[Todd Madson]

Remember me?

I was the guy who had the leaking cooling unit that let the processors
overheat, they blew, the power supply blew and so did the motherboard.

They replaced the power supply, both processors, motherboard,
cooling unit and cooling unit housing.

That was last month.

Today I came home to find my powermac operating quite strangely and
I rebooted it.

It now produces two white flashes followed by a pause, then more of
the same and does not boot. Well, it does but something is very broken...

The machine has 2.5 gigabytes of ram, the original 512 megs of ram
that apple supplied with the computer in two 256 meg sticks in addition
to four 512 meg sticks of Corsair Value Select memory which has been
pretty much flawless up until now.

I figured it might be ram so I removed all of the ram save the twin
256 meg sticks and placed them in the bottom slot of both upper
and lower slot banks and booted. Same thing - white flash, pause
white flash and long pause.

Then I tried one pair of the two 512 meg sticks in the bottom two
slots as well as the other slots. No joy.

So I finally put them in the following configuration:

slot
slot 256
slot 512
slot 512

slot
slot 256
slot 512
slot 512

This configuration boots but something is terribly, terribly wrong:

System configuration reads:

Ram:

J11 empty
J11 empty
J13 256 megs of pc3200u-30330
J14 256 megs of pc3200u-30330
J41 256 megs of pc3200u-30330
J42 256 megs of pc3200u-30330
J43 empty
J44 empty

I'm obviously going to have to call Apple in the morning but it seems like
something in the memory controller or memory itself went badly awry
during the day.

Since the last incident I've had the computer (and it's peripherals)
connected to a heavy duty isobar power surge suppressor so I'm
not sure what could have happened here.

Well anyone? Ideas?

[svtcontour]

Oh that cant be good. Hmmm. It sounds like the logic board. Will the system startup with one piece of RAM? If so, try the one piece of ram slot by slot and once booted, see what it reports that ram as - if its the correct size or not.

If it does work with one piece of ram and reports it correctly, then try each piece of memory one at a time. If all pieces allow the machine to start up and are recognized properly, then I'd say the problem was never the ram itself as all pieces would then have checked out fine. Would then be the logic board for sure.

[Todd Madson]

Problem:

G5 computers require ram to be installed in matched pairs.

With lowermost slot in bank a and b filled and none else:
blinks white twice, pauses, repeat.

With lowermost and next lower slot in bank a and b filled:
blinks white twice, pauses, repeat

With the current configuration:
Boots, claims 1 gb of ram installed despite 2.5 gb installed.

I'll be calling Applecare today. Frustrating.

[svtcontour]

Damn...didnt know that you couldnt fire up the machine on one DIMM. Thought it was only in pairs to increase bandwidth but might still start with one.

Hmm what will happen then you think? Will it be supported under warranty or are you going to have to pay? I dont even want to know how much that will cost.

[Todd Madson]

Still under Applecare so they'd better cover it. It's definetely to the point
where I don't think I can trust this machine as a long term machine.

If they repair it again I'm going to try to sell and cut my losses.

[Razgriz]

I would be willling to bet that you have a loose connection somewhere so if you havent already solved the problem try opening up the computer and check for loose connections.

[FurryOne]

Originally Posted by Todd Madson 

Remember me?

So I finally put them in the following configuration:

slot
slot 256
slot 512
slot 512

slot
slot 256
slot 512
slot 512

This configuration boots but something is terribly, terribly wrong:
Well anyone? Ideas?

Todd, I've got an idea. Look again at your logic board. Memory is added in pairs starting with the two middle slots, as such...

====== 4
====== 3
====== 2
====== 1

====== 1
====== 2
====== 3
====== 4

... you add paired memory to the #1's, then #2's, etc. Hope this helps.http://forums.macnn.com/images/smilies/hmmm.gif

[Todd Madson]

Yep, that was it. Stupid.

I thought it was

1 1
2 2
3 3
4 4

But no.