@ Oepabakkes
Ran tests on a similar processor (a 733Mhz overclocked to 933Mhz). installed on a Quicksilver Powermac.
I got similar (disappointing) memory figures.
I will run the tests again once I receive the Sonnett 1.8 Ghz 7447 CPU I ordered

Ram Disk:> cpu
System: PowerMac3,5
Machine: 0x1
PageSize: 4096 Bytes
CPUCount: 1
CPU0: 7451 (G4) Version 32768 Revision 513
CPU0: CPUClock 933333331 BusClock 133160004
CPU0: FPU Unit exists
CPU0: Altivec Unit exists
CPU0: Performance Monitor Unit exists
CPU0: DataStream Unit exists
CPU0: ReservationSize 32
CPU0: Ticks 4
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 262144
CPU0: ICacheL2Lines 0
CPU0: ICacheL2LineSize 0
CPU0: DCacheL2Size 262144
CPU0: DCacheL2Lines 0
CPU0: DCacheL2LineSize 0

Ram Disk:> memtest disable
Allocated memory at 0x33491800 -> 0x3DA906FF, 174059264 bytes
Writing and Verifying 0x00000000...
Write 261 MB/sec. Verify 352 MB/sec.
Writing and Verifying 0xFFFFFFFF... Write 262 MB/sec. Verify 352 MB/sec.
Memory is ok!