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CrissCross14

macrumors newbie
Original poster
Oct 2, 2022
5
1
I'd like to downgrade my Mac Pro 5,1 from Lion to snow leopard. No matter what I've tried, it simply won't work.

I tried flashing a retail disc to a USB, and then booting from that, but it gets stuck on an apple logo.
I also flashed the disc that (supposedly) came with the computer, but it spins on the apple logo for a bit, and then shows a "no entry" sign in place of the apple logo after about a minute or so.
(Image of the mac pro snow leopard disc: https://archive.org/details/691-674...nstall._Mac_OS_v10.6.4._Disc_v2.0_2010_DVD_DL)

Is there any way to install snow leopard on this computer? Or is there some sort of firmware lock that prevents snow leopard from being installed after a newer OS is installed?
 

tsialex

macrumors G5
Jun 13, 2016
12,662
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The issue is that when MacPro5,1 was released in July 2010, it was released with a special build of 10.6.4, with build number 10F2551 - this build is only available with MacPro5,1 factory restore disks and no other earlier build can run on a MacPro5,1 - you can't workaround that since all available media is older by a month than the required build and don't yet have added support for the MacPro5,1.

You can use some tricks to install Snow Leopard with the normal 10.6.3 or 10.6.4 retail disks, like doing it via virtualization with raw disk, Target Disk Mode connected to another older Mac where the retail disks work, but most people do it just moving the disk to an older Mac and installing it there.

After installing, you'll need to fully software update it, then you can move the disk to your Mac Pro and run the fully updated disk, now with 10.6.8.
 
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CrissCross14

macrumors newbie
Original poster
Oct 2, 2022
5
1
Updating the drive using raw disk on virtual box seemed to do the trick. I attached it to the VM as a usb drive and installed from there, then booted onto it from the startup disk menu and ran the combo installer on it.
 
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CrissCross14

macrumors newbie
Original poster
Oct 2, 2022
5
1
Hi, you can get the ISO DVD here:


Download it and burn a disc... that should do the trick...
I tried burning that to a usb, but booting it on the Mac Pro showed a "no entry" sign. Unfortunately I don't own any DL DVDs so I couldn't burn it onto a real DVD
 

tsialex

macrumors G5
Jun 13, 2016
12,662
12,936
Yes, the official 10.6.4 restore disk works with a Westmere Xeon equipped Mac Pro.
 

mrkapqa

macrumors 6502
Jan 7, 2012
415
69
Italy, Bolzano/Bozen
used it for quite some time, really fast, best OS on Intel Mac imo,
but you are limited to browser being newer Arctic Fox or Firefox legacy
you can buy install DVD on ebay, here in europe apple stopped selling these.
 

BrettApple

macrumors 65816
Apr 3, 2010
1,137
483
Heart of the midwest
Funny this thread was just active yesterday.

I acquired a Mac Pro 5,1 12-core recently and wanted to load the oldest OS possible because I loved Snow Leopard back in the day and it's far from a production machine for me.

Turns out, it's a pain in the butt! Why did I ever get rid of my 2008/9 era Macs!

I've got an Intel 2020 MacBook Pro 13" with Parallels though! And a retail copy of Snow Leopard and SL Server from back in the day (my own boxed copy!)

Solution right now:
  1. Create SL VM, boot it up.
  2. Install SL to the SSD going in to the Mac Pro via USB - SATA.
  3. Boot that up in the VM and install 10.6.8 combo update.
  4. Put SSD in Mac Pro. Profit.
Alternatively this should be do-able with USB Flash drive too. Install the OS to the VM or flash drive then use the combo update on the flash drive. Once done boot it up on the Mac and clone it to an internal drive with CCC or possibly Disk Utility. Keeping in mind they are USB 2.0 and quite slow doing this. But Snow Leopard is tiny compared to modern macOS releases.

