Q: Compatible Xeon processors for Mac Pro 1,1

The Woodcrest uses a LGA 771 sock and only processors that use the same socked can work but not all will work.

You are better off purchasing a 2009 or later Mac Pro. Very few apps would use all 12 cores and the 2006/2007 can only take quad core processors.

Upgrading Mac Pro (2006) to 8-core Processor?

http://www.xlr8yourmac.com/feedback/2006MacProDual5355CPUs.html

Report: 2006 Mac Pro (MacPro 1,1) Dual X5355 CPU Upgrade
(Low-Cost Dual Quad-Core CPUs)

Posted: Dec. 13, 2013

Yes as one of the links in my previous reply said:

Xeon 5355s are drop in replacements for the 5150s in the '06 MP. You will find more info here:

Hardmac.com - Le "Macbidouille" in English - Upgrading CPUs of a Mac Pro to Quad Core Xeons;

Apple's Mac Pro - Upgrading CPUs, Memory & Running XP - AnandTech -- Your Source for Hardware Analys…

That isn't true. You can in fact install Intel Xeon x5365 3.0GHz Quad Core processors after doing a firmware update/efi modification to change the Mac Pro 1,1 to a Mac Pro 2,1. This will in turn enable you to run 10.8/10.9/10.10 and even El Capitan, breathing some life into the machine

Thanks for this answer, Spencer! I have an old 2006 Mac Pro 1,1 with quad core and 16gb RAM, wanting to do one of "those" upgrades to even install El Cap or Sierra to use as my back up video or photo touch up computer for a different office!

I installed blue tooth, wifi, put a 1gb VRAM graphics card in a while back, and an SSD for the OS drive... but I want to REBUILD this thing as MUCH as POSSIBLE!!!!

Do you have ANY links to where I could find a list of the PROPER parts for this mac and suggestions of WHERE to buy them? I just wanna make sure I get the right processors, and junk to make it work right!!

Thanks so much!!

Would THIS one work? I want as many cores as I can possibly have for this old mac... https://www.amazon.com/3-0GHz-Intel-Quad-Core-1333MHz-Socket/dp/B004EET158

With Adobe, Dropbox, and even iWork being cloud-based... I can work ANYWHERE!! I can put my mac pro in one office and keep my new iMac beast with 4gb VRAM, 32gb RAM, 3TB fusion, 5k, 27" retina, 4.0GHz i7 at home! Ya know?