I don't know about memory starved. This from Newtek forums, posted by Chris Cox of Photoshop fame.
[quote]--SNIP--
133 MHz bus means nothing, except in comparison to other PowerPC chips with different bus speed. The throughput (bandwidth) of the bus is what matters.
The Athlon XP has a 200 MHz double clocked bus and uses DDR DRAM -- but can only move 700 MB/s (on a good day).
The P4 has a fast bus and dual channel RDRAM and can move 1500 MB/s -- but only on very simple operations like memcpy, memset, memcmp. For complex operations it's not much better than PC133 (where it only moves about 600 MB/s).
The PowerMac G4 has a lowly 133 MHz bus, and moves 1085 MB/s, sustained over large (32 Meg) buffers. For less optimized code it can sustain 930 MB/s (again over large buffers).
Why is the slowest bus moving so much memory? Better bus design, better DRAM controller, better cache design, and several other details that only serious solderheads would understand.
Oh, and clockspeeds -- again, the number doesn't matter. Throughput (in this case computation completion) matters. That's why a P4 at 1500 MHz is usually slower than a P3 at 1000 MHz, and an Athlon XP at 1.6 GHz runs circles around a P4 at 2.0 GHz. The PowerPC has a lower clockspeed - sure. But it also has lower latencies, larger caches, more functional units, more pipelining, better cache control, and lots of other things that make it competitive with Intel chips at over twice the clockspeed.
--SNIP--
About the only disadvantage I've found on the G4 is the ATA66 supplied on the motherboard. But I normally replace that with a Ultra160 card anyway.<hr></blockquote>
The point is, with DDR, we could be moving 2GB+ , all else being equal. And even if MPX can move X amount of data under certain conditions, that doesn't mean the processor doesn't ever end up waiting for RAM. What Chris said is true, but it doesn't preclude what we're talking about here. In essence he's arguing something different....
Comments
[quote]--SNIP--
133 MHz bus means nothing, except in comparison to other PowerPC chips with different bus speed. The throughput (bandwidth) of the bus is what matters.
The Athlon XP has a 200 MHz double clocked bus and uses DDR DRAM -- but can only move 700 MB/s (on a good day).
The P4 has a fast bus and dual channel RDRAM and can move 1500 MB/s -- but only on very simple operations like memcpy, memset, memcmp. For complex operations it's not much better than PC133 (where it only moves about 600 MB/s).
The PowerMac G4 has a lowly 133 MHz bus, and moves 1085 MB/s, sustained over large (32 Meg) buffers. For less optimized code it can sustain 930 MB/s (again over large buffers).
Why is the slowest bus moving so much memory? Better bus design, better DRAM controller, better cache design, and several other details that only serious solderheads would understand.
Oh, and clockspeeds -- again, the number doesn't matter. Throughput (in this case computation completion) matters. That's why a P4 at 1500 MHz is usually slower than a P3 at 1000 MHz, and an Athlon XP at 1.6 GHz runs circles around a P4 at 2.0 GHz. The PowerPC has a lower clockspeed - sure. But it also has lower latencies, larger caches, more functional units, more pipelining, better cache control, and lots of other things that make it competitive with Intel chips at over twice the clockspeed.
--SNIP--
About the only disadvantage I've found on the G4 is the ATA66 supplied on the motherboard. But I normally replace that with a Ultra160 card anyway.<hr></blockquote>