In 2021 I decided to go all-in on a 2013 (trashcan) Mac Pro I saw listed on Craigslist. Some might have considered this to be a “bad move” from the start, but I thought the 2013 Mac Pro was simply the most amazing computer ever made and $950 seemed like a great deal ¹.

Little did I know, the 2013 Mac Pro suffered from severe thermal issues and I soon became one of the thousands of unhappy users experiencing spontaneous freezing and crashes thought to be caused by Apple’s proprietary dual AMD FirePro GPUs.

If I was in the market for a new Mac, the right thing to do would have been to get an M1 Mac mini. Not only are the M1 Macs faster, they are also cheaper and consume significantly less energy. ² However, I wasn’t really in the market for a Mac, what I wanted was a server.

As it turns out, the 2013 Mac Pro is a very compelling server. It is extremely quiet, compact, and rocks a 12-core Intel Xeon E5 with 64GB of ECC memory. Unfortunately, I wasn’t expecting the thermal issues and kernel panics, which made me skeptical of this machine’s viability as a reliable home server, so mostly it sat on a shelf.

Eventually, I decided to see if I could install Linux or maybe even FreeBSD alongside macOS. My hope was that by running on a minimal “headless” environment, I could avoid any stability issues due to the GPUs. Furthermore, I’ve been interested in trying out FreeBSD for a while because of two very compelling features: ZFS and the base system ³.

While ZFS has been available on Linux for several years now, it has always been somewhat of an outcast, with Btrfs being the “modern” flagship filesystem. Meanwhile, FreeBSD has proudly supported ZFS as a first-class filesystem since 2008.

Besides ZFS, I really like the unified deployment model of the FreeBSD base system. This provides a level of consistency and correctness in the operating system that I think the Linux deeply struggles with.

This was going to be my first time installing FreeBSD, so luckily I had my T470 lying around to experiment with. I wasn’t expecting the installation on the Mac Pro to go smoothly, so having a computer that was known to be compatible with FreeBSD was really convenient. I was able to run though several installations to get a sense of how things would go on the Mac.

The very first thing I did was disable disk encryption (FireVault) on the Mac Pro. I’m not sure it would have been a problem, but I didn’t have any issues turning FireVault back on after completing the FreeBSD installation process.

One of the biggest drawbacks to FreeBSD is that there is much less content online to help troubleshoot issues or answer all the random questions you might have. Fortunately, between the FreeBSD, Hackintosh, and Linux communities, I was able to cobble together enough information to get a successful multi-booting environment setup on the Mac Pro.

After testing my bootable FreeBSD USB drive on my ThinkPad, I tried to boot into it from the Mac by holding down the Option (Alt) key during startup.

I was pretty excited after seeing the FreeBSD boot menu show up. I wasn’t sure what to expect because the Xeon E5 doesn’t have integrated graphics and I wasn’t sure the AMD FirePro’s were going to work. Although my enthusiasm didn’t last long, only a few seconds into the boot process and it was game over: The console was endlessly streaming the text pcib8: Power Fault Detected and became completely unresponsive.

Somehow, I was able to dig up an old forum post by someone with this exact issue but unfortunately it went unresolved. However, it gave me hope a solution was out there.

I spent about half an hour playing around in the boot menu trying to figure out if I could get something to work. Single User Mode had the same problem and I wasn’t really sure how to use the Loader prompt. However, I felt like I was making progress.

My biggest clue was the pcib8 bit. Since this was an error message during PCI device initialization, I started searching the web for things like “FreeBSD pci won’t boot” and “FreeBSD power fault detected”.

Once it became clear that I was on my own with this one, I pulled up the FreeBSD manual pages for boot(8), loader(8), and pci(4) and started reading through them. I began to get a sense for how the FreeBSD boot process worked and was ready to try setting custom boot options.

Amazingly, I discovered a single boot option that fixed the issue. Now I could finally get into the FreeBSD installer and live environment!

