In todays episode we’re going to learn how to fit an LGA771 CPU into an LGA775 motherboard with no brute force!<\/p>\n
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Motivation<\/h1>\n
So why on earth would anyone decide to put an LGA771 Xeon server cpu into a domestic LGA775 motherboard, you may ask?<\/p>\n
Welp, because it’s fun <\/strong>and you get to learn stuff<\/strong>, thats why!<\/p>\n However, the usual argument is that, if you are planning a modest upgrade for your shitty old LGA775 system, not needing the latest and greatest, you can save some money<\/strong> this way. See, there’s lots of Xeon processors<\/strong> in the market right now, and they are all dirt cheap<\/strong>. The interesting thing is that most LGA775 CPUs have Xeons equivalents:<\/p>\n The Xeon I chose, an E5440 SLBBJ. Same speed as a Q9550, but requires less juice, so has a lower TDP. Source: here<\/a> and there<\/a>.<\/p><\/div>\n Some people argue that Intel simply bins Xeons better than the consumer counterparts, so while being essentially the same CPU, the Xeons are more reliable, run colder, and are harder, better, faster, stronger.<\/p>\n The LGA775 market, on the other hand, is filled with pretty expensive CPUs. They’re all usually priced 30\u20ac to 150\u20ac higher than the server versions: Xeons are definitely the best bang for the buck. So the plan usually is:<\/p>\n Some people take advantage of the lower voltages required by Xeons, and choose them not only because they’re cheaper, but because it’s in theory easier to squeeze a bit more speed out of them.<\/p>\n Keeping that in mind, I chose an E0 stepping (later revisions usually lower power requirements of the CPU). Unfortunately, my SLBBJ unit was already running pretty hot at stock voltages and clocks, so I’m leaving it alone for the time being.<\/p>\n LGA775<\/strong> (codenamed Socket T<\/strong>) was introduced by Intel around mid-2004, and used in domestic motherboards<\/strong>. The most popular CPUs running those LGAs are now Core2Duos and Core2Quads.<\/p>\n A year and a half later, in 2006, Intel introduced LGA771<\/strong>, a very similar LGA intended for use in multiprocessor server motherboards<\/strong>, and which can host Intel Xeon processors.<\/p>\n Looking at the official datasheets released by Intel (page 41 here<\/a> and page 52 here<\/a>) , we can check the pinouts of both LGAs, and spot their differences:<\/p>\n If we checked the socket pin assignment one by one, we could see that there’s 76 different pins<\/strong> in total. But most of them are irrelevant (reserved for future uses, etc), they pose no problem for our conversion mod, so we’re left wondering about the colored pins:<\/p>\n The red and green pins are all power pins<\/strong> (VCC, VSS at the top, and VTT at the bottom). There’s hundreds more of them in the LGA, so I’m sure our new CPU won’t mind if we remove just these few.<\/p>\n These pins (L5 and M5) serve different purposes in LGA775 than in LGA771. And this time they are important pins (one of them is the Execute BIST<\/em> pin<\/strong>, Built-In Selft Test, needed to boot). Fortunately, Intel had simply swapped<\/strong> their places in the newer 771 LGA! So it should be relatively easy to re-wire them.<\/p>\n These differing yellow<\/span> shapes<\/strong> can be a problem, since the CPUs from one LGA will not<\/strong> physically fit in the other LGA without some hardware modifications. We’ll get to this later on.<\/p>\n <\/p>\n Uh, in case you’re wondering, I did not<\/strong> personally go over all the pin specifications one by one. But this guy did<\/a>.<\/p>\n In most cases, the CPU will run as-is<\/strong>. This was the case of my 965P-DS3 motherboard.<\/p>\n Sometimes, you may need to manually patch your BIOS<\/strong>, adding the microcode of your specific Xeon model to the internal “whitelist” (so to speak). Additionally, this usually forces your mobo to acknowledge that your Xeon CPU implements the SSE4 instruction set (which can give an extra speed boost in some applications).<\/p>\n I didn’t patch my BIOS just yet… so instead, I decided to steal this screenshot from Google Images. Sue me.<\/p><\/div>\n And in a few rare cases, your motherboard will directly refuse to boot<\/strong> the new CPU, regardless of any BIOS patching you may attempt. In that case, you’re out of luck.<\/p>\n Before attempting to transform your LGA775, search the web and check if your chipset will be happy with a Xeon CPU.<\/em><\/p><\/blockquote>\n In any case, bear in mind that your mobo needs to support the speeds that your specific Xeon choice requires: voltage, FSB speeds, etc. Otherwise you’ll have to resort to underclocking the CPU (sad), or to overclocking your motherboard\/ram (yay! but not recommended).<\/p>\n First, open your tower, remove the heatsink, then the CPU:<\/p>\n There lies my old Core2Duo E4300, overclocked to hell, ready for retirement.<\/p><\/div>\n Now we do what the title says: we hack the LGA775 socket. Literally.<\/p>\n Yes, take a sharp knife or a cutter<\/strong>, and prepare to slash some plastic. The exact bits you have to cut off are the ones colored yellow<\/span> in the LGA775 pinout diagram (scroll back to the beginning of this post). It should end up looking something like this:<\/p>\n Actually, please try to aim for cleaner cuts than the mess you see in this photo.<\/p><\/div>\n The motherboard is ready!<\/p>\n Now we need to hack the Xeon CPU itself. Remember the blue<\/span> pins that had switched places in LGA771? It’s time to revert what Intel did, and get a 775-compatible pinout layout.<\/p>\n If you’re good enough you could try to swap them yourself, using whatever technique you come up with. But the rest of us mortals will resort to buying a ready to use swapper sticker<\/strong>. Search for “775 771 mod” in ebay<\/a>, play safe and buy several of them, just in case you break one in the process:<\/p>\n Be very careful with the sticker, it’s very easy to break its internal wiring.<\/p><\/div>\n So there’s that. Now we simply have to put the Xeon in the LGA, add thermal paste, heatsink, etc:<\/p>\n Yay, we’re done!<\/p><\/div>\n Finally, plug the PSU, pray to Flying Spaghetti Monster, and boot the system!<\/p>\n <\/p>\n Here’s a nice comparison graph of the results. The contenders are:<\/p>\n The benchmarks are:<\/p>\n <\/p>\nTraditional motivation: Money<\/h3>\n
![\"Xeon](\"http:\/\/www.stenyak.com\/wp-content\/uploads\/2014\/02\/xeon-c2q.png\" "\\"Xeon")
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Side motivation: Overclocking<\/h3>\n
Background<\/h1>\n
<\/a>\u00a0<\/a><\/p>\n\n
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Motherboard support<\/h1>\n
<\/a>Procedure<\/h1>\n
<\/a><\/a><\/a><\/a>Results<\/h1>\n
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