There are noticeably few articles, if any, about the 2006 and 2007 Mac Pros, that help you diagnose memory issues. I am changing this by documenting my own experiences with my primary computer, a Mac Pro 2,1. This article should help you recognize any memory symptoms with your Mac Pro and resolve them quickly.

This article is also very inclined toward my experiences using a 64 GB memory kit on my Mac Pro 2,1, so for those of you using a 64 GB kit in your own Mac Pro 1,1 or 2,1, this article will especially be helpful! Look through the questions and answers listed, and see which apply to you.

What Type of Memory Does a Mac Pro 1,1/2,1 Use?

• 667 MHz DDR2 ECC fully buffered DIMM (FB-DIMM) PC2-5300f Micron Memory sticks
• Eight FB-DIMM slots on two memory riser cards (four slots per card) supporting up to 64 GB of main memory (16 GB According to Apple, 32 GB “unofficially”, and 64 GB according to Intel but with some Mac OS restrictions)
• 256-bit-wide memory architecture
  

  Pictured here, is an 8 GB PC2-5300f 667 MHz DDR2 SDRAM FB-DIMM. An 8×8 GB config (8 of these) is the maximum memory a Mac Pro 1,1 or 2,1 is capable of using.

  

How Much RAM Can My Mac Pro 1,1/2,1 Handle?

• This strongly depends on your operating system.
• 32 GB max., Mac OS X 10.4 – 10.7.5
• 64 GB max., Mac OS X 10.8 – 10.11.6

Why the Differences in RAM Ceilings?

The changes reflected in Mac OS X 10.8 Mountain Lion and above, are from the kernel the Mac Pro boots into. Since the Mac Pro 1,1 and 2,1 are fully 64-bit computers, merely fitted with a 32-bit EFI, they’re totally capable of booting into a 64-bit-clean OS, which is why a modified Boot.efi file works as a workaround. Since you will be booting into a 64-bit Kernel on a 64-bit OS as of Mac OS X 10.8 and later, the RAM ceiling is lifted to the maximum that the Intel 5000X chipset memory controller can handle- 64 GB of RAM.

What Is the Intel 5000X Chipset?

• It is the PCIe/RAM memory controller for your Mac Pro; it’s an integrated Intel component on your logic board.
• The 5000X memory controller chipset has a TDP Max of 32.4W, a maximum memory bandwidth of 21 GB/s, natively supports 533 MHz and 667 MHz memory, has 4 total channels (2 riser cards with 2x dual channel pairs each), is of the PCIe v1.1 revision (this means these Mac Pros have PCIe v1.1, not v1.0!), and has a maximum temperature tolerance of 105°C.

Before Diagnosing Your Mac Pro 1,1/2,1 RAM, Remember:

• Make sure all the RAM is seated in place
• Make sure the riser boards are snugly plugged into their slots, fully in
• Riser cards and surrounding area must be free of dust
• CMOS battery isn’t dying
• The power supply isn’t having any issues
• Reset PRAM by powering up your Mac, pressing: Command + Option + P + R upon startup, as well as using the Reset switch behind the top right area of the RAM cage.
• Please wear some sort of antistatic device

Common Issues with RAM Memory in the Mac Pro 1,1/2,1:

1. One or more sticks don’t show up
2. Specific riser cards don’t work/specific riser card slots don’t work
3. Red LED’s on riser board/Fans being loud
4. Temp sensor failure
5. Really hot RAM sticks
6. Quarter/Half/3 quarters of the memory shows up as used in the Activity Monitor, even though there is nothing running which is using that amount of RAM
7. There is no startup chime.. only beeping sounds.

1. One or More Sticks Don’t Show Up

• Make sure that both sticks match and are of the standard Mac Pro 1,1/2,1 spec (further up in article)
• They must be seated properly (both plastic pins on each side “click” into place)
• Check for red LEDs on the riser board
• Swap the RAM sticks around to different slots on the board, or swap places on the riser card slots, and see if results change.

