Megabyte per second to Gigabyte per second

Many USB drives use a small SLC cache for initial writes at high MB/s, then slow dramatically once the cache fills and data writes to slower TLC/QLC NAND. A drive that starts at 200 MB/s might drop to 20–30 MB/s after the first few gigabytes. Check sustained write speed reviews, not just peak numbers.

Editing 4K ProRes footage requires about 200–400 MB/s of sustained read speed. 8K RAW can demand 1,000+ MB/s. A SATA SSD (550 MB/s) handles 4K fine, but 8K workflows really need NVMe drives at 3,000+ MB/s. The timeline scrubbing experience directly correlates with MB/s.

Look at the capitalisation: lowercase "b" (Mbps) means megabits, uppercase "B" (MB/s) means megabytes. Most speed test websites (Speedtest by Ookla, fast.com) default to Mbps. If your result seems 8× lower than expected, you are probably reading MB/s where you expected Mbps.

PCIe 5.0 NVMe SSDs hit 12,000–14,000 MB/s sequential read speeds. That is fast enough to load an entire 50 GB game in about 4 seconds. PCIe 6.0 drives, expected soon, will double this again to roughly 25,000 MB/s.

Network transfers add latency, protocol overhead (SMB, NFS), and are limited by the network link speed. A file on a local NVMe SSD reads at 7,000 MB/s, but sharing it over a 1 Gbps network caps throughput at 125 MB/s. Even 10 GbE only gives 1,250 MB/s — a fraction of modern SSD capability.

CPUs constantly shuttle data between RAM and their caches. DDR5-6000 provides about 96 GB/s of bandwidth in dual-channel mode. In games, insufficient RAM bandwidth causes frame drops during complex scenes. In productivity tasks like video encoding, it directly limits how fast the CPU can process data.

Thunderbolt 4 runs at 40 Gbps, which is 5 GB/s. Thunderbolt 5, released in 2024, doubles this to 80 Gbps (10 GB/s) with a burst mode up to 120 Gbps (15 GB/s). This is fast enough to run an external NVMe SSD at near-internal speeds.

Both, depending on generation. A PCIe 3.0 ×4 interface caps at ~3.5 GB/s, bottlenecking modern NAND. PCIe 4.0 ×4 raises this to ~7 GB/s, and PCIe 5.0 ×4 to ~14 GB/s. The drive's NAND flash and controller also have limits — the fastest SSDs and the fastest interfaces are in a constant leapfrog.

GPUs use wide memory buses (256–384 bits) with very fast HBM or GDDR6X memory running at high clock speeds. An RTX 4090 has a 384-bit bus with GDDR6X at 21 Gbps per pin, totalling 1,008 GB/s. HBM3 in data center GPUs achieves 3,000+ GB/s through stacked memory with 4096-bit buses.

At multi-GB/s rates, CPU processing speed, software efficiency, and thermal throttling become bottlenecks. A 14 GB/s PCIe 5.0 SSD can deliver data faster than most applications can consume it. Decompression, parsing, and memory allocation in software often cannot keep up with raw storage bandwidth.