MP 1,1-5,1 3.1 Riser Dimm 1 red led

[AppleRussMac]

i really need help!!

Recently acquired a Mac Pro 3.1 2.8 octo. Came with 2x2GB 800Hz, 2x1GB 800Hz and 2x1GB 667Hz. About this Mac only recognises 6GB total. No matter what configuration I do, changing both risers and ram, the bottom riser is always showing a red led for dimm 1 and thus the Mac isn’t using that riser.

Any ideas on what to do next?

 

[Alex Sanders74]

Likely the ram chip in Dimm 1 slot is bad or doesn't like the slot. Try removing it and changing slot order. Of course, be sure to pair them up correctly between trays. Mixing Dimm speeds between 800 and 667 isn't ideal either. Get all 800 for this MacPro, otherwise everything will downclock to the 667 speeds.

Also, try a PRAM reset after reseating the Ram.