Hah well spotted and the values for the Intel drives are GiB (even though the Intel manual reports them as GB). Better change that before John gives me a bollocking

Anyway with your 830 did you record 199 when your read/ write speeds were messed up?

(199) UltraDMA CRC Error Count
This is generally the literal count of how many times the controller encountered an error while processing an ATA command in UDMA mode. It also counts how many times a CRC checksum has mismatched during operations. Usually, this indicates a problem with the cabling or drive electronics. These errors can also be triggered by incorrect IDE device chaining or simply a faulty IDE or SATA cable, or when device firmware bug match some chipset detection problem (SATA II at 3.0Gb/s drive misdetecting SATA I at 1.5Gb/s bus controller).