HANDS-ON Dortania's OpenCore Legacy Patcher lets you run newer versions of macOS on unsupported Intel Macs. It's handy, but there are a few things to beware of – including macOS Tahoe. OpenCore Legacy Patcher brings Hackintosh techniques to genuine Mac hardware.
It's an inspired hack that helps you to install newer versions of Apple macOS on older Macs for which Apple has dropped support in recent versions of macOS. Its co-author, Mykola Grymalyuk, has a fascinating retrospective on its development. We introduced OCLP a few years ago when it was still quite new.
Our screenshot then showed version 1. 01, but as the project's GitHub page shows, it's now up to version 2. 4.
- It does still have one big drawback, though. At present, the newest macOS it can help with is version 15 "Sequoia," whose release we covered back in 2024.
In 2025, The Register warned that the forthcoming macOS 26 "Tahoe" would be the last version to have any support for x86 Macs. As we confirmed in September, it supports a mere four x86 Macs. This limited Intel support makes it a significant challenge for the OCLP development team, and nearly a year later, the latest OCLP still does not support Tahoe.
As we've mentioned a few times, the main desktop computer at the Irish Sea wing of Vulture Towers is a 27-inch Retina 5K iMac (late 2015). A couple of years ago, we maxed out this machine with a quad-core i7, 32 GB of RAM, a 1 TB NVMe SSD, and an 8 TB hard disk. It also drives a 27-inch Apple Thunderbolt Display.
It's a capable box, but the last supported OS was 2021's macOS 12 "Monterey." As we mentioned last month, this is now too old for the latest Raspberry Pi Imager. It was time.
Getting started with OCLP Alongside OCLP's own documentation, there are several how-to guides out there, such as the iFixit Guide and Greg Gant's 10-step guide. We are not setting out to recreate them, just to point out the stumbling blocks we encountered. Ever since OS X 10.
9 "Mavericks" in 2013, macOS has been a free download. You can get it from Apple's App Store, and the company even has a downloads page to help you find older versions. When you download a version of macOS, what you get is a macOS application, called "Install macOS [Codename]."
Buried inside this is a little command-line app to create a bootable USB key to reinstall a completely blank machine – for instance, if you fit a new empty SSD. You'll need a fairly big, and ideally fast, key. The recommended minimum is 32 GB.
Then you boot off the key and install or upgrade macOS. However, OCLP can also patch a system disk to make it bootable on an unsupported Mac. It will even download various releases of macOS and create the installation USB key for you.
The basic way that OCLP works is by creating a standard macOS installer and adding a model-specific OpenCore configuration that bypasses Apple's firmware checks. It may also apply post-install root patches for unsupported hardware. Intel Macs use EFI firmware, which means a small hidden partition containing the EFI bootloader, called the EFI System Partition, or ESP for short.
OCLP adds a new entry to this, which shows a special "EFI Boot" entry, as shown in the manual. You must use this to start your newly created key. OCLP does not build a generic modified macOS – it creates a model-specific OpenCore configuration for the Mac on which you run it.
There is an option to bypass that and create a custom USB key for a different Mac, but watch out: by default, it creates one for the machine you run it on. For an easier life, you might want to keep a small partition with the last officially supported macOS for your machine – and if you're installing on a blank disk, do that first, before continuing with the process.
Even after it's created a custom USB, you can't boot this the normal way. You must use the custom "EFI Boot" entry it creates. You will probably do a lot of rebooting.
Don't do this process with a wireless keyboard or mouse, even if they're official Apple ones. Plug in plain old wired USB ones. If it's a PC keyboard, make sure that you know which keys are which in Mac terms.
If the instructions say "hold down the Option key," that means Alt; if they say "press Cmd plus [some other key]," that means the Windows key. Our normal Das Keyboard is a USB 3 device, which might be why it doesn't always register when the machine boots, so we needed to use an additional USB 2 as well. To pick custom boot options, press the Option key (Alt) immediately after the power-on chime, and hold it down.
Wait for all the options to appear, and pick EFI Boot, then in the following boot-device picker, choose the installer for your new version. Don't worry: after it's all installed, you don't need to do this every time – only if you change the Startup Disk to an unpatched, supported version, then need to switch back again. Once you've booted your new, customized macOS installer key, you can either do a clean install or upgrade an existing copy of macOS, just like normal.
As a fallback measure, we used Bombich's Carbon Copy Cloner to make a backup copy of our Monterey partition on another drive, just in case. This has been an essential Mac utility for decades, and it has a handy trick up its sleeve. Since 10.
14 Mojave, macOS has defaulted to Apple's proprietary APFS, and since 10. 15 Catalina, it uses a system of container volumes to keep the core OS semi-immutable and safe. For an example, the Eclectic Light Company explains the Sequoia config.
This limits how much a macOS volume can be shrunk, but Carbon Copy Cloner can image a volume onto any destination big enough to hold the data, which is very handy. Post-install gotchas Of all our apps, only one didn't work. A couple of years ago, Broadcom made VMware Fusion freeware, but we couldn't update past Fusion 13.
With Sequoia, we could update to Fusion 26 – but it didn't work. All VMs had a blank black display. No biggie: we have VirtualBox and the very capable UTM, and both work fine.
Originally published at theregister.com
