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Why would you want to have no bootscreen? Take a look at the OpenCore wiki post which shows how to get the bootscreen with OpenCore and you will also see the sectio which tells you how to install Windows 10 for UEFI booting.
 
Why would you want to have no bootscreen? Take a look at the OpenCore wiki post which shows how to get the bootscreen with OpenCore and you will also see the sectio which tells you how to install Windows 10 for UEFI booting.

I plan to get my Pulse RX 580 8 gig flashed by macVidCards sooner or later but for now I'll have to deal with no bootscreen. At the same time I want Windows 10 on my Mac
 
I plan to get my Pulse RX 580 8 gig flashed by macVidCards sooner or later but for now I'll have to deal with no bootscreen. At the same time I want Windows 10 on my Mac

OpenCore can give you the boot screen without having to get the RX 580 card flashed. I use an RX 580 and can run Catalina by using OpenCore’s OpenCanopy graphical interface as an alternative to the OpenCore boot picker menu. Also early testing of Big Sur betas using OpenCore suggests OpenCore makes it possible for the MacPro 5,1 use to Big Sur.

The method of installing Windows you are asking about from that website is a nicely formatted write up of a method that was developed by one of the posters on the OpenCore thread, h9826790, as far as I know he now uses OpenCore for booting his operating systems. Why not ask him directly on the OpenCore thread directly what he suggests now. The OpenCore method of booting Windows installs Windows using UEFI. Some Windows 10 installation methods will ruin your NVRAM by overwriting with excessive security certificates which can make your MacPro unbootable.
 
OpenCore can give you the boot screen without having to get the RX 580 card flashed. I use an RX 580 and can run Catalina by using OpenCore’s OpenCanopy graphical interface as an alternative to the OpenCore boot picker menu. Also early testing of Big Sur betas using OpenCore suggests OpenCore makes it possible for the MacPro 5,1 use to Big Sur.

The method of installing Windows you are asking about from that website is a nicely formatted write up of a method that was developed by one of the posters on the OpenCore thread, h9826790, as far as I know he now uses OpenCore for booting his operating systems. Why not ask him directly on the OpenCore thread directly what he suggests now. The OpenCore method of booting Windows installs Windows using UEFI. Some Windows 10 installation methods will ruin your NVRAM by overwriting with excessive security certificates which can make your MacPro unbootable.

Aren't there caveats to OpenCore? I've read that some of the USB ports on the cMP stop working
 
Aren't there caveats to OpenCore? I've read that some of the USB ports on the cMP stop working

All my USB ports work I have never read on the OC MacRumors thread of issues with USB ports for the versions I have used, 0.5.8, 0.5.9, 0.6.0 beta. I cannot speak for earlier versions. People are now working out booting Big Sur. The only caveat I have is that I did not learn about OC earlier.

It takes a bit of reading to familiarize yourself with the terminology and procedures involved in setting up OC. However the first post of the open core thread is a wiki post and it has a well written and well documented cookbook approach to getting the BASIC boot menu of OC up and running. The forum members are very knowledgeable and helpful. There is a separate wiki instructional for using OC with Windows 10. OC works for both hackintoshes and Macs, perhaps what you read about USB ports pertained to hackintoshes or earlier versions of OC. OC is a path forward at least through Catalina for the cMP. Promising right now for Big Sur too.

OC gives you the ability to boot to a bootpicker menu or the OpenCanopy graphical interface without modifying your video card.

As OC is all software if you find it doesn’t work for you, you could always go back to your earlier method or flashing your video card.
 
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Here's what I did, and as I type this I am on the "windows" side of my mac. I feel kind of dirty. I downloaded Windows 10 and put it on a dual layer DVD because it takes up greater than 4.7 Gb. Then I took out every hard drive except for one, and I started the computer from the CD drive by pressing the option key. I had to do the custom install to erase the formatting of my SSD drive and then it "magically" booted up. I'm still at a loss that that it actually worked. Both my wireless keyboard and my internal WIFI work pretty much perfect, the only difference is that I lost my keypads, but I guess they can be mapped. Still in a state of disbelief that this even worked.

Now back in Mojave Dark mode. ahhh... it took a while to get back to Mac. I had to install boot camp on the windows side and I didn't exactly follow the instructions well of making it a usb drive. I just installed it on the windows drive and it "worked". I downloaded the Mac updates on the windows side and as well and got my keyboard number pads back.

It was REALLY stubborn about letting me boot into my Mac OS, in fact I had to take my hard drive out and with my usb to sata adaptor and I asked it again to start from Mac OS. It worked I can't say why but it did work, but it's late and I'm not up for going over to Windows until I have time away from work.

Still have boot screen on Mac.
 
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Aren't there caveats to OpenCore? I've read that some of the USB ports on the cMP stop working
This a an old post now, but still better to let the others know that no such thing exist. May be you messed up some Hackintosh issue with cMP.

There is a 15 ports limit on Hackintosh, therefore, Hackintosh user should do a port mapping (e.g. via SSDT in OpenCore) to disable some ports, and makes the total USB ports count no more than 15.

But there is no such problem on a genuine Mac.

So far, OpenCore only add new functions (e.g. UEFI GOP boot screen, HEVC hardware encoding, ability to run Big Sur, etc) to cMP, but not stopping any existing hardware / software to function properly.
 
Hi, i want to flash my 580 (which seems to have some strange rom). Therefore I installed win10 on an usb-disc (which took me 1 day to figure out the exact way....) However, I was able to install win on that usb and boot into it and do the complete configuration until showing up the win desktop etc. Everything seems fine, so I shut down the computer. Now when I power it up and want to boot into win, it either powers of again after some seconds of blue screen or it sends me to repair-mode. Does anyone has experience with this problem? I really don't know hat to do anymore... thanks
 
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