LGA 771 to 775 compatibility checker
Pick a Xeon and your board’s chipset and support list; get a pass, check or fail strip with the reasons.
Build sheet
Possible, with things to confirm: Xeon E5450
- NoteSocketXeon E5450 is an LGA 771 chip: it needs the adapter sticker, and the two key tabs on the LGA 775 socket must be cut off.
- PassFSBIntel P45 supports 1333 MT/s; this CPU runs at 1333 MT/s.
- PassQuad coreIntel P45 supports quad-core chips at this FSB.
- Pass45 nmIntel P45 officially supports 45 nm (Penryn family) processors, given a BIOS that knows them.
- CheckBIOSLook up your board's CPU support list for a 45 nm Core 2 Quad (Q8000 or Q9000 series) at 1333 MT/s and the BIOS version that added it.
- CheckTDPThis CPU is rated 80 W. Check the highest TDP your board lists.
- NoteMicrocodeDesktop BIOSes rarely carry the LGA 771 microcode for 10676 or 1067A. If you see an update prompt or instability, add it (see the microcode guides).
The checker answers one narrow question: given a processor from our database and what you know about your board, which parts of the match are documented, which do you still have to confirm, and which rule it out? It works from chipset support as Intel published it, plus three facts only you can supply. It never sees your board, so read a clean result as a paper check, not a promise.
How to use it
- Pick the processor. LGA 771 chips (the Xeons that need the adapter sticker) come first, native LGA 775 chips second.
- Pick the board chipset. This is the northbridge, not the board model: CPU-Z shows it on the Mainboard tab, and the board manual lists it. The 945 and nForce families are split by bus speed (the nForce 790i has its own entry), so pick the exact name. If you cannot find it, choose "Not sure / other".
- Answer the desktop twin question. The twin is the LGA 775 chip with the same core, bus speed and stepping as your Xeon, such as a Q9650 for an E0-stepping E5450. Choose "Yes, at the same FSB" only if the maker's CPU list shows one.
- Pick the highest TDP the board lists: find the hungriest chip on the list and choose the nearest option, or leave it on "Not sure".
- Tick the box if it is a Dell, HP, Lenovo or Intel-brand board.
Our guide to checking whether a motherboard supports a processor shows how to find the exact board and its list.
What each row means
Pass means the documented facts line up. Check means something is unknown or outside Intel's specification, and you need to confirm it. Fail means a documented limit rules the chip out or makes it a poor bet. Note is information that never changes the verdict.
| Row | Labels | What decides it |
|---|---|---|
| Socket | Note or Pass | Note for an LGA 771 chip (sticker and socket tabs), Pass for a native LGA 775 chip |
| FSB | Pass, Check, Fail | The CPU's bus rating against the chipset's official maximum; Check where a faster bus is unofficial, as on the P45 at 1600 MT/s |
| Quad core | Pass, Check, Fail | Four-core chips only; Check if Intel lists quads only at a lower bus speed (the G31 at 1066 MT/s) |
| 45 nm | Pass, Check, Fail | 45 nm chips only; Check where support depends on the board maker's BIOS |
| BIOS | Pass, Check, Fail | Your answer to the desktop twin question |
| TDP | Pass, Check, Fail | The CPU's TDP against the highest TDP you picked |
| Microcode | Note | LGA 771 chips only; names the CPUID signatures the BIOS needs microcode for |
| OEM board | Check | Only when the box is ticked |
FSB is the front-side bus between CPU and northbridge, rated in MT/s (million transfers per second). TDP, thermal design power, is the heat in watts Intel tells board and cooler designers to plan for; a TDP Fail means the chip is rated above anything the maker listed, so the voltage regulators may run hot or the BIOS may refuse it. With "Not sure / other" as the chipset, the FSB, quad-core and 45 nm rows give way to a single Chipset row marked Check.
