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I'm having Intel(R) Pentium(R) 4 CPU 3.00GHz Processor with 2GB RAM. While trying to install Windows 8.1 Pro 64-Bit i gave me an error saying that the processor is not compatible with Windows 8.1 Pro 64-Bit .I checked the system requirements and found that my processor doesn't support PrefetchW but all the other requirements are supported.

HTT * Hyperthreading enabled

X64 * Supports 64-bit mode

NX * Supports no-execute page protection

PAE * Supports > 32-bit physical addresses

SSE2 * Supports Streaming SIMD Extensions 2

CX16 * Supports CMPXCHG16B instruction

PREFETCHW - Supports PREFETCHW instruction

Note : '*' means it's there(supports) and '-' means it's not there(doesn't support)

I know i'm asking a poor question. But i want my old processor to run Windows 8.1 64Bit anyway. Is there any way to run Windows 8.1 64 bit without PrefetchW support?

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  • You could try to disable superfetch/prefetch ==> tomshardware.com/reviews/ssd-performance-tweak,2911-5.html
    – whs
    May 1 '15 at 2:12
  • @whs My processor does not support prefetchw
    – CodeIt
    May 1 '15 at 3:28
  • I know. That's why I suggested to set it off in the OS. However, I am not sure whether it will let you install the OS in the first place.
    – whs
    May 1 '15 at 3:59
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    If it is an option superuser.com/questions/831394/… looking at the web the 3 items PrefetchW & LAHF/SAHF & CMPXCHG16B effects the 64bit OS versions. From what i can tell so far, the 32bit OSes do not have that problem.
    – Psycogeek
    May 1 '15 at 4:23
  • @whs I'll try and will give an update.
    – CodeIt
    May 1 '15 at 5:05
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no, this is not possible. The only way to install Windows 8.1 on this CPU is to use the 32Bit (x86) Version which is recommend when only using 2GB of RAM.

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    for a reference for anybody wondering how things work on later CPUs without that capability - superuser.com/questions/931742/… Jan 22 '18 at 21:23
  • Removing prefetchw instructions from an executable is a very easy modification. They can all be replaced with NOP instructions. Then you just have to bypass the Windows installer check, and Windows File Protection, and then make sure update files are modified too. There was talk of a patch back when 8.1 came out but I'm not sure of the current status of it. Dec 1 '20 at 16:49

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