I installed ancient macOS (2014) natively on a 2017 Macbook Air - by maggie

i only did it cuz i could

What do you mean? Isn't that usually a pretty simple process?

No, never. Similar to how it works elsewhere, you usually can't install an older version of any kind on any device.

Mostly, that's because of device support, like GPU drivers and similar. Usually you can brute force it, at the very least. Macs though, are quite a bit different in a couple key ways, making this process very difficult

Why can't you force it?

macOS installers tend to have an explicit list of machines that they can install to. Modifying that list can be a difficult process with a full installer as the list is very deep in the filesystem and you cannot modify it very easily without breaking something.

Additionally, the kernel itself is older than the hardware that I'm using, for example, macOS 10.9, the version I will be installing, is older than both my CPU and GPU. This isn't very specific to macOS though.

How is this possible then? How'd you even get to this?

While playing around with my laptop, I thought of if it would be possible to run a version of macOS that's from before they changed the design to be flat.

I did some slight research and assumed this would be a dead end considering that 10.9 never even supported Broadwell in the first place.

That was before I found a custom kernel for hackintoshing, somone very long ago made a custom kernel for Bay Trail and Broadwell CPUs that coincidentally supported 10.9. I thought it would be worth a shot.

I did manage to boot into an online recovery image, which pulls the OS from Apple directly. The problem in that is, that Apple isn't that stupid to believe the edits to the installable devices I had made, meaning that it saw right through my blatant attempts to fool it.

That felt like an accomplishment, cuz from my previous hackintoshing experience I knew that if you get to the recovery environment you're practically golden and guaranteed that it will in fact work. Right after doing that I went ahead and looked for a full offline installer, which is surprisingly difficult to find, because this is the only version that they didn't publish one for. This felt like some sort of weird cosmic humor to me at that point, but I did find one on the shadiest site in the world.

Anna is looking for romance 25km away!

Sorry, that was the virus I contracted using my keyboard to spread a message. Unfunny jokes aside, it seems to have been clean, and I went ahead to edit the list of supported devices and replace the kernel, except... the full offline installer has a completely different structure I can't edit at all.

Entire two hours of brainstorming filled with failed attempts pass, and I eventually settle for using a VM to install it directly to the drive I wanted to use.

Slightly off topic, but getting a VM in VMWare Fusion to see your entire drive is HELL. You need to make your own .vmdk file for this, it looks like this:

# Disk DescriptorFile
version=1
encoding="UTF-8"
CID=8e4908d0
parentCID=ffffffff
createType="fullDevice"

# Extent description
RW 468862128 FLAT "/dev/disk3" 0

# The Disk Data Base 
#DDB

ddb.adapterType = "sata"
ddb.geometry.biosCylinders = "29185"
ddb.geometry.biosHeads = "255"
ddb.geometry.biosSectors = "63"
ddb.geometry.cylinders = "29185"
ddb.geometry.heads = "255"
ddb.geometry.sectors = "63"
ddb.longContentID = "8f39117d2f188f1d227fbfc88e4908d0"

Okay, what the hell is this?

I have no idea i just copied it from somewhere lol.

The tough part was figuring out the byte amount of the disk and setting the cylinders accordingly, which FYI is done by calculating the block size divided by 256 multiplied by 63, so 468862128/(255x63).

Then all you need to do is import the file, the installer and get installing.

Making sure this works properly on real hardware

Obviously, installing this in a VM might look like cheating, but there are still a few things you need to do to make this work on a real Mac.

1. Installing the kernel

Without installing this kernel, the system will immmediately die when you attempt to boot it after installing, dropping itself into a panic state

2. Editing the hardware compatibility list

Without this step, the bootloader will immediately return a prohibited "nuh uh" symbol, which is less than favorable, probably.

Done!

Ideally, once you do all that, you'll be dropped right into the first time setup. Your keyboard won't work, your touchpad won't work, but everything else will, which is admittedly kinda boring and lame but it's still interesting

To outline how insane this is, this laptop came with Mojave preinstalled, and I'm pretty sure the oldest it can do is High Sierra. The fact that you can even boot something that's 5 versions behind the earliest official version is incredible.

What can you do with this?

I don't know, I think it just looks cool, also, apparently you can write blog posts on it, like this exact one, so i guess that's something you can do

This post was dedicated to all kitty kitty cat cats out there, bai bai!!!

(oh, and i guess i can show a real photo of it running, cuz i think it looks awesome)