Can I Use Windows XP x86 on my Prospective Custom PC?

Here is what has not been answered about your questions and I feel like Ken Blake may not know all the answers to your questions.

The CPU - Intel Core i7 4790K is a Haswell.

Intel decided not to provide AHCI Windows XP drivers for Haswell and later CPUs.

The only way you can install XP and avoid the dreaded

0x0000007B BSOD error

You will need the proper Intel AHCI driver for Windows XP installed either via a USB floppy drive with the F6 option or slipstreamed using nLite.  However you might be able to change in your BIOS to legacy IDE Mode emulation to avoid needing to install the proper Intel AHCI driver that most SATA hard drives now use.  SATA hard drives were not fully supported at the time XP came out as IDE was the standard then.  I was curious in your case since it has been 8 month I will assume you purchased the Haswell CPU.  Did you try the IDE legacy emulation method instead of AHCI to complete the XP installation on your Haswell 4670K CPU?

The other issues faced would be needing a discrete graphics card that has XP 32-bit driver support as no Intel integrated graphics driver has written XP 32-bit drivers for Haswell CPUs which is why I recommend not going to Haswell CPU and getting an Ivy Bridge-E based 2011 Enthusiast CPU as the cut off point for a CPU.  Investing in Haswell will give you more headaches if you wish to maintain XP compatibility and should be avoided.  This is not the fault of the technology but Intel for not wanting to support XP any further and abandoning create drivers in order to force people to upgrade to a newer OS.  This also coincides with Microsoft dropping support for XP after April 8th, 2014.  However, in my opinion Intel should have followed through and created XP AHCI drivers for their Haswell processor and their Intel integrated graphics.

What kind of Sound Card do you have installed since you mentioned you are using XP software for MIDI support?  What kind of sound software are you using MIDI with?  I am into sound design as well and the built in Microsoft GS Wavetable SW Synth I agree sounds horrible.  Which 3rd party ones are you using?

As for memory limits.  Theoretically Windows XP 32-bit can use up to 3.3GB of memory and not 4GB so that leaves about 700KB wasted.

To be exact on my Windows Task Manager the value is 3,343,804 KB = 3,424,055,296 bytes.

However I found a way to bypass this limitation and use 32GB of memory installed (4 x 8GB) DDR3 memory modules under XP instead of it just sitting idly wasted.

I created a RAMDISK using the Invisible Memory range outside the reach of standard Windows XP of 29428KB or 30,857,461,760 bytes = 28.7GB in size.

Currently I use this as a temporary download folder for files, browser cache, installing or decompressing files without wearing down my hard drive or SSD.  It's really remarkable how fast XP is when using a RAMDISK with it.  If you go with a socket 2011 motherboard I have seen one that can install 128GB max although finding  (8 x 16GB) DDR3 memory modules can be expensive and I can't see people spending that kind of money except for heavy intensive video processing and most likely will get (8 x 8GB) DDR3 since 64GB is more affordable.  But if you got the money to throw around I would get the 128GB max memory 2011 motherboard and create a 124.7GB RAMDISK.  This would be extremely powerful for video editing.  I would suggest getting the 6-core Ivy Bridge-E Core i7-4930K for best bang for the buck and also exceed 4-cores.

IF this XP SATA AHCI driver limitation can be successfully bypassed using the IDE emulation mode via your BIOS then I would suggest getting the Core i7-5960X Extreme Edition which is a true 8-core CPU.  There is no point in going to 4-core CPU on a 2011 enthusiast motherboard since a 1155 and 1150 easily can install a 4-core CPU so what's the point as you aren't really gaining a whole lot for your money?  Go with the 6-core Ivy Bridge-E for XP support or 8-core Haswell-E for max cores if you are going to a socket 2011 motherboard.

I also do multi-OS booting.

I have successfully done 98SE / XP / Vista / Windows 7 / Windows 8.  Although 98SE cannot work with more than 1GB of memory installed without using a special 3rd party patch you have to buy.

Although I really despise including Windows 8.0 in a multiboot as they introduced a new bootloader and I did it purely to see if it was possible.

Personally I recommend XP Pro SP3 32-bit / Vista SP2 DirectX 11.0 64-bit as my preferred dual boot for 32-bit and 64-bit OS if I was going to do two Windows operating systems.

Vista SP2 with DirectX 11.0 is a much more better interface than Windows 7 Ultimate.  Windows  7 Ultimate really in my opinion is a step back in terms of user interface.  One thing they did that I hated was remove the Quick Launch and classic mode look.  I've seen people write create walk throughs on how to customize it so it is similar but it's still not the same.  The File Search engine is horrendous and slow.  If you are deleting or moving files it always wants to refresh your file list when is aggravating.  XP 32-bit is quick and responsive with its dated interface which in my opinion is still superior to Windows 7 Ultimate.  Stick to Vista SP2 DirectX 11.0 since it still has Quick Launch and has a better search engine though not as good as XP.  Since I'm able to make use of my entire 32GB of RAM or invisible memory above the 3.3GB XP system max there is no point in me needing to use Windows 7 Ultimate and most desktop consumer motherboards max out at 32GB.  However if I need to run any special programs that are only 64-bit based then I would go with Vista SP2 DirectX 11.0.  The only real benefit of choosing Vista SP2 DirectX 11.0 vs Windows 7 Ultimate is support for USB 3.0 speeds and DirectX 11.1 but to be honest at most you'll get four USB 3.0 ports on most motherboards and the rest will be USB 2.0 based.  If you got four dedicated USB 3.0 devices that will make use of such high transfer rate speeds then I suggest dedicating a cheap file server to Windows 7 but not my primary system if you want speed and efficiency and backward compatibility to your XP software.

