IIRC, it was the 680x0's that so often had the crippled memory bus.
The slowness on the PowerPC probably had more to do with the CPU power. PowerMacs struggled to be competitive with Pentiums for integer computation, and often the PowerPC Macs were not clocked competitively against their PC brethren.
You referenced a 601... The PowerPC 601 based machines still had NuBus, which was slow compared to VLB & PCI.
All the early PowerPC had a variety of disadvantages slowing them down: 680x0 emulation blowing the processor cache at times (particularly the 603), built in graphics were generally pathetic (and often used RAM as VRAM, undermining the value of the fast memory bus for gaming... but if you installed your own card with dedicated memory that problem vanished), and a the graphics card market was skewed for desktop publishing making it very costly to get good gaming performance.
Of course Apple abused benchmark stats to make it all seem much faster than it was, but the memory bus was derived from the Motorola 88100 bus, and consequently was pretty decent (and if you think about it, the afore mentioned 486dx4 actually had a memory bus that was running about a third of CPU speed...).
Radius graphics cards used to have fantastic blit performance.
Some PowerPC Macs were particularly crippled, such as the x200 series, using a 64-bit PPC CPU on 32-bit data bus, and memory running as low as 1/2 to 1/3 CPU speed. Because of the horrible design, heavy network traffic would critically slow the machine. See more info here: http://lowendmac.com/2014/power-mac-and-performa-x200-road-a...
The 603 in the x200's was a 32-bit CPU, and it explicitly supported 32-bit memory bus interfaces. That was part of how it kept costs down. In short, not a bug, but a feature (and there was support for interleaving to get you some of the benefits of a 64-bit bus). As per the link, the clock speed of the CPU was 90-120MHz. No PC was using 90-120MHz memory. They were all dropping to 1/2 & 1/3 (including Pentiums you are comparing against).
I think there is some confusion on the part of the author of that LEM post. The processor was indeed 32-bit but the data path was 64-bit. /shrug
On that note, I finally found the link I was originally looking for - a later post which goes into way more detail as to the flaws of these systems. I can vouch for the unbelievable slowness of these machines as I used one for years. haha :(
The data path was 64-bit, but it was designed to support being married up to a 32-bit bus. That was part of how they were a more appealing choice than a 604 processor.
The slowness on the PowerPC probably had more to do with the CPU power. PowerMacs struggled to be competitive with Pentiums for integer computation, and often the PowerPC Macs were not clocked competitively against their PC brethren.
You referenced a 601... The PowerPC 601 based machines still had NuBus, which was slow compared to VLB & PCI.
All the early PowerPC had a variety of disadvantages slowing them down: 680x0 emulation blowing the processor cache at times (particularly the 603), built in graphics were generally pathetic (and often used RAM as VRAM, undermining the value of the fast memory bus for gaming... but if you installed your own card with dedicated memory that problem vanished), and a the graphics card market was skewed for desktop publishing making it very costly to get good gaming performance.
Of course Apple abused benchmark stats to make it all seem much faster than it was, but the memory bus was derived from the Motorola 88100 bus, and consequently was pretty decent (and if you think about it, the afore mentioned 486dx4 actually had a memory bus that was running about a third of CPU speed...).
Radius graphics cards used to have fantastic blit performance.