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PrefetchW and Processors

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  • Processors
  • Windows 8
  • CPUs
Last response: in CPUs
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November 14, 2013 4:06:11 AM

Hi all...
Windows 8.1 in the 64-bit version only supports processors that, among other specifications permit use of PrefetchW instructions.
Which processors allow these instructions?

More about : prefetchw processors

a c 393 à CPUs
November 14, 2013 9:32:00 AM

If it's fast enough to run Windows 8, it can run Windows 8.
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a b à CPUs
November 14, 2013 7:59:40 PM

Almost all processors support prefetch nowadays, the only CPUs that cant run windows 8 are the very old Pentium 3 and 4s, and alot of the older Single core CPU's like the Celerons. They generaly can't handle it.
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November 26, 2013 5:58:43 PM

Well I've got dual Intel Xeon Narcona 3.6Ghz 64-bit cpu's, which do not support prefetchW. Actually this instruction is implemented as a NOOP on newer Intel CPU's, it was originally an extension to the amd64 instruction set to allow optimizations on AMD processors. So why do you say that my Xeon CPU cannot handle Windows 8.1, while Windows 8.0 was fine?

Do you feel that windows 8.1 become so backwards that it needs more than 2MB cache, dual 3.6Ghz 64-bit Xeon (with PAE, NX, SSE2), and 8GB RAM, because it lacks the ability to do a NOOP using prefetchW?

Or has Microsoft made a serious error to require prefetchW?
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April 5, 2014 11:00:49 PM

For Anyone with Same Problem:
my Windows XPSP3 Dell Dimension 4700 "project" computer upgraded to max of 4G RAM on OEM Mobo (0M3918), BIOS A10 (the very last revision). generally listed compatible CPU upgrades "supported" for this system are all Pent 4 HT 5xx, with various other sporadic reports of 6xx working.

my results:
Pent 4 HT 520: (OEM) no 64bit support, never even tried W7 or W8.1
Pent 4 HT 541: ($5 ebay) successful W7 64bit, successful W8.1 32bit, fails W8.1 64bit due to lack of "PreFetchW"
Pent 4 HT 631: ($5 ebay) would not boot - DOA vs Incompatible. this is a "Cedar Mill" (65nm architecture) not "Prescott" (90nm)
Pent 4 HT 662: ($20 ebay) same as for 541: again no "PreFetchW" support.
I doubt any compatible CPU for my system will support W8.1 64bit. i might send the 631 back just see if, in fact, it was simply DOA. the release date for the 631 was Q1'06 compared to the 662 released Q4'05 - so it might be more capable since it was released later, but i doubt it - i think the 90 vs 65 nm is the main difference.

as near as I can tell, the only way to verify a CPU's full capabilities are to actually install the CPU and run "Coreinfo.exe". this is also confusing as downloading Coreinfo to desktop then R-clicking it to "run" opens a cmd window for only a split second then it is gone. I was able to keep Coreinfo open by Start>Search>"run">"cmd">C:\Users\(your user name)_ at the blinking underline cursor fill in EXACTLY: "C:\Users\(your user name)\Desktop\Coreinfo.exe then hit [enter]. this all seemed a bit redundant but it worked (remember - I tinker but I am certainly no coder or system administrator). PreFetchW is toward bottom of list and will have a " - " (not supported) or a " * " (supported).
I could not find this specific information anywhere on any search, including Ark-Intel.

I was using a W7 "Upgrade" license and a "Full Retail" W8.1 (no attempt at W8 at any time). I also did a complete hard drive wipe w DBAN. All of this is really so I can help my mom with her W8 computer - I want to get familiar w W8-8.1 so when I have her hold her iPhone facing her monitor w FaceTime running, i can see what she's doing and already have some W8 problem-solving experience. this is my poor-man's version of remote assistance.

i hope this helps anyone with a skill level similar to mine
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a b * Windows 8
a c 198 à CPUs
April 5, 2014 11:46:53 PM

jamieff said:
Well I've got dual Intel Xeon Narcona 3.6Ghz 64-bit cpu's, which do not support prefetchW. Actually this instruction is implemented as a NOOP on newer Intel CPU's, it was originally an extension to the amd64 instruction set to allow optimizations on AMD processors. So why do you say that my Xeon CPU cannot handle Windows 8.1, while Windows 8.0 was fine?

Do you feel that windows 8.1 become so backwards that it needs more than 2MB cache, dual 3.6Ghz 64-bit Xeon (with PAE, NX, SSE2), and 8GB RAM, because it lacks the ability to do a NOOP using prefetchW?

Or has Microsoft made a serious error to require prefetchW?


It need to not throw an illegal instruction fault when it hits the PREFETCHW instruction. If the instruction is simply expanded into a noop by the frontend decoder that's okay.
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