The only other comment I would make is never use virtualization software to do your XP testing.  It is better to use real XP than run XP under an emulated environment.  The first thing you will notice if you were to run two identical computers side by side is the emulated XP environment is not as fast as running real XP and the second thing is you might not be using the actual video and sound cards under that emulated environment but virtual video and sound cards emulated under that environment.  This might create compatibility problems as a result.  But if your software is not dependent on using your actual video or sound card then you might as well contact the developer to see if they have a 64-bit version of their program and run it on Windows 7 directly.

Try running Windows 98SE programs under Windows XP Virtual PC and you will find you are not using the actual video and sound cards but emulated ones.  When running older games that make use of 3D video cards or 3D audio in the sound card, the emulated video and sound cards will be inferior.

If you were to try running XP software under Windows 7, 8, or higher this program called VirtualBox seems to be free and might be worth testing out.

https://www.virtualbox.org/wiki/End-user\_documentation

I haven't tried it myself since I prefer using the real OS unemulated.  But if you can't get XP to install on a Haswell CPU this is worth a shot.

I hope you can answer my questions as I'm interested in hearing about what has happened since the last 8 months.  :)

OK. Well, thank you for your help. Have a nice remainder of the weekend!

On Sat, 13 Sep 2014 18:52:07 +0000, Michael A. Grumbein wrote:

Thank you for your prompt response about the RAM and CPU, and thank you for that link.

You're welcome. Glad to help.

Running a virtual machine might be a good idea, as long as it can function exactly as the OS would if installed directly on the hard drive.

OK.

As for those hobby activities, I compose music in MIDI format. Later versions of Windows have very limited MIDI abilities, as it is not natively possible to use third-party soundfonts, and they are stuck with what was in XP called Microsoft GS Wavetable Synth, which has very low-quality samples. While it is possible to use third-party virtualized tools to enable soundfont support, MIDI synchronization becomes inconsistent in the newer versions of Windows.

I also like to bet-test many types of software, especially maintenance and optimization tools made by manufacturers who still support Windows XP (e.g., Advanced SystemCare by IObit). I want to be able to provide feedback to these manufacturers regarding how their beta software runs in XP and in 8.1.

OK, understood.

Also, I probably should have chosen a different phrase than 'dual-boot,' as I actually have two hard drives, one which will have Windows XP and one which will have Windows 8.1. I plan to select the boot media at startup. Dual-booting normally refers to installing both OS's on separate partitions on one hard drive, so I felt I should clarify this.

Nom dual-booting refers to selecting which operating system will boot
at startup. Whether they are on two partitions on a single or two
separate drives is irrelevant,

As long as there will be no compatibility problems, as yet I plan still to use my dual-harddisk boot selection configuration, but your suggestion to run a virtual machine is a great one. I have just been a bit wary of virtual machines because I have never used one before and rather than worrying that it might not provide a completely accurate representation of Windows XP for my purposes, especially beta-testing, I would just use hardware and software I already own and keep using XP on the same hard drive as was in my old desktop, even though that would require reactivation or perhaps even reinstallation.

Thank you for your help. You have answered my questions, but I would still like to see your input about my activities and whether it would be preferable to use a virtual machine for them. I'll think about venturing into the unexplored territory (to me) of virtualized operating systems if you can convince me!

No, I won't try to convince you. Especially for the beta testing, it's
probably best to do it your way.

Thank you for your prompt response about the RAM and CPU, and thank you for that link. Running a virtual machine might be a good idea, as long as it can function exactly as the OS would if installed directly on the hard drive.

As for those hobby activities, I compose music in MIDI format. Later versions of Windows have very limited MIDI abilities, as it is not natively possible to use third-party soundfonts, and they are stuck with what was in XP called Microsoft GS Wavetable Synth, which has very low-quality samples. While it is possible to use third-party virtualized tools to enable soundfont support, MIDI synchronization becomes inconsistent in the newer versions of Windows.

I also like to bet-test many types of software, especially maintenance and optimization tools made by manufacturers who still support Windows XP (e.g., Advanced SystemCare by IObit). I want to be able to provide feedback to these manufacturers regarding how their beta software runs in XP and in 8.1.

Also, I probably should have chosen a different phrase than 'dual-boot,' as I actually have two hard drives, one which will have Windows XP and one which will have Windows 8.1. I plan to select the boot media at startup. Dual-booting normally refers to installing both OS's on separate partitions on one hard drive, so I felt I should clarify this.

As long as there will be no compatibility problems, as yet I plan still to use my dual-harddisk boot selection configuration, but your suggestion to run a virtual machine is a great one. I have just been a bit wary of virtual machines because I have never used one before and rather than worrying that it might not provide a completely accurate representation of Windows XP for my purposes, especially beta-testing, I would just use hardware and software I already own and keep using XP on the same hard drive as was in my old desktop, even though that would require reactivation or perhaps even reinstallation.

Thank you for your help. You have answered my questions, but I would still like to see your input about my activities and whether it would be preferable to use a virtual machine for them. I'll think about venturing into the unexplored territory (to me) of virtualized operating systems if you can convince me!