Thank you for reaching out to Dell Community Forum.
Please find the details on Page 27 and 150 from the below link:
please click my DELL-username and send me a Private Message with the Dell Service Tag number and your email address.
Note: please don't mention the service tag or email id on the public forum as it contains your personal information
You need a matching CPU "S SPEC" and heatsink. DELL FD841 PROCESSOR HEATSINK PRECISION WORKSTATION 690 T7400 You cannot mix speeds or S Spec on the CPU.
3.0Ghz Harpertown Xeon Processor Service Kit, X5450 SLBBE
3.3GHz Harpertown Xeon Processor Service Kit, X5470
3.33GHz Wolfdale Xeon Service Kit, X5260, 1333
3.4GHz Harpertown Xeon Service Kit, X5492 .
3.4GHz Wolfdale Xeon Service Kit, X5272