Weird G5 unrecognised RAM issue

[BarnacleGrim]

I've been wondering lately whether there's something wrong with either my memory, or my G5's memory. It's a 1st generation 2x2 GHz machine, and it came with 512 MB of RAM preinstalled. So I bought an extra two 512 MB DIMMS and installed when I set up the machine, making a total of 1.5 GB. But lately I've been seeing only 1 GB in the "About This Mac" window.

I did a memory test in Tech Tool Pro, it found two working 512 MB DIMMS.

Sunday, June 13, 2010 6:47:30 PM Europe/Stockholm
Passed


DIMM0: Empty

DIMM1: Empty

DIMM2: J13
Size: 512 MB
Type: DDR SDRAM
Speed: PC3200U-25330

DIMM3: J14
Size: 512 MB
Type: DDR SDRAM
Speed: PC3200U-25330

DIMM4: Empty

DIMM5: Empty

DIMM6: Empty

DIMM7: Empty



10101010 Check

This test works by writing the binary pattern 10101010 consecutively throughout the memory matrix, reading and verifying each pattern after it has been written.

01010101 Check

This test works by writing the binary pattern 01010101 consecutively throughout the memory matrix, reading and verifying each pattern after it has been written.

11110000 Check

This test works by writing the binary pattern 11110000 consecutively throughout the memory matrix, reading and verifying each pattern after it has been written.

00001111 Check

This test works by writing the binary pattern 00001111 consecutively throughout the memory matrix, reading and verifying each pattern after it has been written.

11111111 Check

This test works by writing the binary pattern 11111111 consecutively throughout the memory matrix, reading and verifying each pattern after it has been written.

00000000 Check

This test works by writing the binary pattern 00000000 consecutively throughout the memory matrix, reading and verifying each pattern after it has been written.

Passed

So I figured the original two 256 DIMMS were fried, so I pulled the 512 ones and tried starting it up, which it did normally. I ran Tech Tool again with passing results:

Sunday, June 13, 2010 7:07:30 PM Europe/Stockholm
Passed


DIMM0: J11
Size: 256 MB
Type: DDR SDRAM
Speed: PC3200U-30330

DIMM1: J12
Size: 256 MB
Type: DDR SDRAM
Speed: PC3200U-30330

DIMM2: Empty

DIMM3: Empty

DIMM4: Empty

DIMM5: Empty

DIMM6: Empty

DIMM7: Empty



10101010 Check

This test works by writing the binary pattern 10101010 consecutively throughout the memory matrix, reading and verifying each pattern after it has been written.

01010101 Check

This test works by writing the binary pattern 01010101 consecutively throughout the memory matrix, reading and verifying each pattern after it has been written.

11110000 Check

This test works by writing the binary pattern 11110000 consecutively throughout the memory matrix, reading and verifying each pattern after it has been written.

00001111 Check

This test works by writing the binary pattern 00001111 consecutively throughout the memory matrix, reading and verifying each pattern after it has been written.

11111111 Check

This test works by writing the binary pattern 11111111 consecutively throughout the memory matrix, reading and verifying each pattern after it has been written.

00000000 Check

This test works by writing the binary pattern 00000000 consecutively throughout the memory matrix, reading and verifying each pattern after it has been written.

Passed

I put the 512 MB DIMMS back in and tried starting up, but it went into Open Firmware. I typed mac-boot and got the question mark folder icon. I restarted and it booted, but without a chime. Same results as the first test. I'll try another reboot after I post this. Does anyone have an idea why I'm being cheated of 512 MB of RAM?

 

[johnklos]

It could be something wrong on the motherboard. Try using the other four slots and see what you get.

 

[BarnacleGrim]

DIMM0: Empty

DIMM1: Empty

DIMM2: J13
Size: 512 MB
Type: DDR SDRAM
Speed: PC3200U-25330

DIMM3: J14
Size: 512 MB
Type: DDR SDRAM
Speed: PC3200U-25330

DIMM4: J41
Size: 256 MB
Type: DDR SDRAM
Speed: PC3200U-30330

DIMM5: J42
Size: 256 MB
Type: DDR SDRAM
Speed: PC3200U-30330

DIMM6: Empty

DIMM7: Empty

That did it! I was doubtful at first, seeing that the inner slots worked on their own, but moving the 256 MB DIMMS outside of the 512 MB DIMMS solved the problem, got the chime back and the system feels more responsive now. However the manual does say that DIMMs must be installed from the centre and outward. Should I expect problems in the future? Especially since I'm thinking of upgrading the machine.

 

[johnklos]

Get a flashlight and some compressed air or a non-static paint brush and check out the memory slots. Sometimes in machines which are dusty moving DIMMs can force a little dustball into a DIMM socket and cause a pin (or two or three) to not make contact. If you can see anything inside of the slots, use the compressed air or paint brush to get it out, and you may have fully working slots again.

 

[BarnacleGrim]

Dust comes to mind, it was quite bad after 6 years in a house with carpets on every floor and bookshelves on every wall. I used half a can of dust-off (I hear it causes memory problems when used internally xx( ) when I moved it downstairs. But the RAM was installed when it was clean out of the box and never moved until today. It worked fine with only one pair of DIMMS at the time.

 

[phreakout]

BarnacleGrim,

On your G5, it lists Bank 0 through Bank 7, right? And the instructions recommend that you install from the center two slots (Bank 3 and Bank 4) and work out, right? Try moving the cards so that you have the 512 sticks in 3 and 7, while the 256 sticks are in 2 and 5. This should assure fast performance. That's my suggestion.

73s de Phreakout. :rambo:

 

[BarnacleGrim]

The G5 has two banks of 4 slots each. One bank has odd numbered slots and the other bank has even numbered, starting at the centre and moving outwards. So DIMM0 and DIMM1 are the innermost slots and DIMM6 and DIMM7 are the outermost slots.