Today we are taking a closer look at two Sandisk SSDs in the 256GB segment: the affordable Ultra Plus 256GB and the high-end Extreme II 240GB.
Sandisk is the biggest manufacturer of USB sticks and memory cards and also makes ToggleFlash flash chips. It has three SSD series with the Extreme II at the top, taking the place of the Extreme series. We tested the 240GB model which is available for an average of € 212. Positioned below it is the Ultra Plus series, of which we tested the 256 GB model. With an average price of € 176 for the desktop kit and € 159 for the notebook kit, it's cheap enough for Sandisk to potentially take a piece of the affordable SSD market. Currently, with € 0.62 per GB the Ultra Plus 256 GB is the cheapest 240-256 GB SSD we've tested. It's not even the entruy-level model, because there's also a series that's called just ‘Sandisk SSD’, but it costs almost the same as the Ultra Plus. We haven't tested that one (yet).
Sandisk Ultra Plus 256GB
The Ultra Plus 256GB is built around the Marvell 88SS9175, a version of the popular and previous-generation Marvell 88SS9174 controller. Marvell only delivers the hardware, so it's up to SSD manufacturers to develop good firmware with efficient algorithms. That's why SSDs using the same controller can differ widely in terms of performance. The 88SS9175 is very similar to the 88SS9174, but is supposed to be more energy-efficient.
The Ultra Plus 256GB has official read speeds up to 530 MB/s and write speeds up to 445 MB/s. The SSD uses proprietary MLC ToggleNand chips, with 19nm transistors. The flash memory has four instead of eight channels. By combining multiple dies on one chip, Sandisk only has to use four flash chips to get 256 GB of storage. That's why inside the Sandisk Ultra Plus 256GB the PCB is so tiny. On that we also find 128 MB DDR2 cache. The SSD measures 7mm in height and will therefor fin in all laptops.
Sandisk indicates that the SSD uses nCache. This means that part of the MLC flash memory (2 bits per cel) is used as SLC (1 bit per cel) in order to make faster writing possible. It's similar to the TurboWrite feature used on the Samsung 840 Evo. It's unclear exactly how much flash memory is used as nCache and how the algorithm works.
The notebook 'kit' consists of the SSD with a spacer to increase the height to 9.5mm. The slightly more expensive desktop kit contains a 3.5" installation bracket and a SATA cable, but lacks that spacer. You get 3 years of warranty, but there's not mention of a maximum number of writes.