MP 1,1-5,1 MacPro doesn't boot after RAM upgrade

Caesar_091

macrumors 6502
Original poster
Jan 18, 2005
257
10
Italy
Hi,

I have recently bought 24 more GBs of RAM (3x8GB) for the Mac Pro in signature.
The "old" RAM was installed in slot no. 1, 2 and 3 and I have installed the three new modules in slots no. 5, 6 and 7.
Once installed if I try to boot the Mac up the Sleep Indicator Light (SIL) start blinking and the computer doesn't boot up.
If I install only the old three modules or only the new three modules the Mac start up regularly.
I also tried to mix the modules (1 new and 2 old in the first three slots, etc etc) but no way.

Any suggestion?

I'm returning the new modules but I really would like to expand the RAM. Should I buy 3 new modules identical to the current ones to avoid any further risk of incompatibility?
 

chrfr

macrumors G3
Jul 11, 2009
8,505
2,729
Hi,

I have recently bought 24 more GBs of RAM (3x8GB) for the Mac Pro in signature.
The "old" RAM was installed in slot no. 1, 2 and 3 and I have installed the three new modules in slots no. 5, 6 and 7.
Once installed if I try to boot the Mac up the Sleep Indicator Light (SIL) start blinking and the computer doesn't boot up.
If I install only the old three modules or only the new three modules the Mac start up regularly.
I also tried to mix the modules (1 new and 2 old in the first three slots, etc etc) but no way.

Any suggestion?

I'm returning the new modules but I really would like to expand the RAM. Should I buy 3 new modules identical to the current ones to avoid any further risk of incompatibility?
Mac Pros can use either buffered/registered or unbuffered/unregistered RAM, but they cannot use both at the same time. I’d suspect the new RAM differs from the old in that respect.
 

MacUser2525

macrumors 68000
Mar 17, 2007
1,912
269
Canada
Mac Pros can use either buffered/registered or unbuffered/unregistered RAM, but they cannot use both at the same time. I’d suspect the new RAM differs from the old in that respect.
You are correct that would be my thoughts on his problem as well. To upgrade the ram it needs to be all of the same type you can have the density problem doing this, the lower then higher density with the chips on both sides of the modules, for something that is supposed to be standardized there are a lot of variations that will not work together. Technologies companies are so wonderful. I remember the good old days where it was in kb for ram and you could not even be guaranteed identical sticks would work if you filled too many of the slots and god forbid you wanted to combine different sizes, now get off my lawn....
 

Caesar_091

macrumors 6502
Original poster
Jan 18, 2005
257
10
Italy
Thnaks guys for the reply. I have no idea about those specs... but I can take a some pics!

This is one the old module (all the same):

old_RAM.png


And this is one of the new:
new_RAM.png
 

Caesar_091

macrumors 6502
Original poster
Jan 18, 2005
257
10
Italy
Just installed 3x8GB modules of registered RAM and now the MP is running smoothly.
@chrfr thanks again for your reply!