Hardware speeds are shifting

Hardware speeds are shifting

May 30, 2024

The dominant speeds of hardware components are shifting.

Current #

Memory #

DDR4 3200MT/s where MT/s measures the number of data transfers per second. Each transfer in DDR memory typically involves 64 bits (8 bytes) of data.

So the bandwidth in GB/s is: 3200 MT/s × 8 bytes/transfer=25600 MB/s, i.e., 25600 MB/s÷1024 = 25 GB/s

PCIe #

PCIe Gen 4x16 which provides a data transfer rate of 16 GT/s (Giga Transfers per second) per lane.

With 16 lanes, this results in a total bandwidth of 256 GT/s.

Calculate the bandwidth in GB/s with Throughput/Bandwidth = Transfer rate * Encoding scheme,

The PCIe Gen 4 uses a 128b/130b encoding schema, Which means that 130 bits must be sent for every 128 bits transmitted. The two extra bits are not meaningful information for the upper layer.

Then, each Lane of the PCIe 4 protocol supports a rate of 16 * 128/130 = 16 Gbps = 2 GB/s, with a total of 16 lanes, we have 2 GB/s * 16 = 32 GB/s.

Ethernet #

400G Ethernet which provides 400Gps / 8 = 50 GB/s

PCIe 4.0 NVMe SSDs #

Take the Samsung 990 Pro as an example,

  • Sequential Read: 7459 MB/s
  • Sequential Write: 6900 MB/s
  • Random Read: 1600K IOPS
  • Random Write: 1550K IOPS

Current dominant figures in data center #

  • DDR4 3200MT/s ~ 25 GB/s
  • PCIe Gen 4*16 ~ 32 GB/s
  • 400G ethernet ~ 50 GB/s
  • PCIe 4.0 NVMe SSD ~ 7.5 GB/s read, 7 GB/s write

The shifting #

  • DDR5 4800MT/s ~ 38GB/s
  • PCIe Gen 5x16 ~ 64 GB/s(still uses 128b/130b encoding schema)
  • 800G ethernet ~ 100 GB/s
  • PCIe 5.0 NVMe SSD ~ 14 GB/s read, 13 GB/s write

Reference #