The fastest AGP slot in a Mac is 32-bit 66 MHz 4X = 1067 MB/s.
No Mac implemented AGP 8X.
All the G5's have 8X AGP???
Some of the 64-bit PCI cards can approach the theoretical maximum of 267MB/s in a G4, but I have not found a way to boot from them. With linux I think there is a way to boot on something slow and then change over.
68kmla.org/bb/index.php?threads/g4-raid.40817/
In a G3 (or earlier PPC?), I would be surprised to see anything over 100MB/s because not even the RAM is that fast.
I've seen benchmarks of the B&W hitting near the 266MB/s on 64 bit PCI RAID controllers.
If the RAM can't move data that fast, what is it, magic?
Would have rather used a larger size ... not that it would probably make a ton difference. But who knows ?
Generally speaking the lower numbers, 32k-1024k are going to be some of your slowest benchmarks.
Try and use a real benchmarking tool, not XBench.
A 64-bit bus at 100MHz has a theoretical peak speed of 800MB/s (8 bytes at 100MHz). So I'm guessing the 266MB/s that you mentioned is the theoretical peak speed of a 33MHz bus?
I forgot the systems bus was a 64bit data path.
Let me give you another example. I have a 1.1GHz 750G G3 CPU in an AGP with a 100MHz bus (theoretical speed of 800MB/s). Using the AJA System Test with file system cache enabled basically results in a RAM test until the file size exceeds the available RAM. Even with the super G3, the throughput is around 100MB/s. Swapping in a 300MHz 7400 G4 CPU (no other change), results in 350MB/s.
AltiVec has always speeded up memory operations.
This is why I think that even with a fast 64-bit PCI card for disk IO (267MB/s peak) a G3 machine will not be able to move data any faster than what it can do with RAM.
We don't really have a great benchmark for systems RAM for PPC on the Mac OS, if
@joevt can write us one we may have some idea how fast the memory is real moving.
Disk IO and RAM are always related when we have DMA involved, so you're not side tracking things.
With everything up to the G5 we only had SDRAM( except the OW ) so it just runs at the system bus speed in a 64bit path, theoretically. Real world test show we rarely get 266MB/s out of the lower end NWM's.
The Beige G3 was kind of a dog, the B&W/Yikes were better, then they started cranking up the bus for real.
With drive controllers on a PCI Bus there is a lot of overhead and really only Atto really did great work there on PPC