[Armando]

I was poking around the Mac Mini manual (the .PDF file) and it shows a screenshot of the System Profile with a 333Mhz bus speed. My Mac Mini shows a 167Mhz bus speed. Everybody out there have 167Mhz bus speed? Or should it be 333Mhz? I have a feeling Apple slowed down the bus speed.

Check this out:

[chabig]

That's interesting. It must be a quirk of the pre-release system in use when they made the manual. But 167MHz is the correct number. I am fairly certain that no version of the G4 chip supports a 333MHz bus.

Chris

[andreas_g4]

Right. Not being a Processor expert, but I recall rather clear that the BUS was the biggest bottleneck of the overall G4 architecture. I guess it tops out a 167 MHz max. Even the 2x 1.42 GHz has only 167 MHz.

Maybe they had a prototyep running with a new freescale chip… just guessing.

[andreas_g4]

Besides that, memory reads 256 kb, which should be MB, because it's not the cache. Maybe the whole Sysinfo is just messed up…

[typoon]

Also notice the boot ROM version. On my Mini it's 4.8.9 f1. The older boot rom could just be reporting it wrong.

[power142]

From the general benchmarks I've seen posted, the G4 scales fairly linearly, at least up as far as the 1.5GHz Powerbook models. That might lead us to the conclusion that the bus isn't such a horrific bottleneck in a single processor setup as it is in the dual processor models (and hence the reason for the big 2MB L3 cache on the high-end dual processor MDD models).

167MHz isn't so bad. DDR400 hasn't always been the dominant memory type, and after all it's really 200MHz doubled in certain circumstances. Fair call that the G4 doesn't support DDR, but DDR only helps when bursting large blocks of data and doesn't help much with normal use random memory accesses. As such, the lack of DDR support of the G4 chip might actually throttle back the AltiVec unit more than anything else. Synthetic memory throughput benchmarks are all well and good, but don't realistically reflect the normal usage pattern of a machine like the mini.

[Simon]

That manual image is just screwed. As pointed out it's also not 256 KB of RAM.

167MHz is correct, it's the highest clock the 75x/74xx CPUs support. 333 MHz is basically the 'memory bus data rate', since per clock cycle, the DDR bus can push two signals (one on the rising and one on the falling edge of the clock signal).

They probably just tinkered another system profiler picture in order to write the manual for the mini. If your mini boots fine, your clock is running just right. I wouldn't worry about it.