@Mark - interesting results from the 'extensive' test.

New Shell process 9
Ram Disk:> cpu
System: PowerBook5,6
Machine: 0x1
PageSize: 4096 Bytes
CPUCount: 1
CPU0: 7447A (G4) Version 32771 Revision 258
CPU0: CPUClock 1666666660 BusClock 166483989
CPU0: FPU Unit exists
CPU0: Altivec Unit exists
CPU0: Performance Monitor Unit exists
CPU0: DataStream Unit exists
CPU0: ReservationSize 32
CPU0: Ticks 9
CPU0: CacheL1Type 0x0
CPU0: CacheL1Flags 0x1000F
CPU0: ICacheL1Size 32768
CPU0: ICacheL1Lines 1024
CPU0: ICacheL1LineSize 32
CPU0: DCacheL1Size 32768
CPU0: DCacheL1Lines 1024
CPU0: DCacheL1LineSize 32
CPU0: CacheL2Type 0x0
CPU0: CacheL2Flags 0x1001D
CPU0: ICacheL2Size 524288
CPU0: ICacheL2Lines 0
CPU0: ICacheL2LineSize 0
CPU0: DCacheL2Size 524288
CPU0: DCacheL2Lines 0
CPU0: DCacheL2LineSize 0
Ram Disk:> memtest extensive disable
Allocated memory at 0x3E60DDC0 -> 0x5CA83BFF, 507993664 bytes
Writing and Verifying 0x00000000...
Write 693 MB/sec. Verify 351 MB/sec.
Writing and Verifying 0xFFFFFFFF...
Write 693 MB/sec. Verify 351 MB/sec.
Writing and Verifying 0xFFFF0000... Write 840 MB/sec. Verify 410 MB/sec.
Writing and Verifying 0x0000FFFF... Write 840 MB/sec. Verify 410 MB/sec.
Writing and Verifying 0xFF00FF00... Write 840 MB/sec. Verify 410 MB/sec.
Writing and Verifying 0x00FF00FF... Write 840 MB/sec. Verify 410 MB/sec.
Writing and Verifying 0xF0F0F0F0... Write 840 MB/sec. Verify 410 MB/sec.
Writing and Verifying 0x0F0F0F0F... Write 840 MB/sec. Verify 410 MB/sec.
Writing and Verifying 0x55555555... Write 840 MB/sec. Verify 410 MB/sec.
Writing and Verifying 0xAAAAAAAA... Write 840 MB/sec. Verify 410 MB/sec.
Writing and Verifying 0xAAAA5555... Write 840 MB/sec. Verify 410 MB/sec.
Writing and Verifying 0x5555AAAA... Write 840 MB/sec. Verify 410 MB/sec.
Writing and Verifying 0xAA55AA55... Write 840 MB/sec. Verify 410 MB/sec.
Writing and Verifying 0x55AA55AA... Write 840 MB/sec. Verify 410 MB/sec.
Writing and Verifying 0xA5A5A5A5... Write 840 MB/sec. Verify 410 MB/sec.
Writing and Verifying 0x5A5A5A5A... Write 840 MB/sec. Verify 410 MB/sec.
Memory is ok!
Ram Disk:>