Conversion from Gigaoctets per second to Gibioctets per second

Information about the Gigaoctet per second (Go/s)

The gigaoctet per second is a unit of data transfer rate equal to one thousand million octets per second, or eight gigabits per second. Its symbol is Go/s. It is the unit of the fastest storage devices and of the buses inside a computer, where data moves between processor, memory and drive.

Solid-state drives on the current interface reach 3 to 14 gigaoctets per second, depending on the number of lanes they use and the generation of the bus. Each lane of the peripheral interconnect provides roughly 2 gigaoctets per second at the current generation, and a drive typically uses four of them. Doubling the generation doubles the rate, which is why the figures have risen so steadily.

Main memory is faster still. A modern memory channel delivers 30 to 60 gigaoctets per second, and a machine with several channels reaches hundreds. Graphics processors, which must feed thousands of arithmetic units at once, use memory with bandwidths measured in thousands of gigaoctets per second, at which point the unit gives way to teraoctets.

That hierarchy is what determines how a program performs. A processor can execute far more operations per second than memory can supply data for, so most fast software is written to keep data in the small fast caches rather than to fetch it repeatedly from main memory. The whole discipline of performance engineering rests on the size of these differences.

For everyday comparison, one gigaoctet per second copies a two-gigaoctet film in two seconds, and fills a one-teraoctet drive in about seventeen minutes. That is faster than the network in almost every home and faster than most external connections, so at this rate the bottleneck moves back to whatever is at the other end.

The unit also describes network links in the data centre. A ten-gigabit connection is 1.25 gigaoctets per second, a hundred-gigabit connection 12.5, and both are common between servers. Comparing a storage figure in octets with a network figure in bits requires the factor of eight, and forgetting it is how equipment gets mismatched.

One gigaoctet per second equals 1,000,000,000 octets per second, 8 gigabits per second, or about 0.9313 gibioctets 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.