Micron sent us the P420m sans the black plastic cover that goes over the power-loss capacitors. With the internals exposed, we have a trio of boards, each with a specific purpose. The first board has the flash controller which is covered by a large heat sink. By ever so gently prying the heat sink off, we were able to see what makes this drive tick. As a side note, this process most definitely voided our warranty.
Even though the controller was produced by IDT, Micron had a heavy hand in its development and its firmware. The controller has 32 channels, and in this iteration, support for 64 NAND packages.
Moving through the board, we have 9 DRAM chips. Each DDR3 chip has a capacity of 256MB, giving us a total of 2.25GB.
The P420m utilizes 25nm MLC NAND; a departure from the SLC NAND used on the P320h. Each NAND package is made up of 8 die, with each die comprising 32Gb. The NAND is spread across 64 packages on two PCBs.
The P420m 1.4TB has a total of 2048GB of NAND. As we outlined in the P320h review, Micron’s RAIN technology uses 12.5% of that capacity for redundancy. RAIN allows for on the fly recovery of die failures, which is a great feature for enterprise customers. This leaves the P420m, just like the P320h, with ~22% over-provisioning.
Finally, the P420m, offers power-loss protection in the way of capacitors located on the third circuit board. This is the a new feature that the P320h did not have.