1678769103744.png
 
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mrkapqa

macrumors 6502
Jan 7, 2012
415
69
Italy, Bolzano/Bozen
yes, having a second mac that can easily boot snow leopard dvd or boot from usb is one easiest method, then you can use firewire target disk mode to install from there to mac pro as destination , and fully upgrade to 10.6.8 via apple store updates (or if failing on snow leopard, via combo client update) before booting snow leopard directly from the mac pro.
my retail dvd was a 10.6.3 or 10.6, so i used also this method for macpro.
 

startergo

macrumors 601
Sep 20, 2018
4,703
2,155
These are the original DVD's:
Apple Mac Pro (2010) Mac OS X 10.6.4 Install DVD & Applications Install DVD

Notes
Disk 1 2Z691-6698-A
Disk 2 2Z691-6716-A

Compatibility
Apple Mac Pro (2010)

s-l1600.jpg
 
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startergo

macrumors 601
Sep 20, 2018
4,703
2,155
I was able to create a bootable USB for MacPro5,1 from the link in the first post:
Formatted the USB:
Code:
diskutil eraseDisk JHFS+ Untitled /dev/disk4
Converted the .toast file to DMG with disk utility and restored the DMG to usb:

Code:
sudo asr restore --source ~/Downloads/691-6744-A2ZMac_Pro_extracted/691-6744-A\,2Z\,Mac\ Pro.\ Mac\ OS\ X\ Install.\ Mac\ OS\ v10.6.4.\ Disc\ v2.0_2010\ \(DVD\ DL\)\ converted.dmg   --target /Volumes/Untitled --erase -noverify
 
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startergo

macrumors 601
Sep 20, 2018
4,703
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Last edited:

Dayo

macrumors 68020
Dec 21, 2018
2,167
1,228
Perhaps report to the OC team but there is more than one option for 10.6 there.
I think I used the iMac one.
 

MacNB2

macrumors 6502
Jul 21, 2021
294
213
I was able to create a bootable USB for MacPro5,1 from the link in the first post:
Formatted the USB:
Code:
eraseDisk JHFS+ Untitled /dev/disk4
Converted the .toast file to DMG with disk utility and restored the DMG to usb:

Code:
sudo asr restore --source ~/Downloads/691-6744-A2ZMac_Pro_extracted/691-6744-A\,2Z\,Mac\ Pro.\ Mac\ OS\ X\ Install.\ Mac\ OS\ v10.6.4.\ Disc\ v2.0_2010\ \(DVD\ DL\)\ converted.dmg   --target /Volumes/Untitled --erase -noverify
Thanks.
These steps worked for me on my cMP:
IMG_5160.jpg

Booted via OpenCore.

The download from Archive.org link above has different Apple part number......691-6744. (version 2.0) compared to what you listed above (Version 1.0)

Could not find a link to the Disc 2 (Applications)
 
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startergo

macrumors 601
Sep 20, 2018
4,703
2,155
Tested the second modified macOS installer:
  • 10.6.7-10J3250-ACDT-OSX.dmg (Modified MacBookPro8,x install disk, no SMBIOS lock)
And got the same exact freeze on the Apple logo.
Thanks.
These steps worked for me on my cMP:
View attachment 2250682

Booted via OpenCore.

The download from Archive.org link above has different Apple part number......691-6744. (version 2.0) compared to what you listed above (Version 1.0)

Could not find a link to the Disc 2 (Applications)
The Disk with the applications was selling on Ebay yesterday.
 
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startergo

macrumors 601
Sep 20, 2018
4,703
2,155
The download from Archive.org link above has different Apple part number......691-6744. (version 2.0) compared to what you listed above (Version 1.0)
Just checked the distribution file. This image only supports cMP5,1:
Code:
var hwbeSupportedMachines = [
 
        'MacPro5,1',
     
];

Apparently there are 2 versions of recovery DVD's for cMP5,1 (assuming this is a genuine image). For cMP4,1-->cMP5,1 conversion one needs to verify the return value of this check:
Code:
sysctl -n hw.model

Edit: There is a Mac Pro DVD with this p/n so it is genuine too:
Mac Pro Install DVD.jpeg
 
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MacNB2

macrumors 6502
Jul 21, 2021
294
213
Apparently there are 2 versions of recovery DVD's for cMP5,1 (assuming this is a genuine image). For cMP4,1-->cMP5,1 conversion one needs to verify the return value of this check:
Code:
sysctl -n hw.model

Good to know for those folks with cmp4,1.

I have one that's crossed flashed to 5,1 with cleaned and upgraded ROM by @tsialex.
So sysctl returns MacPro5,1 for me (while booted with that Snow Leopard Version 2.0 Install DVD)
 
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MacNB2

macrumors 6502
Jul 21, 2021
294
213
This might be kind of fun to boot on my cMPro. But is there an AMD RX-580 driver that has been adapted?
No but surprisingly usable with RX580 as it's seems fast enough without any drivers.

