TL;DR - Booted Leopard (10.5.4ish) and overclocked 3.2GHz to 3.32GHz then warm reboot into 10.13.6 and retained overclocking. I know it isn't a huge amount and likely will be an 'unfelt change' but it's still fun.
So the other day I was poking around the net and ran into the really old threads about overclocking the cMP (back when it was the latest machine).
I had previously overclocked my MacPro3,1 2.8Ghz 8 core machine to something around 3.1Ghz, but as it relied on 32bit KEXT it didn't work reliably after Leopard since 64bit kernel became all the rage, and while some could get it to work using 32bit kernel in Lion (10.7) others could not. I used to be able to use it in Lion in 32bit kernel mode, however that no longer works for reasons I'm not sure of. (the app says i'm not using a supported platform as there is no response from the smbus controller name probe that it does). The date/time clock skew issue also turned some people off from this as only the 3,1 had a way around this (warm reboot keeps OC but corrects the clock skew and allows you to boot any other OS and retain OC)
I started playing around with getting an old 32bit kernel OS to boot, Lion was my first choice as it was the most recent one with 32bit kernel option. Got it installed and fired up the ZDNet app to have it tell me that it wasn't a supported platform. Then decided to try Leopard instead as that was new when this app was new and figured it would be the best chance. I was really wondering if this wasn't working as I had swapped my processors a couple years ago with the dual quad 3.2GHz ones replacing the dual quad 2.8GHz ones I bought new.
After some issues getting Leopard to boot, (MP3,1 I believe requires 10.5.2 in order to boot without panic) and my own hardware changes (extra SATA3 controller, extra RAID cards, GTX650) I ended up with a 10.5.4-ish setup, kernel from 10.5.8 and the AHCI kext from 10.5.8 added to the 10.5.4 base, along with removal of all NVDA and GeForce kexts / plugins. Not doing this just meant panic or getting stuck at the end of the boot process as it couldn't load graphics properly (GTX650 support didn't arrive until 10.7.4)
Man Leopard is FAST on SSD even when just using Software renderer for the GPU, boot is crazy fast and GUI is loaded "now". It probably takes 10x longer to boot 10.13 vs 10.5 on the same hardware. I also got the joy of listening to the welcome video (didn't display since I don't have GPU accel) while I was going through the initial setup wizard, man have things changed there (we used to have all sorts of optional install items and just a better UX / UI in my opinion).
So hybrid Leopard loaded the overclock.kext without issue and the app detected my MacPro correctly.
I had several hangs and panics attempting to get the overclock going as high as I could.
It seems finicky, meaning if I can get it to 408MHz on FSB then I can get to 415MHz (giving 3.32GHz effective clock) I have to slowly step up the frequency it seems, getting over the 407/408 point is panic prone. (incidentally found out that Apple blocks panic reports from 10.5 from being received on their end)
I did manage to get over the 415MHz point once but wasn't able to repeat it.
I do have 3 densities of RAM installed (1G, 2G, 4G) all of differing brands, which likely is where the issues come from, in one panic report it was machine check exception (pointing at ECC that wasn't able to be recovered) I'd bet with better / consistent RAM setup I could get higher. RAM gets OC'd along with CPU and FSB with this method of OC.
Now in 10.13 you can't seem to locate any evidence that you have a higher than stock clock rate.
All types of benchmark apps seem to see 3.2GHz.
I did manage to find one sysctl that shows the higher rate (showing the rest of the frequency info for posterity).
And oddly enough the Win10 VM sees the higher clock rate, but my Linux VM doesn't.
I've only shared 3 cores with Win 10 (mcafee on-access scanner is pegging CPU):
Geekbench doesn't see the clock change either:
https://browser.geekbench.com/v4/cpu/9696485
So the other day I was poking around the net and ran into the really old threads about overclocking the cMP (back when it was the latest machine).
I had previously overclocked my MacPro3,1 2.8Ghz 8 core machine to something around 3.1Ghz, but as it relied on 32bit KEXT it didn't work reliably after Leopard since 64bit kernel became all the rage, and while some could get it to work using 32bit kernel in Lion (10.7) others could not. I used to be able to use it in Lion in 32bit kernel mode, however that no longer works for reasons I'm not sure of. (the app says i'm not using a supported platform as there is no response from the smbus controller name probe that it does). The date/time clock skew issue also turned some people off from this as only the 3,1 had a way around this (warm reboot keeps OC but corrects the clock skew and allows you to boot any other OS and retain OC)
I started playing around with getting an old 32bit kernel OS to boot, Lion was my first choice as it was the most recent one with 32bit kernel option. Got it installed and fired up the ZDNet app to have it tell me that it wasn't a supported platform. Then decided to try Leopard instead as that was new when this app was new and figured it would be the best chance. I was really wondering if this wasn't working as I had swapped my processors a couple years ago with the dual quad 3.2GHz ones replacing the dual quad 2.8GHz ones I bought new.
After some issues getting Leopard to boot, (MP3,1 I believe requires 10.5.2 in order to boot without panic) and my own hardware changes (extra SATA3 controller, extra RAID cards, GTX650) I ended up with a 10.5.4-ish setup, kernel from 10.5.8 and the AHCI kext from 10.5.8 added to the 10.5.4 base, along with removal of all NVDA and GeForce kexts / plugins. Not doing this just meant panic or getting stuck at the end of the boot process as it couldn't load graphics properly (GTX650 support didn't arrive until 10.7.4)
Man Leopard is FAST on SSD even when just using Software renderer for the GPU, boot is crazy fast and GUI is loaded "now". It probably takes 10x longer to boot 10.13 vs 10.5 on the same hardware. I also got the joy of listening to the welcome video (didn't display since I don't have GPU accel) while I was going through the initial setup wizard, man have things changed there (we used to have all sorts of optional install items and just a better UX / UI in my opinion).
So hybrid Leopard loaded the overclock.kext without issue and the app detected my MacPro correctly.
I had several hangs and panics attempting to get the overclock going as high as I could.
It seems finicky, meaning if I can get it to 408MHz on FSB then I can get to 415MHz (giving 3.32GHz effective clock) I have to slowly step up the frequency it seems, getting over the 407/408 point is panic prone. (incidentally found out that Apple blocks panic reports from 10.5 from being received on their end)
I did manage to get over the 415MHz point once but wasn't able to repeat it.
I do have 3 densities of RAM installed (1G, 2G, 4G) all of differing brands, which likely is where the issues come from, in one panic report it was machine check exception (pointing at ECC that wasn't able to be recovered) I'd bet with better / consistent RAM setup I could get higher. RAM gets OC'd along with CPU and FSB with this method of OC.
Now in 10.13 you can't seem to locate any evidence that you have a higher than stock clock rate.
All types of benchmark apps seem to see 3.2GHz.
I did manage to find one sysctl that shows the higher rate (showing the rest of the frequency info for posterity).
Code:
macpro-osx:~ ludacrisvp$ sysctl -a |grep freq
hw.busfrequency: 1600000000
hw.busfrequency_min: 1600000000
hw.busfrequency_max: 1600000000
hw.cpufrequency: 3200000000
hw.cpufrequency_min: 3200000000
hw.cpufrequency_max: 3200000000
hw.tbfrequency: 1000000000
machdep.tsc.frequency: 3321817762And oddly enough the Win10 VM sees the higher clock rate, but my Linux VM doesn't.
I've only shared 3 cores with Win 10 (mcafee on-access scanner is pegging CPU):
Geekbench doesn't see the clock change either:
https://browser.geekbench.com/v4/cpu/9696485
