What is a parallel database and explain how it works?

Number of pre-decode bits used

Type/year of first volume shipment	Number of pre-decode bits appended to each instruction
PA 7200 (1995)	5
PA 8000 (1996)	5
PowerPC 620 (1996)	7
UltraSparc (1995)	4
HAL PM1 (1995)	4
AMD K5 (1995)	5
R10000 (1996)	4

For a CISC processor such as the AMD, K5 pre-decoding can determine where an instruction starts or ends, where the opcodes and prefixes are, and so on. This requires quite a large number of extra bits. The K5 adds five extra bits to each byte. Thus, in this case, more than 70% additional storage space is needed in the instruction cache.
Predecoding is used either to shorten the overall cycle time or to reduce the number of cycles needed for decoding and instruction issues. For instance, pre-decoding the PowerPC 620, R10000, and Hal’s PM1 require only a single cycle for decoding and issue.