"For Santa Rosa-based systems, the Intel ICH8 supports a SATA bus speed of up to 3.0 Gb/s. Lenovo made a design decision to prioritize maintaining compatibility with Ultrabay disk drives, which are connected via a SATA-to-PATA conversion chip which could not handle a 3.0 Gb/s SATA bus speed reliably. Therefore the system was standardized to 1.5 Gb/s.

In testing rotating media drives, our measurements show data throughput difference between 1.5 Gb/s and 3.0 Gb/s bus speed is less than 5% since the drive mechanics are the limiting throughput factor, rather than the SATA bus itself.   

For those customers who choose to purchase an after-market SSD drive capable of SATA bus speeds up to 3.0 Gb/s, the system will interface with them at 1.5 Gb/s. Lenovo's official position is that the Santa Rosa systems are working as designed.

The Montevina based systems which began shipping last year have direct SATA interfaces for both drive bays and are enabled at a system level for SATA bus speeds of 3.0 Gb/s performance. Current Lenovo drives have firmware set to 1.5 Gb/s data rates.

Exchanging these drives for after-market drives which support SATA bus of 3.0 Gb/s should provide for the higher data rate at the overall system level. Again, it should be noted that our performance measurements show less than 5% performance improvement between 1.5 Gb/s and 3.0 Gb/s SATA bus speeds for rotating drives, since the drive mechanics are the limiting throughput factor, rather than the SATA bus itself.

After-market SSDs which support SATA bus speed of 3.0 Gb/s will operate at that bus speed. Depending on the data transfer test method used, your actual data throughput from a 3.0 Gb/s SATA bus speed should be 220-250 MB/s and about 90-120MB/s throughput when running on SATA bus of 1.5 Gb/s. This is due to the bus signaling used for the SATA bus, as well as overhead for error checking."