Like I said in my previous post, you're looking for the Xeon model 5365 3.0Ghz Quad-Core processor, stepping code SLAED.
These were known in the industry as Clovertown processors, and were basically two Woodcrest 5100-series dual cores combined into one LGA771 package for a total of four cores. Just like the Woodcrest, there was no hyperthreading.
I bought mine on eBay for $150.00 each. The prices have come down considerably on Clovertown CPUs since I bought mine, but they're still not exactly giving them away.
This current eBay auction has a matched *pair* of 5365 SLAED processors starting at $175.00:
http://www.ebay.com/soc/itm/32104691505
Your conversion on the IBM 9228 is a very simple thing.
1. Check that your IBM BIOS is the latest version 1.45. If not, you'll need to download the IBM utility to flash it to v1.45.
2. Remove the two 5150 processors and replace them with the two 5365 processors. Make certain you have clean heatsink/fan units, and that you have an appropriate amount of good (Arctic Silver 5 or better) thermal compound in place.
3. If you're running Windows 7 Pro or Ultimate, you may have to enter MSCONFIG.EXE after rebooting and set the number of processors to 8 under Boot/Advanced Options to make use of the additional 4 cores you added.
That's it! Multi-task, multithread (or both!), to your heart's content!
I'm running the dual Xeon 5365 Quad Cores, 16Gb memory, a 240Gb SSD OS drive, 1.0Tb files drive, 64Gb SSD Pagefile drive, and a Radeon HD6870 in my IBM 9228 Z-Pro, all under Windows 7 64-bit Ultimate. I will eventually go to 32Gb memory for a total of 4Gb/core.
While not a gaming rig, it does rather well at the task, as long as you understand that most games aren't multithreaded (yet). Where it shines is post-processing of large RAW images under Adobe Photoshop CS6 64-bit and Adobe Illustrator CS6 64-bit. As a professional photography student, I'm now working with my Nikon DSLR and HDR images, combining 5 frames from a given composition for best dynamic effect. Adobe will use all 8 cores, plus the video card, to process these images. It's a hoot!
http://mauser98.com/dualclovertowns.jpg