Silicon Motion Demos Low-Power PCie 5.0 SSD Controller: SM2508

Rounding out our Computex 2024 SSD controller news, let’s talk about the final major controller vendor at the show: Silicon Motion. Silicon Motion has been somewhat late to the PCIe Gen5 SSD party, as its rival Phison has been offering their high-end PS5026-E26 controller for almost 18 months now. But as Silicon Motion gets ready to make the transition to PCIe 5.0, the company has a trump card up its sleeve: the SM2508 controller, an energy-efficient high-end SSD controller that is intended for lower-power drives.

A PCIe Gen5 x4 controller, SMI’s SM2508 boasts a very low active power consumption of 3.5W. Which, installed in an M.2 SSD, is intended to allow drive manufacturers to built 7 Watt (or lower) SSDs, according to the company. The SM2508 is made on TSMC’s N6 process technology, which is a 7nm-class fabrication node with an optical shrink, which will make it one of the (if not the) most advanced controllers on the market once it ships. The relatively sophisticated node allows Silicon Motion to pack more cores and more features into its controller while keeping its power consumption in check – not to mention the chip size.

Silicon Motion NVMe Client SSD Controller Comparison

 
SM2508
SM2264
SM2268XT2
SM2269XT

Market Segment
High-End
Mainstream

Manufacturing Process
6nm
12nm
12nm
12nm

CPU Cores
4x Cortex R8
4x Cortex R8
2x Cortex R8
2x Cortex R8

Error Correction
4K+ LDPC
4K LDPC
4K+ LDPC
4K LDPC

DRAM
DDR4, LPDDR4X
DDR4, LPDDR4X
No
No

Host Interface
PCIe 5.0 x4
PCIe 4.0 x4
PCIe 4.0 x4
PCIe 4.0 x4

NVMe Version
NVMe 2.0
NVMe 1.4
NVMe 2.0
NVMe 1.4

NAND Channels, Interface Speed
8 ch,
3600 MT/s
8 ch,
1600 MT/s
4 ch,
3600 MT/s
4 ch,
1600 MT/s

Sequential Read
14.5 GB/s
7.5 GB/s
7.4 GB/s
5.1 GB/s

Sequential Write
14 GB/s
7 GB/s
6.7 GB/s
4.8 GB/s

4KB Random Read IOPS
2500k
1300k
1200k
900k

4KB Random Write IOPS
2500k
1200k
1200k
900k

Under the hood, the front-end of the SM2508 SSD controller is based around four Arm Cortex-R8 cores, which will make it a notably powerful controller (Phison’s E26, for reference, is two Arm Cortex R5 cores with an accelerator). This controller is meant to be used with DRAM, as well, and will support both DDR4 and LPDDR4.

The back-end of the chip offers eight NAND channels with 32 CE targets, supporting interface speeds up to 3600 MT/s. Altogether, SMI says that the controller can hit sequential read speeds of up to 14.5GB/sec and write speeds of up to 14 GB/s, while 4K random read and write performance will reach up to 2.5 million IOPS. And SMI’s demo drive at Computex did even better than that, achieving a 14.9GB/sec read speed under CrystalDiskMark.

Silicon Motion and its partners are currently finalizing the firmware for the SM2508 and qualifying it with various manufacturers’ TLC NAND. The chip also supports QLC NAND, though we’d be surprised to see anyone pair such a powerful controller with slower NAND so soon.

At Computex, Silicon Motion itself demonstrated an SM2508 drive in action at its booth. Various drive manufacturers also had SM2508-based drives on the floor as well, though only as static samples.

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