This forum post by the moderator lists 667 as the RAM speed. Personally I would not put any extra money into upgrades in a 14 year old PC. Better to even consider a refurbished newer unit.
From the Optiplex 755 Tech Guide, 800MHz is the max RAM speed for it.
I really don't know that you'll notice a difference in RAM speed between 667MHz and 800MHz simply using the PC.
The only way I know to fix it if you want to pursue it is to return the RAM you just bought. Unless you bought it already, I suggest A-Tech RAM. It comes with a lifetime warranty, is what I ran in my previous 755 and now my 7010. https://www.amazon.com/s?k=optiplex+755+ram+a-tech&ref=nb_sb_noss
By the way, what brand of RAM did you buy? Also, there's been problems in this forum with KVR (Kingston Value RAM). It works for some in Dell's, but not for everybody.
JOcean
9 Legend
•
12.6K Posts
0
June 28th, 2021 16:00
This forum post by the moderator lists 667 as the RAM speed. Personally I would not put any extra money into upgrades in a 14 year old PC. Better to even consider a refurbished newer unit.
cryptic
10 Posts
0
June 28th, 2021 16:00
That’s what dell officially confirmed but there are other forum posts that confirms 800mhz .
bradthetechnut
7 Technologist
•
9.4K Posts
0
June 28th, 2021 17:00
From the Optiplex 755 Tech Guide, 800MHz is the max RAM speed for it.
I really don't know that you'll notice a difference in RAM speed between 667MHz and 800MHz simply using the PC.
The only way I know to fix it if you want to pursue it is to return the RAM you just bought. Unless you bought it already, I suggest A-Tech RAM. It comes with a lifetime warranty, is what I ran in my previous 755 and now my 7010. https://www.amazon.com/s?k=optiplex+755+ram+a-tech&ref=nb_sb_noss
By the way, what brand of RAM did you buy? Also, there's been problems in this forum with KVR (Kingston Value RAM). It works for some in Dell's, but not for everybody.