OCZ RevoDrive Review: SSD RAID + PCI-Express
The RevoDrive's specs—up to 540MB/s read and 480MB/s writes—come courtesy of its onboard Silicon Image 3124 RAID controller. The card can be configured for RAID Level 0 or RAID Level 1; presumably most consumers will opt to utilize RAID 0 and provide an HDD-based backup solution. We're surprised to see the SiI 3124 putting in an appearance; the controller is over six years old and only supports PCI/PCI-X.
She may not look like much but she's got it where it counts...we hope.
It turns out, however, that this is one area where OCZ has cut cost to keep the RevoDrive affordable. The SiI 3124 connects directly to the Pericom PI7C9X130 bridge chip below it; it's this second processor that connects to the x4 PCI-Express slot. According to the company, it was cheaper to bridge the SiI 3124 than it was to buy a native controller; this decision is part of why the 120GB RevoDrive carries a price tag of just $369.
The Pericom bridge chip: Part of the RevoDrive's secret sauce.
The SiI 3124 should be adequate to the task at hand, but there are a few limitations to consider. Access latencies could be slightly higher, due to the use of a bridge chip, and the controller's PCI-X interface could cause oddities of its own. At 64-bits wide and an operating speed of 133MHz, the SiI 3124 RAID controller has a maximum throughput of 1.06GB/s(half-duplex). That's significantly less than the 800MB/s of full-duplex bandwidth a native PCIe x4 controller would've provided, but it shouldn't prove a problem in a two-drive RAID 0.
In the image above, the Silicon Image 3124 is underneath the stylized "R". The bridge processor is just below that. The center connector is an attach point for a second PCB—OCZ could release a four-way card at some point.
There are a few additional caveats. The drive doesn't support idle garbage collection and neither AHCI nor TRIM are available. Full AHCI support wasn't an original feature of the SiI 3124 (although Native Command Queuing, or NCQ, is supported). As for TRIM and garbage collection, the intervening RAID controller prevents either function from operating.