Conversion from 5 Bits per second to Gibibits per second

Information about the Bit per second (bit/s)

The bit per second is the fundamental unit of data transfer rate. Its symbol is bit/s, often written bps. It counts how many binary decisions a channel carries in one second, and every other unit of transmission speed is a multiple of it.

Because it is a rate, it has the form of a quantity divided by time, exactly like metres per second or litres per second. That makes the arithmetic straightforward: a link running at a given number of bits per second, multiplied by a duration in seconds, gives the total number of bits transferred, and dividing by eight converts that to octets.

The unit must be distinguished from the baud, which counts symbols per second rather than bits. Early modems transmitted one bit per symbol, so the two numbers were the same and the words were used interchangeably. Modern schemes encode several bits in each symbol — by varying phase and amplitude together — so a channel running at 3,000 baud may carry 33,600 bits per second. Only the bit rate describes how much information moves.

Claude Shannon established the theoretical ceiling in 1948. The capacity of a channel in bits per second depends on its bandwidth and on the ratio of signal to noise, and no coding scheme can exceed it. Every advance in modem and radio design since has been an attempt to approach that limit more closely, and modern systems come within a fraction of a decibel of it.

In practice the raw bit rate of a link is never the rate at which useful data arrives. Protocol headers, error-correcting codes, acknowledgements and retransmissions all consume capacity, and the usable fraction is typically 90 to 95 per cent on a wired link and considerably less on a shared wireless one.

Single bits per second are rarely quoted, because almost every channel is faster. The exceptions are deep-space communication, where a probe billions of kilometres away may return data at a few tens of bits per second, and certain low-power sensor networks that transmit a handful of bits at long intervals to preserve battery life.

One bit per second equals 0.125 octets per second, 0.001 kilobits per second, or about 0.0009766 kibibits per second.

Information about the Gibibit per second (Gibit/s)

The gibibit per second is a unit of data transfer rate equal to 1,073,741,824 bits per second. Its symbol is Gibit/s. It is the binary counterpart of the gigabit per second, and the two now differ by 7.4 per cent, which is enough to matter in any engineering specification.

The unit belongs to the inside of a machine rather than to the network. Memory buses, processor interconnects and the links between chips on the same board all move a power-of-two number of bits per clock cycle, so their throughput is naturally expressed with a binary prefix. A bus sixty-four bits wide clocked at a given frequency delivers a rate that is a binary multiple of that frequency.

Networking, by contrast, is decimal all the way down. Gigabit Ethernet carries exactly one thousand million bits per second, not 1,073,741,824, and the symbol rate on the wire is chosen to make that so. Confusing the two overstates a link's capacity by seven per cent, which in a capacity plan is the difference between adequate and insufficient.

In octets a gibibit per second is 134,217,728, or 128 mebioctets per second. That is close to the throughput of a fast mechanical hard drive and well below a modern solid-state drive, so it sits at the point where storage and internal buses meet and where matching their rates becomes a design question.

Benchmark tools are the commonest place to see the unit written correctly. A memory bandwidth test that allocates buffers in powers of two and measures how long they take to traverse naturally reports in gibibits or gibioctets per second, and a well-written tool says so explicitly rather than rounding to the decimal unit.

The reason to insist on the distinction here rather than lower down the scale is arithmetic. At the kibibit the gap was 2.4 per cent and could be ignored; here it is nearly a thirteenth, and it grows by a further 2.4 per cent at every step above. Getting into the habit at this level costs nothing and avoids compounding errors later.

One gibibit per second equals 1,073,741,824 bits per second, 134,217,728 octets per second, or about 1.074 gigabits per second.