The headline sums up the strip. Any Fail gives "Not a good match for this board". Checks without a Fail give "Possible, with things to confirm". Only Pass and Note rows earn "Looks compatible on paper".
The BIOS row carries the most weight. A modded Xeon boots by passing for a chip the board already knows, so a missing twin sinks the plan even when every chipset row passes. Page 2 of the LGA 771 to 775 guide explains the twin rule and the chipset table behind these rows.
Worked example: the default settings
The tool opens with an E5450 (LGA 771, four cores, 45 nm, 1333 MT/s, 80 W) on an Intel P45 board, the CPU list on "Not checked yet", the TDP on "Not sure" and the OEM box clear:
| Row | Label | In short |
|---|---|---|
| Socket | Note | LGA 771 chip: adapter sticker, and cut the two key tabs |
| FSB | Pass | P45 supports 1333 MT/s; the CPU runs at 1333 MT/s |
| Quad core | Pass | P45 supports quad-core chips at this FSB |
| 45 nm | Pass | Officially supported, given a BIOS that knows the chips |
| BIOS | Check | Look for a 45 nm Core 2 Quad (Q8000 or Q9000 series) at 1333 MT/s on the list |
| TDP | Check | Rated 80 W; check the board's highest TDP |
| Microcode | Note | Desktop BIOSes rarely carry the microcode for 10676 or 1067A |
No OEM row appears. Two Checks and no Fail give the headline "Possible, with things to confirm: Xeon E5450".
Both Checks are homework, not warnings. Say your board's support list tops out with a Q9650, Intel's 95 W quad at 1333 MT/s, which only came in the E0 stepping. Set the twin question to "Yes, at the same FSB" and the TDP to 95 W. The BIOS row turns to Pass, the TDP row reads "80 W fits within the 95 W your board lists", and the headline becomes "Looks compatible on paper".
The microcode note stays, because nothing on the form tells the tool whether your BIOS holds the Xeon's update. 10676 and 1067A are the CPUID signatures of the C0 and E0 steppings. Our guide to finding a chip's CPUID, stepping and sSpec tells you which you have, and the LGA 771 Xeon microcode page covers adding the update.
What it cannot tell you
The checker knows chipsets, not boards. Two P45 boards can differ in BIOS support, regulator design and revision, and only the maker's CPU list speaks for a specific one. The chipset figures follow Intel's datasheets as Wikipedia's list of Intel chipsets summarizes them, and a few entries still group chipsets whose boards differ, such as the catch-all "NVIDIA nForce 6xx / 7xx (other)". It does not check stepping either: a "Yes" to the twin question assumes you matched C0 or E0 as well as the class.
Community reports vary, too. Owners describe success and failure on the same chipset, and the widely read mod threads call X38, X48, Q35 and Q45 boards riskier without saying why. The tool leaves those reports out: a report about someone else's board is not a fact about yours.
Questions
Why does it ask about a desktop chip instead of the Xeon?
Board makers never listed LGA 771 Xeons, since the boards were never meant to take them. The closest documented evidence is support for the LGA 775 chip that shares the Xeon's core, bus speed and stepping.
Can a board with a Check row still run the chip?
Often, yes. A Check means a fact is missing or the pairing sits outside Intel's specification, as a 1600 MT/s Xeon on a P45 does. Confirm the item, change your answer, and the row updates.
Why is microcode a note and never a Fail?
Many boards boot a Xeon without its microcode and show an unknown CPU, while others stop with a microcode error. The tool cannot tell which group your BIOS falls into, so it names the CPUIDs to look for.
My chipset is not in the list. What now?
Choose "Not sure / other" to see the processor-side rows, then read the board maker's CPU list. AnandTech's 2007 roundup of 45 nm board support found no VIA or SiS chipset with official 45 nm support, so treat those boards as poor hosts.
Does a Pass on every row mean the board will boot?
No. The socket cut, the sticker, the microcode and the board's own quirks still decide the first boot, and page 5 of the guide sorts the usual failures by symptom.