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Solve : What is PrefetchW ??

Answer» <html><body><p>I went to install Windows 8.1 trial and it asked me if I wanted to check for dow2nloads. I said yes, it took awhile, then it said:<br/>Quote</p><blockquote>You can't install Windows 8.1 because your processor doesn't support PrefetchW.<br/></blockquote> What? Never here of it. It is a CPU instruction.Quote from: BC_Programmer on August 15, 2014, 03:40:09 PM<blockquote>It is a CPU instruction.<br/></blockquote><br/>Not available on certain old CPUs, e.g. some Pentium 4s, Celerons etc. Your CPU does not support Windows 8.1.<br/><br/><a href="https://answers.microsoft.com/en-us/windows/forum/windows_8-windows_update/cannot-upgrade-to-windows-81-because-of-prefetchw/d5106cb9-eb0a-48df-9922-409e693a993b">http://answers.microsoft.com/en-us/windows/forum/windows_8-windows_update/cannot-upgrade-to-windows-81-because-of-prefetchw/d5106cb9-eb0a-48df-9922-409e693a993b</a><br/>For 64 bit installations of Windows 8.1 the CPU must support CMPXCHG16b, PrefetchW and LAHF/SAHF instructions. PrefetchW is an AMD 3DNow! instruction and Intel desktop processors became <a href="https://interviewquestions.tuteehub.com/tag/compatible-409678" style="font-weight:bold;" target="_blank" title="Click to know more about COMPATIBLE">COMPATIBLE</a> from family 15/model 6/stepping 1 (Cedar Mill, the 65 nM final revision of the Pentium 4 released on January 5, 2006) thus I should think all 90 nM Pentium 4 era CPUs and earlier are incompatible (Prescott and earlier). <br/>Geek, on your <a href="https://interviewquestions.tuteehub.com/tag/profile-25809" style="font-weight:bold;" target="_blank" title="Click to know more about PROFILE">PROFILE</a> your listed machines use the following CPUs:<br/><br/>Dell E1705 cpu: Intel Core Duo T2500<br/>Dell GX520 cpu: Intel Pentium 4 <br/><br/>Which machine are you talking about? If it is the Optiplex GX520 desktop, that uses a Prescott era Pentium 4 and would not be Windows 8.1 compatible.<br/><br/><br/><br/>Dell GX520 CPU Intel Pentium 4 <br/>I was trying a 64 bit Windows 8.1<br/><br/>Strange, I had to replace that CPU because the chip set did not fully support the new CPU in that group. After that I tried to install Windows 8.1 and is stalled opr gave the error message.<br/><br/>The machine runs Windows 7 64 bit with not problem.<br/><br/>Anyway, I am not <a href="https://interviewquestions.tuteehub.com/tag/going-1008806" style="font-weight:bold;" target="_blank" title="Click to know more about GOING">GOING</a> to rip it open and swap the CPU again. <a href="https://interviewquestions.tuteehub.com/tag/instead-248606" style="font-weight:bold;" target="_blank" title="Click to know more about INSTEAD">INSTEAD</a>, I have Windows 8.1 now on a Dell 755 machine and it works.<br/><br/><br/><br/>Your an adventerous guy Geek...<br/>Quote from: patio on August 16, 2014, 05:12:44 PM<blockquote>Your an adventerous guy Geek...<br/></blockquote>For some reason Windows 7 64 does not seem to care about a missing code. But it seems to matter to Windows 8.1 and I can not run it on that machine.<br/><br/>Thanks to Salmon Trout for the research. So did Intel have t o buy a bunch of <strong>PrefetchW</strong> jelly bean bits from AMD? <br/><em>This may one of the things science will never understand</em>. OK, some looking around shows this issue is well known. Some Intell Pentium CPU chips just don't have it. Hard to accept! <br/>Look at this:<br/><a href="https://answers.microsoft.com/en-us/windows/forum/windows8_1-windows_install/windows-81-64bit-update-not-compatible/d0a08d02-4f17-4581-8f39-3d71fc737eb8">OK for Windows 8, but not 8.1</a><br/>Quote<blockquote> The CPU must also support the following<br/>LAHF-SAHF * Supports LAHF/SAHF instructions in 64-bit mode<br/>CX16 * Supports CMPXCHG16B instruction<br/>PREFETCHW * Supports PREFETCHW instruction<br/>The Intel Pentium D 820 does NOT support the last one :-( so it seems that I'm stuck on 8.0<br/></blockquote>Not likely MS will continue to support Windows 8.0 just for a few.<br/>This may mean that a few people with the wrong CPU have to get both a new motherboard and a CPU if the chip set does not support the newer CPU. <em>Thanks a lot, Intel!</em>Quote from: Geek-9pm on August 16, 2014, 11:15:40 PM<blockquote>This may mean that a few people with the wrong CPU have to get both a new motherboard and a CPU if the chip set does not support the newer CPU. <em>Thanks a lot, Intel!</em><br/></blockquote><br/>I think you just have to suck it up; why should Microsoft hold back OS development to cater for people with hardware that is fit for the dumpster?<br/>Quote from: Salmon Trout on August 17, 2014, 12:02:54 AM<blockquote>I think you just have to suck it up; why should Microsoft hold back OS development to cater for people with hardware that is fit for the dumpster?<br/></blockquote><br/>Bah Humbug! Why, this new "386 enhanced mode" is just a ploy by Intel I tell you!I see I miswrote the <a href="https://interviewquestions.tuteehub.com/tag/unit-240206" style="font-weight:bold;" target="_blank" title="Click to know more about UNIT">UNIT</a> for nanometres: the SI symbol is nm - small n small m<br/><br/>Quote from: Geek-9pm on August 16, 2014, 11:15:40 PM<blockquote>OK, some looking around shows this issue is well known.</blockquote><br/>Why didn't you do that before starting this thread?<br/>Quote from: Salmon Trout on August 17, 2014, 04:16:24 AM<blockquote>Why didn't you do that before starting this thread?<br/></blockquote>Because I had never heard of it and did not know it was a problem. I just could not believe there was anything missing on my Pentium D dual core 64 bit Intel CPU. It is not like I was running an old Pentium that was missing part of the math math tables years ago. I thought that by now Intel would have it all over with.<br/><br/>As was said in the thread, it is an instruction introduced by AMD. It is part of the 3D set.<br/><a href="https://en.wikipedia.org/wiki/3DNow">http://en.wikipedia.org/wiki/3DNow</a>!<br/>Quote<blockquote>3DNow performance-enhancement instructions<br/> FEMMS – Faster entry/exit of the MMX or floating-point state<br/> PREFETCH/PREFETCHW – Prefetch at least a 32-byte line into L1 data cache (this is the non-deprecated instruction<br/></blockquote><br/>I am glad I asked. The info from Salmon Trout and others helped me understand. I am a slow learner an d I value the help of forum members. Besides, It is fun to come here. <br/>Quote from: Geek-9pm on August 17, 2014, 02:03:50 PM<blockquote>It is fun to come here. <br/></blockquote><br/>A fair comment!<br/><br/></body></html>


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