Leopard performance on sub-867 MHz G4 hardware
I use one of my spare 400 MHz Sawtooth for testing things on occasion, and a few nights ago I was installing Leopard and testing performance. I went the more direct route to shoehorning it on by putting the drive in my 1.8GHz and installing it that way. I then put the drive in the 400 MHz again and it booted perfectly into a fully updated 10.5.8 install. No need to mess with firmware.
The performance was quite shockingly good to my delight. I opened Camino and Aurora with 4-5 tabs each then played 480p XviD in VLC 1.1.12, and had about 9% CPU to spare and no real system lag. After testing VLC playback I fired up MacTubes and was able to play the SD h.264 feeds perfectly smooth at approx. 81-82% CPU consumption. If you download the files with MacTubes, and play with VLC, or even play the feed in VLC; you can get away with even less CPU power, which makes a G4 350 MHz (AGP) a possibility to watch youtube with no frame drops. To be fair, the test system I'm using has 2GB RAM and an extra Geforce 6200 I have which supports every GUI/GPU feature in Leopard so those alone would help on any CPU.
This is even more proof that having a GPU with Core Image and Core Animation support is really what makes good Leopard performance. Without GPU hardware support for those built in can't turn off features in 10.5 you have to pay a CPU tax of up to 34%. This is because without CI/CA the OS uses the CPU to emulate the GPU. So anyone not running a Geforce 5200 or higher or a Radeon 9500 or higher under Leopard is literally slowing their CPU down as much as 34% and about 23% on average. The only way to actually disable all the GPU/GUI features in 10.5 that I have found is to have a tower and remove the video card. That means you can only remote into it.
The moral of the story is you're better off running Tiger if you have an unsupported GPU since it doesn't force the GPU features on the OS and CPU unless there is proper hardware support. If you do have GPU support then your 10.5 performance should be just as good, if not better. My two daily use Sawtooth both perform slightly better in all aspects on 10.5 and much better in OpenGL related code. A fully capable GPU is literally like an extra CPU in Leopard. In Tiger it's more of a slight benefit.
It's all about having the right hardware in the right places for the OS you run. The performance is amazing considering it's less than half the minimum CPU spec.
Test system specs:
G4 400 MHz 7400 w/1MB 2:1 L2
2 GB Memory
27 GB PATA HD
Geforce 6200 256 MB AGP
Published on Sunday, August 12, 2012