Last year Marvell announced updated client NVMe controllers that we have not yet encountered in the retail SSD market, but now that the transition to PCIe gen4 is underway those controllers are already due for replacement. The new family of controllers reflect shifts in the market that Marvell is expecting, and are intended more for OEM SSDs than retail products. (Silicon Motion and Phison have almost completely displaced Marvell from the retail consumer SSD market.)
As NAND flash interface speeds and per-die capacities are increasing, Marvell is betting that mainstream client NVMe products can get away with just four NAND channels rather than eight. They’re also making DRAMless SSDs (optionally with NVMe Host Memory Buffer support) a bigger part of their strategy. Those two changes combined means controllers can be physically much smaller, and Marvell expects shorter M.2 cards like the 22x30mm size to become much more popular now that they can offer higher performance and capacities up to 2TB (when using QLC NAND).
Marvell’s new generation of client NVMe controllers consists of three products: DRAMless controllers with two or four lanes of PCIe gen4, and one controller with DRAM support and four lanes of PCIe gen4. All three controllers have four NAND channels, but the largest 88SS1321 that has the DRAM interface also has twice as many chip enables on the NAND channels and thus can support higher capacities than the DRAMless 88SS1322 and 88SS1323.
|Marvell Client NVMe SSD Controller Comparsion|
|Market Segment||Consumer, Entry-level Datacenter||Mainstream Consumer||Mainstream Consumer||High-end Consumer||Consumer &
|CPU Cores||3x Cortex R5||4x Cortex R5||3x Cortex R5|
|Host Interface||PCIe 4.0 x4||PCIe 4.0 x2||PCIe 3.0 x4||PCIe 3.0 x4|
|NAND Interface||4 channels,
|8 channels, 800MT/s||8 channels, 533MT/s|
|Sequential Read||3.9 GB/s||3.9 GB/s||3.5 GB/s||3.0 GB/s||3.6 GB/s||3.2 GB/s|
|Sequential Write||3.3 GB/s||3.3 GB/s||3.0 GB/s||2.6 GB/s||3.0 GB/s||2.0 GB/s|
|4KB Random Read||690k IOPS||500k IOPS||450k IOPS||450k IOPS||780k IOPS||300k IOPS|
|4KB Random Write||500k IOPS||350k IOPS||300k IOPS||400k IOPS||650k IOPS||250k IOPS|
|Announced||August 2019||June 2018||August 2014|
The sequential IO performance of the new 4-channel controllers is only slightly better than Marvell’s earlier 8-channel controller, and random IO has taken a step backward. Marvell isn’t aiming to saturate a PCIe 4 x4 link, though the smallest 88SS1323 with only a PCIe 4 x2 link does hit the speeds we’re used to seeing from PCIe 3 x4 SSDs.
Instead, Marvel is touting that they have the most power-efficient PCIe Gen4-capable SSD controllers, addressing concerns raised by AMD’s latest chipsets and the Phison E16 SSD controller about PCIe 4 being a power hog. Marvell’s new DRAMless controllers run at less than 2W with a PCIe 4 x4 link active, which isn’t much more than the NAND flash itself requires. This is made possible by Marvell’s jump to 12nm fabrication, compared to 28nm that has been the standard for most NVMe controllers. Even though these controllers are using a relatively advanced fab process, Marvell says they will allow for very cost-effective SSDs, especially when used in DRAMless configurations.
Aside from the faster PCIe and NAND interfaces, the new generation of controllers are architecturally similar to their predecessors, with a handful of Arm Cortex R5 CPU cores and the same fourth-generation LDPC engine used by last year’s controllers from Marvell.
Marvell is currently sampling the new controllers, and will be showing them off next week at Flash Memory Summit.