Talk:Intel 8051

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[edit] 8051 architecture

Is 8051 a CISC or RISC machine? Is 8051 a Harvard architecture? —The preceding unsigned comment was added by 61.17.44.86 (talk) 08:05, 29 January 2007 (UTC).

The 8051 is defintiely a CISC machine. It's instruction set is wide and varied with lots of addressing modes and only a few registers. RISC machines typically have a much smaller instruction set and a bank of 16 or 32 registers. RISC machines typically only operate on data in the registers and have a "load/store" architecture. The 8051 instruction set mostly operates on the Accumulator and values in memory. Thus, the 8051 is CISC.

The 8051 is considered a Harvard Architecture machine because it has separate code and data spaces. Depending on the implementation however, it can be either Harvard or von-neumann. Older versions of the 8051 are more often van-neumann in that the CPU takes several clock cycles to fetch each operand/instruction individually. Newer single-cycle 8051s are often Harvard so they can get higher performance. The Harvard architecture allows the Instruction and the operands to be fetched in the same cycle. 68.189.241.68 (talk) 14:28, 24 February 2008 (UTC)