Overclocked QS'02 CPU - Crashes X, but 9 is perfectly fine?

[John8520]

Hello all!

I recently got a wonderful CPU module from herd for my Quicksilver. As a 1.87GHz 7448, it's more than powerful enough as is, but I've read good things about 7448s being overclocked so I wanted to try my luck. The die is marked 1700, so it already has a modest overclock, but some people have luck pushing 1.7s to 2.4, so why not try?

System specs:

• 1.87GHz 7448 (14x multiplier, 1.353v core voltage)
• 3x 512MB matched PC133 CL2 RAM
• Original Apple Geforce 4MX
• PCI SIL3112 w/ 256GB SSD attached (booting 10.5.8)
• 80GB ATA drive with 9.2.2

Here's what I tested, and my results from each of those tests.

• 1.87GHz / 1.353v (±50mV)
  • 9.2.2, 10.4.6, and 10.5.8 are all rock solid
• 2.00GHz / 1.405v (±50mV)
  • 9.2.2 - on ATA HDD - Perfectly rock solid. Macbench 5 numbers: 5617 CPU, 4944 FPU
  • 10.4.6 - booted from DVD drive - installer booted & was able to install okay
  • 10.4.6 - booted from ATA HDD - kind of works, but VERY unstable, crashes after a few minutes or doing anything CPU intensive (e.g. installing updates)
  • 10.5.8 - booted from SATA SSD - kernel panic within 10 seconds of seeing the grey apple logo
• 2.13GHz / 1.455v (±50mV)
  • 9.2.2 - on ATA HDD - Perfectly rock solid. Macbench 5 numbers: 6195 CPU, 5289 FPU
  • 10.4.6 - booted from DVD drive - KP within 10 seconds of grey apple
  • 10.4.6 - booted from ATA HDD - KP within 10 seconds of grey apple
  • 10.5.8 - booted from SATA SSD - KP within 10 seconds of grey apple
• 2.26GHz / 1.505v (±50mV)
  • 9.2.2 - on ATA HDD - Perfectly rock solid. Macbench 5 numbers: 6590 CPU, 5628 FPU
  • 10.4.6 - booted from DVD drive - KP within 10 seconds of grey apple
  • 10.4.6 - booted from ATA HDD - KP within 10 seconds of grey apple
  • 10.5.8 - booted from SATA SSD - KP within 10 seconds of grey apple
• 2.39GHz / 1.555v (±50mV)
  • System chimes, but doesn't display video or display booting activity (HDD/ODD noise)

Each time I made a change to the clock multiplier or core voltage I booted into 9 first, then tried X in its various configurations. Every time X failed, I tried to reconfigure it in different ways - e.g. pulling/swapping RAM, swapping the GPU, pulling the SIL3112 (when booting from the ATA drives, anyway) - none of those changes ever made any difference.

These results are really surprising to me. My past experience has been that OSX has been a lot more tolerant to "weird" system stuff than OS9 has been, yet here that is not the case at all. In every configuration that 9 boots in, I have been able to successfully: run Macbench 5 benchmarks, use dropstuff to compress about 200MB of files, run a Photoshop 7 task on a 45MB TIFF that takes approx. 20 minutes, and do other system tasks. Things that even on a good day OS9 might have trouble doing without crashing.

So... any ideas what's going on here? I know it's silly, but aesthetically I would very much like to have a ⩾2GHz OS9 booting G4 - which, I guess, technically I do have, but I want it to be able to boot OSX as well!

Also, for giggles... here's proof of my Macbench 5 numbers. (Check out the CPU speed on that last one!)

 

[adam25255]

Well, you cannot overclock G4 by 500MHz.

 

[demik]

OS X is putting way more pressure on the CPU/RAM than OS 9. It just means that your overclock isn't stable. How high is the temp ?

 

[John8520]

Well, you cannot overclock G4 by 500MHz.

What motivated you to dredge up a nine month old post simply to say this? Notice that nowhere in my post did I mention that a 500MHz overclock was something I expected to be successful, I simply tested it for the purposes of being thorough and, as expected, it was not successful.

