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> The Tom's review of the revised Crucial P2 500GB was a 2-chip and the QN322 2TB also appears to be 2-chip vs 1-chip for smaller capacities of the QN322, so th
by wtallis 4y ago
> The Tom's review of the revised Crucial P2 500GB was a 2-chip and the QN322 2TB also appears to be 2-chip vs 1-chip for smaller capacities of the QN322, so the performance boost from higher capacity won't be there.
You need to make the distinction between how many packages of NAND flash are soldered to the PCB, and how many dies of NAND are stacked in one BGA package. A 2TB SSD requires more than two NAND dies because the largest NAND dies in production are in the ballpark of 1-1.33Tbit, so a 2TByte drive would typically have 16 NAND dies in total.
> And the SLC cache size isn't fixed but rather a fraction of the free space.
That doesn't stop a 2TB drive from generally having 4x more SLC cache than a 500GB drive, other things being equal.
- tbyehl 4y agoThe published specs don't tell us how many layers of NAND there are, but they do claim the 2TB is only 1.8X the write performance of the 500GB and 1.125X the 1TB. Not the 4X you'd speculated. If you have a QN322, feel free to provide benchmark results.
- wtallis 4y agoNAND layers is another question entirely: that's about how many layers of memory cells each die has, not about how the dies are packaged together. And of course the performance specs for the 2TB don't show it being 4x faster than the 500GB model: those specs are for peak performance when using the SLC cache. Consumer SSD specs almost never list post-cache performance. I don't have one of the drive in question, but unlike you I actually know enough about how these things work to know what performance claims are plausible or not. (See eg. https://www.anandtech.com/show/16681 https://www.anandtech.com/show/16681 https://www.anandtech.com/show/16577 https://www.anandtech.com/show/16577 https://www.anandtech.com/show/16491 https://www.anandtech.com/show/16491 )