monitor (10/26/82)
There is no defect in the architecture of the 8088. There is a performance loss caused by the 8 bit external bus: all fetches of 16 bit operands will be twice as slow. The 4 byte prefetch buffer is of instructions only. All addresses for operands (and instructions) take two cycles to access. You can expect a 20-40% difference in speed between the two processors. This is why the IBM PC doesn't blow the Apple III, et. al. out of the water, even when running assembly code. (By blowing out of the water, I mean the 8 or 10 to 1 ratio of speed that a 16 bit processor like the 8086 should (and does) give. Pat Wood whuxg!phw
monitor (10/27/82)
Sorry...the address bus on the 8088 is 20 bits wide and takes only one cycle to put the address out to the memory controller. As for the performance differences, they are dependent (of course) on application. Compute bound programs will run almost as fast on the 8088 as on the 8086; programs that perform a lot of memory accesses (for 16 bit data, e.g., pointer manipulation) will run much slower. Pat Wood whuxk!monitor whuxg!mphw