Corsair sent out an email and posted some information on their website some of the implied criticism that is surrounding the transition from 34nm flash memory to 25nm flash memory on SandForce based SSDs.  Now, you might at first think that moving from 34nm flash to 25nm flash should be straight forward and any price benefits we get would be passed to the consumer with lower prices.  All good right?  Well, there is a catch:

Flash memory manufacturers are transitioning to using 25nm process for fabrication, allowing them to boost capacity and reduce costs, which in turn will allow SSD suppliers to pass those savings to the consumer. The downside is that SSDs built using 25nm flash ICs may require more over-provisioning (a technique used to ensure reliability) which lowers the capacity of the SSD and may also see a reduction in performance.

Overprovisioning is what SSD vendors much do to make sure that there is enough “spare” flash memory inside the drive to permit wear leveling patterns that extend the life of solid state drives to acceptable levels.  Essentially then, while you might have 256GB of flash memory inside the casing for an SSD, it is sold as a 240GB drive with 16GB used for overprovisioning, etc.  With the move to 25nm flash though a bit more memory is needed and thus we will see slightly smaller capacities in drives.

Corsair address the 25nm transition for SSDs, shows performance delta - Storage 3

So that our customers are perfectly clear about what they are getting, we will be changing the model numbers on all 25nm based drives and transitioning the drive capacities we offer where necessary. For example, a drive that would have been sold as 120GB when built with 34nm flash will be launched as a 115GB version,” said Jared Peck, Global Product Marketing Manager for SSDs at Corsair, “All Force Series drives built with 25nm flash will also have a ‘-A’ suffix on the part and/or model number, making it easy to determine exactly what you’re getting.”

That seems clear enough and should help prevent some of the backlash that hit OCZ when they started selling 25nm flash drives without indicating the change in capacity.  There is also a worry that performance of these new drives will be slightly lower than current 34nm revisions – and while that is true, the results seems to be pretty minimal.  Here is what Corsair had to say about it on its Force-series of 25nm drives:

In the Corsair Labs, using the ATTO synthetic benchmark, only a small reduction in performance (roughly 3-4%) was seen when testing Force Series SSDs built with 25nm flash.  Real-world tests, such as copying groups of files or measuring Windows boot times, support the ATTO results and show little to no performance loss. 

Corsair address the 25nm transition for SSDs, shows performance delta - Storage 4
Performance results from

We are working on getting a couple of 25nm variants from both Corsair and OCZ to make sure these performance claims are accurate, but we usually trust these guys when they are talking about performance this specifically. 

Corsair says that the new Force 25nm SSDs are going to be available by the end of February in both 115GB and 80GB versions.  MSRP of the F115-A is $215 while the F80-A will sell for $169 or so.  At $1.86 / GB for the F115-A, that is a decent price drop over the current MSRP of $249 for the 120GB model using 34nm flash.

If you are looking for the 180GB and 240GB revisions to hit this 25nm mix, you are going to have wait a bit longer.  John Beekley, VP of Technical Marketing, says that they will arrive in late March but that controller improvements by then will allow them to offer those models WITHOUT the increased overprovisioning, keeping usable capacities at 180GB and 240GB.  Nice!