On one of my old computers I am having the problem of upgrading to windows 8.1 because my computer does not support PAE, NX, and SSE2. How was I able to install Windows 8 in the first place? I heard the original requirements for windows 8.0 were PAE, NX, and SSE2.
Anyone know a bypass for this on a machine already running windows 8?
IMO 8.1 should have been released in the form of a service pack not an entirely new Windows.
How to upgrade from Windows 8 64-bit to Windows 8.1 32-bit:
I found the answer but it took me some time.
Acquire this file: en_windows_8_1_x86_dvd_2707392.iso
If you're not an MSDN subscriber, you can torrent it, but keep in mind sharing copyrighted content is illegal.
Download Virtual CloneDrive and mount the ISO file to a virtual drive.
Copy the entire contents of the drive to a new folder. Add the ei.cfg file to install windows without a product key.
[EditionID]
[Channel]
Retail
[VL]
0
Use ImgBurn to make your new folder into an ISO file.
Create a Windows 8 bootable USB key and boot from the device.
Install Windows 8.1 without a product key. Select the version of Windows you bought (Windows 8 or Windows 8 Pro).
After installation you can activate Windows 8.1 32-bit with your legit OEM product key.
Note: This is what I had to do to install the 32-bit version since my processor does not support PrefetchW and LAHF/SAHF. When I bought Windows 8, it did not come with a 32-bit CD, hence step 1. My product key did not work until after Windows 8.1 was installed, hence step 2-4.
You can't reliably circumvent them unless you manage to at least obtain the source code for all of Windows and recompile it. (And even then I have some doubts.)
If a program requires SSE2 or something like that, it is generally because it was compiled to use SSE2 instructions – in which case bypassing the requirement checks would mean the program would crash as soon as it reached a place where those instructions were used, because your CPU didn't recognize them. (Having that happen for the OS itself wouldn't be nice, would it?).
Sometimes Windows has code for CPUs both with some feature and without, and detects the supported features at boot time – but I doubt it would bother doing that for something that was listed as required in the first place.
Windows 8.1 requires 3 new CPU features that Windows 8 doesn't require:
To install a 64-bit OS on a 64-bit PC, your processor needs to support CMPXCHG16b, PrefetchW, and LAHF/SAHF
http://windows.microsoft.com/en-gb/windows-8/system-requirements
What is your CPU and how old is it? Windows 8 also requires PAE, NX, and SSE2, not only 8.1, look at @magicandre1981's link above. If your PC is running Windows 8 then it already supports these features
If you want to run Windows 8 on your PC, here's what it takes:
- Processor: 1 gigahertz (GHz) or faster with support for PAE, NX, and SSE2 (more info)
CMPXCHG16b, PrefetchW, and LAHF/SAHF are only required for 64-bit Windows 8. You can still install 32-bit Windows 8.1
For unsupported instructions one can write a patch to trap illegal exceptions and then process in software but it would reduce performance dramatically
I have done many attempts to install Windows 8 RTM in a Pentium 4. None succeeded. The only versions that can be installed are Windows 8 Developer Preview and Windows 8 Consumer Preview. But then forget all upgrades and anything Microsoft (such as IE 11). You can do it for experiment, but not for everyday use. Forget Windows 8 RTM and of course 8.1
I hope that will save you time trying in vain...
To sum up the information scattered in the links in the comments.
All Windows 8 versions officially require PAE, SSE2 and NX. Starting from 8.1 though, you also need CMPXCHG16b and LAHF/SAHF (and PrefetchW, but that's kind of a red herring) for the 64-bit version. In this sense, switching to 32-bit W8.1 is one way to keep up with updates (ironic that some 64-bit cpus would have to give up to it in order to work).
But there are actually hacks to remove this requirement. See W8CPUFeaturePatch or PatchPAE.
