out hard drive (still acts as though the old drive is still present).

People sometimes walk away confused to what firmware even is or when it gets updated or changed.
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Fastest RAM for PowerMac G5

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