Bit slicing

A bit slice was in the 1970s to the 1980s, a pre-fabricated building block in the form of an integrated circuit, which was used in microelectronics for individual construction of a processor. Bit -slicing called a method from the computer architecture in which one of several different elements that often all for relatively small words -. The bit slices - (usually 4 bits long ) were designed, larger arithmetic units zusammenbaute Bit slices for arithmetic logic unit, registers, and jump and branch units have been combined to achieve the desired word length of the processor. There were also storage for the microprogram, which usually consisted of fast ROM blocks, a microprogram control unit as well as various smaller components such as bus drivers.

Bit-slice components were an evolutionary step on the way from built from individual transistors to computer today exclusively used microprocessor, so the processor on a single chip. In the 1970s and 1980s, bit-slice microprocessor existed for a long time and parallel to each other, since the bit-slice chips were superior to the microprocessors yet. The first microprocessors offered only word lengths of 4 or 8 bits; contrast with bit-slice 16 and 32 -bit processors have been built or even unusual word lengths such as 24 -bit and high performance 64-bit processors.

Increasing integration density allowed both the microprocessors as well as the bit-slices higher performance, so that soon stood microprocessors with 32-bit available and also the bit-slices with 32 bits on a single chip, the result of higher clock speeds and more complex processing units for the time being the microprocessor yet were superior.

In the second half of the 1980s it was possible to integrate the entire CPU for a mainframe computer on a single chip, and the distribution to several components set the clock frequencies increasingly limits that could be outbid by processors on a single chip. The higher development and production costs for processors of bit slices now brought no performance advantage. Prevent loss of the bit slices in general computer firms their right to exist and existed only for a certain time in special applications.

A bit-slice family is to be understood as a modular system for processors, except that higher computer architecture and electronics skills forward as the use of a finished microprocessor block. This, however, plays a minor role, considering that almost every conceivable processor can be implemented using bit-slice components. This advantage has been widely used to build a low-cost prototype of a microprocessor which easily - for example, by changing the microprogram - test, modify and can be corrected. Another field was copying old processor architectures in order to miniaturization or replacement.

With the advent of programmable logic blocks that were complex enough to accommodate full processors (or at least large portions, spread over several blocks), disappeared bit-slice blocks in the late 1980s gradually from the market. Programmable logic devices are flexible, and some types can be also completely reprogram if they are already installed in a circuit.

Examples of bit-slices are the Am2900 family of AMD or the Series 3000 family of Intel.