In April OCZ introduced its new Vertex 4 SSDs based on the Indilinx Everest 2 controller, which turned out being a new Marvell chip with Indilinx firmware. The Vertex 4 performed really well, and OCZ managed to keep the SSD affordable as well.
The last few months has seen a steady drop in SSD prices, with one manufacturer trying to outdo the other in terms of affordability. With the older Vertex 3 OCZ released a cheaper version to stay competitive, called the Agility 3. It's done the same now, launching the Agility 4.
The Vertex 3 and Agility 3 use the same SandForce SF-2281 controller, with one major difference. The Vertex 3 had synchronous flash memory, while the Agility 3 used the more affordable asynchronous flash memory. The same holds true for the Vertex 4 and Agility 4, as the Agility 4 comes with the same Everest 2 controller but with the cheaper type of memory.
Synchronous flash chips utilise a clock frequency in order to deliver data at pre-determined times. When a controller requests data from a synchronous flash chip it knows for sure when the data will be accessible. With asynchronous flash chips this discipline doesn't exist, it's just random. The flash chip will indicate when it's finished with a certain task, and in practice asynchronous chips are clearly slower.
The Agility 4 is available in 64, 128, 256 and 512 GB models. The two largest versions (of which we tested the 256 GB one) have reported read and write speeds of 400 MB/s. The 128 GB achieves 400/300 MB/s, according to OCZ, and the 64 GB does 300/200 MB/s. All of them are slower than the Vertex 4.
The selling point of the Agility 4 is its affordability. The 256 GB version we tested costs an average of £156, or £0.61 per GB. Other manufacturers have 256 GB SSDs that cost about the same, including the Crucial m4 and the Samsung 830. These will be the main competitors of the Agility 4, so let's find out which one is the best.