You can't install Windows 10 because your processor doesn't support CompareExchange128 October 13th, 2015
CompareExchange128 error, the problem is that while your CPU may support 64Bit code your hardware / motherboard or BIOS may not.
Overview: I decided to install the Windows 10 Insider Preview on an old eMachines desktop computer (AMD Athlon 64 3400+ CPU) that original came with Windows XP 32Bit installed. It was upgraded over the years to include a discreet NVIDIA 7300 GS graphics card, 2GB of memory and a second disk drive (IDE) with XP installed (Image Backup and restore) to a new SATA drive.
So as not to lose my XP installation I disconnect both drives and connected an empty SATA drive, unformatted and had no partitions.
I tried booting from the 64Bit Technical Preview DVD and after the “Press any key to boot from CD ..” message it just sat there with the Windows 10 logo and did not proceed any further.
So thinking the DVD was defective I tried another build, still no luck. So I used the Microsoft Media Creation Tool to create another 64Bit installation DVD (Build 10240) and try again, same results.
Having never tried Windows 7 on this computer I decided to see if I could install the 64 Bit version. Bingo, was able to boot from the installation DVD and start the install process, I choose the Custom option since there was nothing on the drive to upgrade from and a keyless (skipped entering the product key) install.
The results were positive, Windows 7 Professional 64Bit was up and running, with only one driver missing (Multimedia Audio Controller). I checked eMachines and there are no device drivers available for any version of Windows except XP.
Next I inserted the DVD created from the Media Creation Tool and ran setup.exe when prompted.
Windows 10 started installing.
Windows 10 got as far as Checking for and getting important updates but the install never progressed to the next step after restarting.
So I canceled the install and tried again, this time skipping the updates by choosing the ‘Not right now’ option when prompted to ‘Get important updates’.
I clicked on the ‘Next’ button and that is when the install displayed the “You can install Windows 10 because your processor doesn’t support CompareExchange128” message. Only option at this point was to ‘Close’ the install.
The next day I tried again and was able to install the Windows 10 updates but the restart only resulted in the same CompareExchange128 error.
The problem it seems is that while your CPU may support 64Bit code your hardware / motherboard or BIOS may not. There was no BIOS update for my old vintage 2005 eMachines computer so 64Bit versions of Windows 10 are not able to run on this PC.
Take note this issue also effects some Windows 8.0 users who when trying to upgrade to 8.1 receive the same error message. In short they are also reduced to installing a 32Bit version of Windows 8.1 or upgrading their existing 32Bit version of Windows 8.0 to 8.1 with Update 1 if they want to take advantage of the free Windows 10 upgrade offer.
Summary: Apparently early AMD64 processors lacked the CMPXCHG16B instruction, this instruction is absent from 64-bit AMD CPUs with cores prior to revision F. Apparently the CPU in my eMachines desktop was released prior to revision F.
So I tried the 32Bit version of Windows 10 which installed without any problems and in addition there were no missing device drivers. So a “Clean Install” path from XP 32Bit to Windows 10 32bit versions (Home or Pro) is possible.
(Note: Upgrades to Windows 10 from XP or Vista "which would keep your applications and data files", are not supported)
While the computer only had 2GB of memory installed, finding and upgrading to 4GB of 2.5Volt DDR 400 non-ECC memory cost anywhere from $50 to $100 is not worth the cost for a 10 year old PC with a single core processor. There are plenty of 1GB 2.6 Volt memory sticks available, but with a BIOS that does not allow the user to adjust the memory voltage it may not be a good solution for adding more memory. Besides 2GB of memory is acceptable for a 32 bit OS.
If anything moving from a rather slow hard disk drive to a solid state drive (SSD) would provide more performance even for a SATA-I interface. A Samsung 850EVO 250GB is currently on sale for $96.00 at Amazon and a 120GB for only $61.00, both provide support for SATA-I and their Magician Utility provides support for the lack of TRIM (which is a requirement for Solid State Drives) in Windows XP, Windows 10 natively supports TRIM.
Windows 10 Home (Retail version) $120.00 Windows 10 Pro (Retail version) $200.00
My old XP computer’s specifications: Emachines T6412 Windows XP SP3 Key = J8BM6-MXPH6-3R2BY Micro-Star MS-7184 motheboard Phoenix BIOS LTD 6.0 PG 08/19/2005 AMD Athlon 64 3400+ Four 184-pin DDR DIMM sockets Supports dual channel, DDR 333/400 DDR DIMMs Supports 2.5v DDR SDRAM DIMMs PCI-Express (PCI-E x16) slot available for upgrade