The point of this post is that every speed below 2.39GHz, that is, 1.87GHz to 2.26GHz operates flawlessly in OS9, but is incredibly stable in OS X.

This is not a thread about overclocking a G4 by 500MHz.

OS X is putting way more pressure on the CPU/RAM than OS 9. It just means that your overclock isn't stable. How high is the temp ?

I've heard this theory a lot and, frankly, I don't buy it. At each speed between 1.87 and 2.26GHz I ran extensive benchmarks and CPU-load-generating tasks in OS9 and they all performed flawlessly. OS X, conversely, crashed within seconds of even starting to boot. One possibility is that it has something to do with AltiVec being unstable, but disabling it in Open Firmware nets no change.

 

[adam25255]

What motivated you to dredge up a nine month old post simply to say this? Notice that nowhere in my post did I mention that a 500MHz overclock was something I expected to be successful, I simply tested it for the purposes of being thorough and, as expected, it was not successful.

The point of this post is that every speed below 2.39GHz, that is, 1.87GHz to 2.26GHz operates flawlessly in OS9, but is incredibly stable in OS X.

This is not a thread about overclocking a G4 by 500MHz.




I've heard this theory a lot and, frankly, I don't buy it. At each speed between 1.87 and 2.26GHz I ran extensive benchmarks and CPU-load-generating tasks in OS9 and they all performed flawlessly. OS X, conversely, crashed within seconds of even starting to boot. One possibility is that it has something to do with AltiVec being unstable, but disabling it in Open Firmware nets no change.

Well, have not noticed that. Anyway, you expect 1700 rated board to work at 2Ghz+?(every CPU is different and you might fry it with that voltage) Definitely lucky it survived. Basically looked here and seen dumb thing.

Also you need better cooling.(thing that Japamacs has done) http://www.jcsenterprises.com/Japamacs_Page/Blog/FC8F8CD9-4D69-4FBA-9565-FB967FBC419F.html

OS 9 cannot use that powerful CPU, no Altivec implementation etc.(Actually runs on 60Mhz 601 too), so that is why you had no issues.

 

[John8520]

There are numerous reported instances of 1.7GHz marked 7448s running at 2.4GHz. It may not be common, but it is far from impossible.

Remember that, at 1.7GHz, the 7448 pulls all of 18W.

It's my own fault for not including this information (because, frankly, it is not relevant) but thermals are not an issue here. I have extensively tested and monitored the thermal capacity of this system and, believe me, it is completely suitable. This includes doing VERY CPU intensive tasks in OS9 (rendering a video in Final Cut for nearly two hours) with the machine door open. The heatsink temperature never went above 25ºC over ambient.

This is not a thermal issue.

 

[adam25255]

There are numerous reported instances of 1.7GHz marked 7448s running at 2.4GHz. It may not be common, but it is far from impossible.

Remember that, at 1.7GHz, the 7448 pulls all of 18W.

It's my own fault for not including this information (because, frankly, it is not relevant) but thermals are not an issue here. I have extensively tested and monitored the thermal capacity of this system and, believe me, it is completely suitable. This includes doing VERY CPU intensive tasks in OS9 (rendering a video in Final Cut for nearly two hours) with the machine door open. The heatsink temperature never went above 25ºC over ambient.

This is not a thermal issue.

Anyway, there is obvious difference between OS X and OS9. OS 9 will not make much use of G4. https://68kmla.org/bb/index.php?thr...ade-a-imac-g3-slot-loader-to-a-2ghz-g4.39394/ I have upgraded my CPU and really not much use of L3 cache and extra MHz.(still runs like utter dog because of cooperative multitasking)

Those people who buy 2GHz upgrade cards and GF4t for “Mac OS9 gaming”, despite feeling the same like B&W G3 with Rage 128.(OpenGL 1.2 limit)

Try it on Linux and will crash too.(UNIX systems are build completely differently) BTW no surprise it crashed with those systems like late Tiger and Leopard.(they are pretty resource heavy)

 

[Cory5412]

It sounds like John found a workload that's fully loading the G4 CPU under OS 9, fairly similar to what's possible under OS X, so I suspect think this (quoted) is what's going on here.

