Problem with ram upgrade mac pro 3.1 early 2008

[thejuanvisu]

Hi
yesterday i bought 2x8GB ram FB ECC 5300F ram modules and when i insert them, on the riser i can see 2 red lights and the computer doesnt recognise the rams. ¿What can i do?

 

[tsialex]

Hi
yesterday i bought 2x8GB ram FB ECC 5300F ram modules and when i insert them, on the riser i can see 2 red lights and the computer doesnt recognise the rams. ¿What can i do?

You can't configure the risers. If you install an incompatible DIMM, the red led will lit.

2008 Mac Pros only can use dual rank FB-DIMMs. Quad rank memory don't work, check if your new memory is dual or quad rank.

 

[thejuanvisu]

You can't configure the risers. If you install an incompatible DIMM, the red led will lit.

2008 Mac Pros only can use dual rank FB-DIMMs. Quad rank memory don't work, check if your new memory is dual or quad rank.

How can i now if they are dual rank or not?
the ram i am usig is this: hmp31gf7emr4c-y5d5 ac

 

[tsialex]

How can i now if they are dual rank or not?
the ram i am usig is this: hmp31gf7emr4c-y5d5 ac

Quad rank. It's the 4Rx4 of the label:

 

[thejuanvisu]

Quad rank. It's the 4Rx4 of the label:

View attachment 827548

Oh, so the problem is the ram... The ebay seller is sellig this rams as mac pro 2008 compatible, i think i`ll have to ask for a refund....
Thanks for the help

 

[tsialex]

Oh, so the problem is the ram... The ebay seller is sellig this rams as mac pro 2008 compatible, i think i`ll have to ask for a refund....
Thanks for the help

I never had a quad rank memory working with my 2008 Mac Pros. Someone here, years ago, posted about a quad rank memory that supposedly works, but it was never confirmed. Even 2010/2012 Mac Pros have lot's of problems with quad rank memories…

 

[thejuanvisu]

I never had a quad rank memory working with my 2008 Mac Pros. Someone here, years ago, posted about a quad rank memory that supposedly works, but it was never confirmed. Even 2010/2012 Mac Pros have lot's of problems with quad rank memories…

something strange is that cpu-z detects 20GB Ram(the 4 originals and the 16 i added), i dont know why...

 

[tsialex]

something strange is that cpu-z detects 20GB Ram(the 4 originals and the 16 i added), i dont know why...

CPU-Z is reading the SPD info via I2C.

Dual rank memory has 2Rx4 on the label, btw.