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Apparent Logic Board problems?

pkoch1

pkoch1

macrumors 6502a
Original poster
Oct 3, 2007
527
0
Boston
Hi

I'm trying to sell my old Mac Pro (with no AppleCare), but I want to get all of the problems figured out so nothing comes up after the buyer buys it.

My RAM configuration is as follows:

2x2GB, 4x1GB

It never reads the correct amount of ram (8GB). It fluctuates between 2GB and 6GB depending on my configuration, but recently it's only been 2-4GB. I'm currently troubleshooting which RAM trays/RAM slots/RAM sticks are giving me problems. It's looking like only the innermost two slots on the upper RAM tray are working. It doesn't matter which tray i insert on the upper tray slot. It only recognizes the innermost two slots.

I've done many AHT hardware tests on the logic board (well, the entire computer), which haven't found any problems.

That said, it looks like both my trays are okay, and all of my RAM sticks are okay, just the computer is only recognizing those inner slots.

Any advice? Could it possibly just be a software issue, or is it looking like a problem with the LB? I just really don't want to carry my Mac Pro all the way to the Apple Store. (I have to walk there)

Thanks in advance!
 
It will help tremendously if you would tell us which Mac Pro you are talking about.

The correct ram configuration from the 2006 Mac Pro to the 2008 Mac Pro are very different and from the sounds of it, it seems you are installing the ram incorrect.
 
Pressure said:
It will help tremendously if you would tell us which Mac Pro you are talking about.

The correct ram configuration from the 2006 Mac Pro to the 2008 Mac Pro are very different and from the sounds of it, it seems you are installing the ram incorrect.
Click to expand...

This is the Early 2008 Mac Pro. I have successfully had all 8GB of RAM recognized before, and one day it was not all there anymore ;).

EDIT: And I made a mistake. The upper tray recognizes all 4 slots, but only recognizes the 2GB sticks as being 1GB. The lower tray recognizes nothing.
 
pkoch1 said:
This is the Early 2008 Mac Pro. I have successfully had all 8GB of RAM recognized before, and one day it was not all there anymore ;).

EDIT: And I made a mistake. The upper tray recognizes all 4 slots, but only recognizes the 2GB sticks as being 1GB. The lower tray recognizes nothing.
Click to expand...

Try and put all four 1GB modules in the upper tray and the two 2GB modules in the lower tray.
 
pkoch1 said:
Each slot on the upper tray reads 1GB, the lower tray reads nothing.
Click to expand...

So it reads all four 1GB modules?

Try with the two 2GB modules alone by taking out the top tray and replace it with the lower tray holding the two 2GB modules.

And then try with the upper tray holding the four 1GB modules in the lower slot to see if it detects the ram.

After that I would try swapping the trays to see if one of the trays is defective.
 
Pressure said:
So it reads all four 1GB modules?

Try with the two 2GB modules alone by taking out the top tray and replace it with the lower tray holding the two 2GB modules.

And then try with the upper tray holding the four 1GB modules in the lower slot to see if it detects the ram.

After that I would try swapping the trays to see if one of the trays is defective.
Click to expand...

Yeah, I've tried all that. When it's just the 2GB modules in the lower tray, the computer doesn't boot and the power light flashes. No matter which physical tray I use, the one on top is the only one recognized. I've also tried putting the 1GBs in the innermost slots and the 2GBs in the outermost slots on the upper tray, and it still only reads them as 1GB. Weird, right? This is why I'm surprised that the hardware test found nothing.

I tried with a different user account too, and got the same results.
 
pkoch1 said:
I've also tried putting the 1GBs in the innermost slots and the 2GBs in the outermost slots on the upper tray, and it still only reads them as 1GB. Weird, right? This is why I'm surprised that the hardware test found nothing.

I tried with a different user account too, and got the same results.
Click to expand...

Who did you buy the extra ram from? I had a similar problem with some OWC ram. They were great to deal with and replaced them.
 
surflordca said:
Who did you buy the extra ram from? I had a similar problem with some OWC ram. They were great to deal with and replaced them.
Click to expand...

I think it all came from OWC. I think I'd have to determine that the RAM was bad first though before they would replace anything.

It might be the RAM, but even so, the entire bottom tray doesn't recognize any RAM.
 
Old thread, problem came back!

So I replaced my Logic Board back when this all happened. (I worked at an authorized repair center so I did it myself.) It worked for a while, but now it doesn't again. Also, the USB ports on the front aren't working, but I understand that is a different board that is probably also broken. The bottom slot (no matter which tray) recognizes nothing, but the top slot works (kinda). The top slot sees all RAM as being 1GB sticks whether they are 1GB or 2GB. Weird. Any ideas?
 
its not the logic board that is broken, it's the RAM riser board.





also, when USB on the front doesnt work on macpro, its 99.5% that you forgot to connect the internal cabels to it, or connected them incorrect.
 
Cindori said:
its not the logic board that is broken, it's the RAM riser board.
also, when USB on the front doesnt work on macpro, its 99.5% that you forgot to connect the internal cabels to it, or connected them incorrect.
Click to expand...

Well, like I said, no matter which riser it is in, only one slot works.
(I might have misspoke and said the top one works. It's the bottom one) Each riser works in the bottom slot, but not normally. The first two slots occupied by 2GB chips read as one 1GB chip in the first slot. No matter which riser.

The USB problem had been happening before the LB replacement. I reseated the cables back then, but it didn't fix anything. Everything is connected correctly now, and now they work about 10% of the time. Maybe something is wrong with the cable and it's getting a spotty connection.
 
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