Here is all I needed to get FreeBSD to boot on the Mac Pro:

1. Press 3 to “Escape to loader prompt”
2. Enter: set hw.pci.enable_pcie_hp="0" to disable PCI-express HotPlug
3. Enter: boot to boot

$ cat /etc/fstab
# Device        Mountpoint      FStype  Options Dump    Pass#
/dev/gpt/rootfs /               ufs     rw      1       1
/dev/gpt/swapfs none            swap    sw      0       0
#/dev/ada0p1    /boot/efi       msdosfs rw      2       2

diff -u original/asmc.c my-patch/asmc.c
--- original/asmc.c     2021-12-28 23:43:20.905442244 -0600
+++ my-patch/asmc.c     2021-12-29 00:10:38.424770226 -0600
@@ -328,6 +328,15 @@
     ASMC_MP5_TEMPS, ASMC_MP5_TEMPNAMES, ASMC_MP5_TEMPDESCS
   },

+       /* Idem for the Mac Pro 2013 (cylinder) */
+       {
+    "MacPro6,1", "Apple SMC Mac Pro (2013)",
+    ASMC_SMS_FUNCS_DISABLED,
+    ASMC_FAN_FUNCS2,
+    ASMC_LIGHT_FUNCS_DISABLED,
+    ASMC_MP6_TEMPS, ASMC_MP6_TEMPNAMES, ASMC_MP6_TEMPDESCS
+       },
+
   {
     "MacBookAir1,1", "Apple SMC MacBook Air",
     ASMC_SMS_FUNCS, ASMC_FAN_FUNCS, NULL, NULL, NULL,

diff -u original/asmcvar.h my-patch/asmcvar.h
--- original/asmcvar.h  2021-12-28 23:43:12.163365462 -0600
+++ my-patch/asmcvar.h  2021-12-29 00:11:36.207227372 -0600
@@ -581,6 +581,18 @@
           "Te3F", "Te3S", "Te4F", "Te4S", "Te5F", \
           "Te5S", "TeGG", "TeGP", "TeRG", "TeRP", \
           "TeRV", "Tp0C", "Tp1C", "TpPS", "TpTG", }
+
+#define ASMC_MP6_TEMPS { "TA0P", "TA1P", "TC0P", "TG0D", "TG0P", \
+       "TG1D", "TG1P", "TM0P", "TM1P", NULL }
+
+#define ASMC_MP6_TEMPNAMES     { "ambient_air_1", "ambient_air_2", \
+       "cpu_proximity", "gpu_diode_1", "gpu_proximity_1", "gpu_diode_2", \
+       "gpu_proximity_2", "mem_proximity_1", "mem_proximity_2" }
+
+#define ASMC_MP6_TEMPDESCS     { "Ambient Air 1", "Ambient Air 2", \
+       "CPU Proximity", "GPU Diode 1", "GPU Proximity 1", "GPU Diode 2", \
+       "GPU Proximity 2", "Memory Bank A", "Memory Bank B" }
+
 #define        ASMC_MBA_TEMPS          { "TB0T", NULL }
 #define        ASMC_MBA_TEMPNAMES      { "enclosure" }
 #define        ASMC_MBA_TEMPDESCS      { "Enclosure Bottom" }

cd /usr/src/sys/modules/asmc
make
make install
kldunload asmc
kldload /boot/modules/asmc.ko
# Check /var/log/messages for missing key entries

# Must add kld_list="/boot/modules/asmc.ko" to /etc/rc.conf instead of asmc_load="YES"
# in /boot/loader.conf so that we find our compiled version of the module

$ sysctl dev.asmc
dev.asmc.0.temp.mem_proximity_1: 42
dev.asmc.0.temp.mem_proximity_2: 41
dev.asmc.0.temp.gpu_proximity_1: 45
dev.asmc.0.temp.gpu_diode_1: 47
dev.asmc.0.temp.gpu_proximity_2: 44
dev.asmc.0.temp.gpu_diode_2: 47
dev.asmc.0.temp.cpu_proximity: 42
dev.asmc.0.temp.ambient_air_1: 37
dev.asmc.0.temp.ambient_air_2: 29
dev.asmc.0.fan.0.targetspeed: 790
dev.asmc.0.fan.0.maxspeed: 1900
dev.asmc.0.fan.0.minspeed: 790
dev.asmc.0.fan.0.safespeed: -1
dev.asmc.0.fan.0.speed: 789
dev.asmc.0.fan.0.id: Main
dev.asmc.0.%parent: acpi0
dev.asmc.0.%pnpinfo: _HID=APP0001 _UID=0 _CID=SMC-HURONRIVER
dev.asmc.0.%location: handle=\_SB_.PCI0.LPCB.SMC_
dev.asmc.0.%driver: asmc
dev.asmc.0.%desc: Apple SMC MacPro (2013)
dev.asmc.%parent: