Conversion from Megabits per second to Gibioctets per second

Information about the Megabit per second (Mbit/s)

The megabit per second is a unit of data transfer rate equal to one million bits per second. Its symbol is Mbit/s, often written Mbps. It is the unit in which internet connections are sold, which makes it the data unit most people encounter by name.

Because it is a decimal million and not 1,048,576, the conversion to octets is exact and easy: one megabit per second is 125 kilooctets per second, so a hundred-megabit connection delivers about 12.5 megaoctets per second at best. Anyone who watches a file transfer and does the division has understood the entire relationship between how connections are advertised and how transfers are reported.

What a household actually needs is far below what it usually buys. Standard-definition video streaming uses about 3 megabits per second, high definition about 5, and ultra-high definition about 25. A video call is around 3 to 8. A large family watching four separate high-definition streams while somebody downloads a game is using perhaps 60 megabits per second, which a hundred-megabit connection handles comfortably.

The reason to buy more capacity than that is not peak speed but behaviour under load. A link that is near its limit develops queues, and queues add delay, which shows up as stutter in video calls and lag in games. A connection with generous headroom keeps its latency low, and that is a more noticeable improvement than a higher number on a speed test.

Wired local networks pass through this range on the way up. The original Ethernet ran at 10 megabits per second, its successor at 100, and both were the standard office connection for a decade each before gigabit replaced them. Wireless standards followed the same path with a lag, and both are now measured in hundreds of megabits or in gigabits.

Real throughput is always below the nominal rate. Protocol overhead takes 5 to 10 per cent on a wired link; a shared wireless channel loses much more, because the medium is divided between all the devices using it and interference forces retransmission. A connection advertised at 100 megabits per second measured at 90 over cable and 50 over a busy wireless network is behaving normally.

One megabit per second equals 1,000,000 bits per second, 125 kilooctets per second, or about 0.9537 mebibits per second.

Information about the Gibioctet per second (Gio/s)

The gibioctet per second is a unit of data transfer rate equal to 1,073,741,824 octets per second, which is 1,024 mebioctets per second. Its symbol is Gio/s. It is the unit of memory bandwidth and of the fastest storage interfaces, and the binary counterpart of the gigaoctet per second, from which it differs by 7.4 per cent.

Memory is where the unit belongs most naturally. A memory channel transfers a fixed number of octets per clock cycle, and that number is a power of two, so the resulting bandwidth is a binary multiple of the clock frequency. A machine with several channels reaches tens of gibioctets per second, and an accelerator with stacked memory reaches thousands.

Storage has caught up. A fast solid-state drive on the current interface sustains several gibioctets per second, which means that for the first time the drive and the memory are within an order of magnitude of each other. That convergence has changed how software is written: the old assumption that reading from disc is thousands of times slower than reading from memory no longer holds.

The unit appears in benchmark output, in system monitoring displays and in the specifications of processor interconnects. All of these count in binary because the structures they measure are binary, and reporting the result with a decimal prefix would introduce a seven per cent error for the sake of a familiar-looking label.

For a sense of what the rate means, one gibioctet per second copies a two-gigaoctet film in under two seconds and fills a one-teraoctet drive in about a quarter of an hour. Anything at this speed is faster than every external connection in an ordinary building, so the limiting factor moves inside the machine.

The distinction from the decimal unit matters most in procurement and capacity planning. A specification that requires 10 gigaoctets per second and a system that delivers 10 gibioctets per second are not the same, and the difference of 7.4 per cent is the sort of margin that decides whether a design meets its requirement.

One gibioctet per second equals 1,073,741,824 octets per second, 1,024 mebioctets per second, or about 1.074 gigaoctets per second.