Only issue is if you have a 4K monitor then the GUI is in 4K which makes it hard to read the characters as they appear so small. You can get around that by setting UIScale=2 in OpenCore config which will make the default GUI 1080P.
 

Macschrauber

macrumors 68030
Dec 27, 2015
2,686
1,328
Germany
Good to know for those folks with cmp4,1.

I have one that's crossed flashed to 5,1 with cleaned and upgraded ROM by @tsialex.
So sysctl returns MacPro5,1 for me (while booted with that Snow Leopard Version 2.0 Install DVD)

Have you checked that? Regarding what this command reads it could be hwc from Nvram Fsys section. This is a 4,1 hwc. What is on most cmp 4,1 what have no factory refurbished board and 2010 5,1 identical with the last 3 chars of the system serial number.

I talk about what you see in >about your Mac< and what is in the firmware:

Code:
test_nvram_shell_script 22-Aug-2023 by Macschrauber
scanning: /Users/CKxxxxxxx4PD_144.0.0.0.0_rebuilt.bin

-> This is a never booted rebuilt firmware <-

Firmware 144.0.0.0.0 (latest) built on Fri Apr 12 12:43:00 2019
Bios Version: MP51.88Z.F000.B00.1904121248
MP41, Serial from firmware: CKxxxxxxxx4PD
LBSN: J59xxxxxxx1LTC   BD: 09xxxx09xxxx
hwc: 4PD   son: 000xxxxxxxxxx
CRC32 checksums: ok
Bootblock of 144.0.0.0.0 (rebuilt firmware)
Base_18 hardware descriptor
65448 bytes free space of 65464

where 4PD is one of the hardware codes for a MP4,1 - what is kept after a rebuilt / reconstructed firmware.
 
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tsialex

macrumors G5
Jun 13, 2016
12,662
12,936
Have you checked that? Regarding what this command reads it could be hwc from Nvram Fsys section. This is a 4,1 hwc. What is on most cmp 4,1 what have no factory refurbished board and 2010 5,1 identical with the last 3 chars of the system serial number.

I talk about what you see in >about your Mac< and what is in the firmware:

You are mixing very different things here. SSN, and consequently HWC, have nothing to do with the SMBIOS.

About My Mac is a remote query based exclusively on the Mac Pro System Serial Number. AboutMyMac parses the SSN, then query it with Apple servers. What you see is based on the answer the server returns.

The sysctl -n hw.model is based on a query to the Mac Pro SMBIOS SMproductname. Even if you flash mp51.fd to the BootROM (when the BootROM will be completely un-serialized) the sysctl -n hw.model will always answer MacPro5,1.

This is valid for a cross-flashed or a reconstructed early-2009 Mac Pro.

Code:
test_nvram_shell_script 22-Aug-2023 by Macschrauber
scanning: /Users/CKxxxxxxx4PD_144.0.0.0.0_rebuilt.bin

-> This is a never booted rebuilt firmware <-

Firmware 144.0.0.0.0 (latest) built on Fri Apr 12 12:43:00 2019
Bios Version: MP51.88Z.F000.B00.1904121248
MP41, Serial from firmware: CKxxxxxxxx4PD
LBSN: J59xxxxxxx1LTC   BD: 09xxxx09xxxx
hwc: 4PD   son: 000xxxxxxxxxx
CRC32 checksums: ok
Bootblock of 144.0.0.0.0 (rebuilt firmware)
Base_18 hardware descriptor
65448 bytes free space of 65464

where 4PD is one of the hardware codes for a MP4,1 - what is kept after a rebuilt / reconstructed firmware.

Again, this have nothing to do with SMproductname or hw.model.

Since we are talking about the macOS installer SMBIOS locks, for boards-id is more complex and varies between Macs, since some Macs have it set by straps or it's the T2 that answers it. One example of the former is the MacMini1,1 cross-flashed to MacMini2,1, it will continues to answer the board_id as the MacMini1,1 Mac-F4208EC8 instead of the MacMini2,1 Mac-F4208EAA and will not run an installer that have the Mac-F4208EC8 blacklisted. This happens to other Macs too.
 
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