How to install amd64 in a 64bit CPU with 32bit EFI


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Jul 14, 2020
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I have a Mac Mini mid 2007 with Debian 10 32 bit running just fine... but there is almost nothing to really work on it... 32 bit, despite my efforts, it's a dead architecture. So it's just to install a 64 OS or upgrade this one right? Well... This Mac Mini got no optical drive (I will try tu put one but is not guarantee it will work), so I have to boot from USB. I have tried a lot of different OSs with both architectures and the systems that will boot are:
  • Mac OS X Lion - works badly, will flood memory and stops in couple hours, besides, it's abandoned by Apple and everyone. But I keep it in a small partition, just in case.
  • Windows 7 32 bits - works good, but it's abandoned by Microsoft. Not reliable, not using right now. It's half abandoned by the market.
  • Debian 10 32 bits - works nice! It's almost totally abandoned by the market.
As I researched and discussed around the web, I have some paths to follow:
  • Upgrade this Debian to 64 bits - but there is low documentation about, not sure if this one will work due to the age:, Many people doubt will work 100% or if will even work.
  • Try to make a custom bootable USB stick - no documentation for Debian, only for Ubuntu. But the start point is Ubuntu 32 bits that is not recognized either. There is a claim that is possible, but the optical media will be required. There is an old article in Ubuntu site and this one: Medium Article
  • Try to install in a new partition using this installation - not sure if it possible, I might try to make a clone of this partition to try some experiments and not lose the only OS is working right here.
Any ideas?

Quite a find! Thanks, arochester, as I will email the referred page to a Mac-using friend of mine!
O.K., so the mid 2007 Mac mini had a Core 2 Duo 64 bit processor, which is the only way a 64 bit OS will run. Learn something every day, as I thought the Mac mini from that era only ran 32 bit :cool:
O.K., so the mid 2007 Mac mini had a Core 2 Duo 64 bit processor, which is the only way a 64 bit OS will run. Learn something every day, as I thought the Mac mini from that era only ran 32 bit :cool:
In fact 64 bits OS won't run officially. I don't know why Apple did like this, but I suppose their wish was to make more with the little box. But the Intel GPU is really above expectations, plus the box was sell with 256MB RAM that barely could run Leopard, and the 5200 HDD was really slow. They did Snow Leopard that was one of the best OS ever that could make the box a real working tool, but the market was not interested in the hardware, almost no game will run. Than Lion came heavy and full of glitches, and than the hacks begin, not only Windows by bootcamp, but Linux, and changes in the poor hardware, more memory (than officially supported) and a SSD. But with Lion being such bad OS and newer OSs pure 64 bit not officially supporting the mini, it was over. I can say the box payed for itself during ten years I used it heavily, but now I am interested in to make work these old machines because I won't see they been drop it in the top of the huge pile of garbage we are creating in this planet. Being honest, a Mac Mini with 4GM RAM and 64 Bit OS is all most of people need to daily work, right?
I tried those instructions. First I tried with Ubuntu, no luck. Maybe worked with version 14, I tried using Lubuntu 19 and 16 LTS. Than I realize I was already in the middle of the process with Debian, but got no luck yet. But it's kinda interesting, I am learning a bit about boot. Also my boot is a mess because of some trash of hybrid partition schema, I will have to fix it. Won't be easy, I will use boot-repair (don't know anything else) and it's complicated to install it because a lot of dependencies, I will create a live Debian 32 just for that - and save it for future need.

Let's move on!
Just giving a feedback of the sate of things. I can't work all the time on this, have just some portion of the day, besides, my mind got stressed sometimes.
The point now is not what to do, but how to do. I am learning about boot and how Grub works. However, my PCs are not ready for the task, there is always something missing, this will make it difficult, if not impossible.
My next goal is to make a bootable ISO for BIOS booting to avoid some EFI limitations of the Mac Mini. I will try to pick the boot part of a Debian 32 bit install and mix it with an amd64 install, making the proper modification in grub.cfg so it will call the 64 bit stuff. I am now looking for the proper tools for that, the first boot code must be in the sector 0 etc... hope to have some news next week...

Let's rock!
Wow! There is a lot of good stuff there, @theoak2, and updated! I am looking at now. After a quick read, I realize I got close to achieve a successful installation of a 64 bit Linux OS, real close! But I got no background enough for that, as Apollo 13 mission, close and far away looks the same. Before I start to try those ISOs and solutions, I will make some considerations that might be useful for others reading this thread and needing info:
  • As long USB solutions are much better in several aspects, old firmware was made for "CD-ROM dependent" hardware, the case of those Mac minis. I decided to put a superdrive no my own. Besides, a 120GB SSD is enough for most cases today, so the couple SSD + superdrive might be a good idea for your old hardware. Besides, a burned DVD is still better as installer media than USB that can be easily lost, formatted accidentally or sucked by the vacuum cleaner :mad:
  • There is a GPT - MBR issue with Mac minis that is not mentioned by Linux distros websites. I could only work in MBR as long you will see a lot of people advising to work in GPT. There is also the hybrid GPT/MBR solution for Windows trough Botcamp and dual boot. I had once Debian, Mac OS X and Windows in this way, but there is low info about it. I can only say that the old fashioned MBR is what is working for this purposes now.
  • Which one to pick? There is a lot of Linux distros and still the mod macOS. Yes, Mojave will still work. I haven't experienced yet, but I bet the old CPU will struggle to run Mojave. I know there is the Olaria distro and also the payed Osafo option. Don't even try Catalina, Mojave is better, as Snow Leopard was much better than Lion for the Mac mini. As for Linux distros, I don't have knowledge enough to say for sure, but as long Ubuntu is very popular and always mentioned as reference, Debian is better. I confess I am kinda sick of Ubuntu (and flavors) problems, they are not few and some are critical, not easy to solve, Terminal all the time and so on. Finally, as long they say Ubuntu is good for the Macs, they drop official distro in 14, there is no update from 14 to 16 and above, so forget about Ubuntu support for Macs.
  • Worth to mention here some new boot load installers as YUMI he mentioned: I tried Multibootusb, Sardu and Ventoy. This last one is simple but have worked good, will install a visual multiboot with some tools etc.. Sardu got a payed pro version and support. There is a lot of live resources, as long many people will say those hardwares are dead.
I have not tried making USB with those ISOs made with isomacprog, but it should work. My Mac Mini 2007 has working combo drive. Also I have external DVD drive that seems to work with everything. So may be worth getting external DVD drive.