OS 9 will not make much use of G4

I haven't re-read my own posts in that thread in particularly close detail, but for what it's worth, what I meant is: Most people won't notice the speed boost in their day-to-day. Going faster isn't particularly important for the tourism the plurality of vintage Mac people want to do.

Critically, that's not that it's literally impossible for OS 9 software to use that speed boost, especially as you get into late-era games, multimedia authoring, and "technical computing" stuff like development and math software.

There is some AltiVec software for OS 9, although you'd be correct in noting that most of that also ran in OS X and, that, depending on your goals, you can get better results going to a duallie G4, a G5, or an Intel Mac.

I said "only reason" and, it's worth noting that "because I want to" is a fine enough reason, really. All of this stuff is ewaste and an Apple M1 will be something like a thousand times faster than any PPC Mac.

 

[herd]

I would guess that OSX is using some instruction (piece of logic in the CPU) that OS9 doesn't, and that instruction is not happy at higher clocks. Lightbulbfun has a OSX kernel made to run on 604 machines. Maybe this kernel would let OSX work at the higher speeds?

It seems to just be luck of the draw when overclocking these chips. I have an older 7447A marked 1333 that works fine at 2.13GHz. I also have an early production 7448 marked 1400 that works fine at 2.13GHz. I have never tried voltages that high though.

 

[jeremywork]

Altivec Fractal Carbon hits altivec pretty hard from OS 9. It's a bit bursty, but it was enough to toast one altivec unit in a 7410 I had clocked at 600MHz in a Pismo. It was stable before, but after looping Altivec Fractal Carbon about 10 minutes it now freezes immediately if anything tries to use it.

If that's been your issue it'll probably crash quickly.

Dauger Research, Inc., Altivec Fractal Carbon Page

Fractal calculations utilizing high-performance and cluster computing

daugerresearch.com

Also, I have one of the Dual 1.8 7447 boards (I think from NewerTech) in a Quicksilver, and when I first received it I found it very unstable in OS X. It would usually load the Tiger install DVD okay, but would panic or hang when trying to boot from the hard drive. Starting in verbose mode exposed a number of strange inconsistent errors. When I checked the manual for DIP switch settings the combo it had been set to wasn't one of the ones listed; setting it to the listed setting for 1.8GHz /133 bus dropped the clock speed from 1867 to 1800 but everything has been fast and stable since.
My memory is a bit hazy but IIRC it worked okay in OS 9, so I wonder if you're hitting the same type of instability...

 

[adam25255]

I would guess that OSX is using some instruction (piece of logic in the CPU) that OS9 doesn't, and that instruction is not happy at higher clocks. Lightbulbfun has a OSX kernel made to run on 604 machines. Maybe this kernel would let OSX work at the higher speeds?

It seems to just be luck of the draw when overclocking these chips. I have an older 7447A marked 1333 that works fine at 2.13GHz. I also have an early production 7448 marked 1400 that works fine at 2.13GHz. I have never tried voltages that high though.

Yeh, AltiVec in Leopard.(relies on it by large degree)

i sm curious what Puma or Jaguar do with overclock.

 

[Cory5412]

AltiVec is a big maybe. If you have a graphics card that supports Core Image, you can likely avoid it.

However - this same behavior is noted under 10.4 which does not require AltiVec, so I'm still a little bit skeptical on this theory.

A way to test it could be to run an altivec workload (like Final Cut...) in OS 9, except, notably here, John directly mentioned already having done that.

The only other thing I can think of that OS X uses (heavily) that OS 9 may be using much more lighly is memory management circuitry. Perhaps reducing the machine to 1x512MB and enabling VM could force 9 to use that more?

 

[greystash]

OSX does a CPU check on boot. I have a 1.8Ghz overclocked PowerBook G4 which will crash on any OSX system after booting. However, I installed the Snow Leopard PPC system which doesn't seem to check the CPU and it worked perfectly. No issues at all when running applications etc. OS9 usage was good including benchmarking tests, although I didn't use it much since it's officially unsupported there was no USB support for the trackpad which is annoying. I believe the CPU check was done when loading one of the OSX kexts but it was too long ago to remember, I may be wrong. This was a project I have put off working on for a long time