AMD 990X / SB950 chipset
The AMD SB950 south bridge on the AMD 990FX chipset has six SATA 600 ports. We have repeatedly said that this is an advantage, but the question is whether the chipset is powerful enough to manage good transfer rates on all six ports. We connected the six OCZ SSDs to an ASUS Crosshair V Formula motherboard with an AMD FX-8150 processor. We used only the latest drivers.
Let's get to the meat right away. The AMD SATA controllers have inferior performance compared to Intel's. With a single disk the performance is still acceptable. The Vertex 4 in AS SSD scores 868 points with Intel, and 793 with AMD. Not a huge difference, but still.
Two SSDs in RAID 0 with AMD reach 1,088 points, where Intel had 1,249 points. What happens next is noteworthy, when we go from three to four SSDs there is almost no performance increase. With more than four drives the performance pretty much remains the same.
The sequential read speed increases from 439 MB/s with one SSD to 896 MB/s with six SSDs. Intel performs much better here. However, in terms of write speed AMD actually outperforms Intel. Intel went from 185 MB/s to 1,014 MB/s, while AMD goes from 177 MB/s to 1,087 MB/s.
AMD really struggles with the read and write speeds with 64 simultaneous threads. After three SSDs these remain constant, while Intel kept scaling nicely. It is also the primary reason for the lower AS SSD scores.
|AMD SB950||1 SSD||2 SSDs||3 SSDs||4 SSDs||5 SSDs||6 SSDs|
|Read - 4KB||25,94||28,44||28,66||28,64||28,1||26,83|
|Read - 4KB 64 THRD||284,2||352,21||336,43||325,94||311,55||307,66|
|Read - Access time
|Write - 4KB||82,74||75,41||75,85||76,26||72,89||76,89|
|Write - 4KB 64 THRD||161,3||324,96||335,36||329,41||324,54||324,14|
|Write - Access time