You can also use another computer to install to a hard drive or SSD, then move that drive to Mac Mini if you are comfortable with disassembling computers.
My Mac mini is 2007 too. It's combodrive was destroyed by an unbalanced CD a long time ago, I replaced by a superdrive from an iBook, it is not perfectly installed inside, but it works. External USB drives or even Sata external with IDE interface won't boot. I think I already tried external installation and did't work, but at that time I was using two drives (SSD + HDD) so I can't say it won't work. What I can say and you probably know Apple killed this product, don't know exactly why, maybe they regret about 32/64 bits strategy that demands specific solutions and support.

- Don't worry my Mini, daddy will save you!!!
So... it works! I tried Mint 20 and it worked at the first try, that was easy!

I advise people to read what is there, a lot of interesting stuff.

As always, there is a BUT - a big one. Linux won't see beyond 3GB of RAM memory. I don't know how Linux map memory at boot, but it will probably rely on EFI. Maybe there is a way to overcome this, I don't know... yet...

Right now, I will enjoy this awesome distribution!
Backup first and then try:

sudo apt-get install linux-restricted-modules-server linux-headers-server linux-image-server linux-server

And then reboot. You still can't use more than 3 GB per process, but your system should see the full amount of RAM and other processes can use the rest of the RAM. You can also try to add PAE support in other ways, but the above should work (on Mint) and be pretty painless.
I did execute the command and reboot. I can't see any changes, just "feel" a very quickly OS considering the age of the machine. Is there a way to check if OS is really using the 1GB of hidden memory?
It seems to me PAE is a technology for 32bits OS, so the memory above 3GB will be used somehow even not in continous way - correct me if I'm wrong...
Does the machine report more than 3 GB now? Try 'free -m' and see what that says.

And, I know it *should* work. You can probably load up some applications, run top (I prefer htop but that's a story for another day) and then do the math.
The answer is 2960MB of total memory available, must be the 3GB less the video memory. Also the swap is not used unless I do open a lot of apps, maybe there is 4GB being used but the diagnose tools are missing... Thought we need more powerful tools, but as newbe I don't know any. For Mac there is Onix that is very complete, but also some other small ones specialized that "knocks at the door" of each device to get the real information. Sometimes, a bootable USB is needed to further investigations.

In the Mac OSX 32 bits occours the opposite, the system information tools reports 4GB of RAM, even the OS native, but we know it is not real, and we can only see in System Monitor or with those specialist apps.
Now that I think of it, I've never encountered this in real life. I mean, I know the fix - the fix is to enable PAE somehow. We did that by making it a server in part. So, I know it works - but I don't *know* it from firsthand experience. I've used 64 bit CPUs since they first became regularly available (more or less). I even used a 64 bit version of Windows XP back in the day.

You can use giant gobs of memory with 'config_highmem' enabled on 32 bit Linux - something like 32 GB of RAM can be used that way. I *know* this, but I don't *know* this from personal experience. So, I have no idea how to see that the RAM is being seen/utilized. I tried doing some searching, but nothing popped up that I noticed. But, I do know that so long as your CPU supports PAE (a large, large percentage of them do - especially as you get closer to modernity) and the kernel supports it, then the Linux kernel will address more than 3.5 GB of physical memory. I've just never, ever had to test this.

That's a pretty good question. Ain't gotta clue.
A Linux distro that was thoughtful enough to build in support for this aging yet great hardware!!

I have a mid-2007 mac mini A1176 1.83 C2D with 4GB RAM. The new Zorin 16 Core and Zorin 16 Lite run almost out-of the box in GPT/EFI mode. The installer has EFI/Grub 32 bit support built in as well as 64 bit. You can use Etcher or Start-up Disk Creator but both the USB stick and the internal hard drive (if changed) but be formatted in GPT/FAT32.
the Mac mini from that era only ran 32 bit
it was not unusual around that time for manufactures to install a core 2 64 bit processor on a 32 bit motherboard [I have had several over my bench ] a few could by upgraded by swapping out the 32 bit Bios chip but most would have a full 32 bit MB these will only ever run 32 bit systems, although Mac/Microsoft/ now only provide 64 bit and it is being dropped by Ubuntu there are several Debian based 32 bit distributions you can use

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