2. Specific Riser Cards or Slots Don’t Work

• Swap the top and bottom riser boards, and see if anything changes.
• If the same riser board which previously worked on the bottom now works on the top (or vice versa), take out all the RAM sticks and swap them to different slots on the riser cards.
• If only the bottom 4 work or only the top 4 work, irrespective of whichever riser card you use, swap all the RAM sticks between the different slots on the riser cards, just like in the previous bullet point.
• If after swapping around the sticks there are memory errors but both riser cards work again, then your riser cards are fine, and you’ll need to swap RAM spots until it works, or, you just have one or perhaps a few bad memory stick(s).
• If after swapping around the sticks and the riser boards, the same 4 sticks don’t show up on either the top or bottom riser cards, chances are it’s a logic board going bad. See if you can get a spare riser card, and go from there. Don’t fret, Mac Pro 1,1 logic boards are $30 on eBay.
• If after swapping around riser boards and memory sticks, one riser board consistently doesn’t work, irrespective of whichever bay it’s plugged into, chances are it’s a bad riser card. Mac Pro 1,1/2,1 riser cards are cheap on eBay!

3. Red LED’s on the Riser Board, Fans Are Loud

• If you’re still booted into the OS, check your RAM temperature. You can do this using an app called Macs Fan control
• If after checking the temperature, they all read 127°F, there’s a 50/50 chance you have a failed temperature sensor. This is probably why your fans ramped up very loudly (for no reason) recently, because of this failed temp sensor (could also be a glitch). Refer to #4 and #6 on this list if you see this, it might help.
• Shut down the machine, let it cool off, swap around RAM sticks, and start it up.
• Make sure the RAM stick pairs match up (in spec, frequency, etc;)
• Make sure there’s a proper heatsink installed on the RAM
• Make sure there’s no dust inside the RAM slot
• Make sure the riser card isn’t full of dust

4. Temp Sensor Failure (and How to Determine It)

• This occurs when a temperature sensor has consistently failed to report the accurate temperature and is irrespective of the various glitches other hardware/software may have on it.
• If after checking the temperature, they all read 127°F, there’s a 50/50 chance you have a failed temperature sensor. This is probably why your fans ramped up very loudly (for no reason) recently, because of this failed temp sensor. Swap around RAM sticks, see if any changes occur. It also helps to have extra riser cards handy, and another Mac Pro to test this riser card out. Reset the SMC (button is behind the top riser card slot, right corner. There will be 2 buttons, you can hit both of them)
• If after doing all of the basic diagnostics (swapping riser cards and RAM sticks, SMC reset, PM reset, etc.) the riser card shows up with consistently unusual temperature readings (especially if you have sticks on the board with the bad sensor, swapped out from the other board) chances are the riser card needs replacement.

5. Really Hot RAM Sticks

• Make sure the RAM has proper heatsinks.
• If you are using 3rd party RAM (such as a 32 or 64 GB Micron kit) with very thin heatsinks, try to replace them with Apple heatsinks. Old Mac Pro RAM kits are cheap when you buy low capacity kits. I’d suggest getting a 4 GB kit of original Apple RAM (with Apple heatsinks) and swapping out the Apple heatsinks onto the larger RAM kit (or whichever one you want to use). These original Apple heatsinks are designed for this Mac Pro and have more surface area to cool the RAM, since the airflow is lower in the Mac Pro, as to keep it quiet. Most computers that have this type of memory are very loud due to high-speed fans, that’s why the 3rd party heatsinks are so thin.
• Make sure there’s thermal paste on the chip die in the middle of the RAM stick, or that it isn’t old (it most likely is)
• Make sure there’s no dust buildup
• Use Macs Fan Control to ramp up the fans in Mac OS

6. One-quarter, Half, or Three-quarters of Memory Shows Up as Used in Activity Monitor, Despite Nothing Actually Using That Amount

• The reason this is happening is that you have ECC RAM, and your system detects a fault with RAM but is able to recognize it (however, cannot use it). This is most likely not the case. I have been able to resolve this issue by simply swapping out a riser card from another machine.
• Check to make sure your RAM temperature is in the normal range
• Check for red LEDs
• Check to make sure all RAM is seated
• Reset SMC, PRAM, and swap riser cards + RAM sticks

7. There Is No Startup Chime… Only Beeping Sounds.

• One beep, every 5 seconds: Your Mac Pro isn’t detecting any RAM, period. Make sure your RAM is seated properly, and that your riser cards are, too. Make sure your RAM matches, and make sure there’s no dust piled up
• 3 Beeps, with a 5-second pause (repeating): Your RAM doesn’t pass the data integrity check. Potentially bad RAM memory.

Hopefully, this article helps you diagnose the RAM in your Mac Pro 1,1 or 2,1. This is an actively updated article, as I intend for it to reflect my experiences and solutions, as many solutions/observations came from my own experiences since not many Mac Pro 1,1 and 2,1 memory articles are out there.

keywords: #macpro2006 #macpro2007

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