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The minicomputers made with bit-slices had 16-bit ALUs or 32-bit ALUs. Those 16-bit or 32-bit ALUs were made from 2-bit, 4-bit or 8-bit slices, but this did not matter for the programmer, and it did not matter even for the micro-programmer who implemented the instruction set architecture by writing microcode. The size of the slices mattered a little for the schematic designer who had to draw the corresponding slices and their interconnections an it mattered a lot for the PCB designer, because each RALU slice (RALU = registers + ALU) was a separate integrated circuit package. Intel made 2-bit RALU slices (the Intel 3000 series), AMD made 4-bit RALU slices (the 2900 series), which were the most successful on the market. There were a few other 4-bit RALU slices, e.g. the faster ECL 10800 series from Motorola, Later, there were a few 8-bit RALU slices, e.g. from Fairchild and from TI, but by that time the monolithic processors became quickly dominant, so the bit-sliced designs were abandoned. The width of the slices mattered for cost, size and power consumption, but it did not matter for the architecture of the processor, because the slices were made to be chained into ALUs of any width that was a multiple of the slice width. |