A performance evaluation of the Intel 80286

In the last issue of CAN we published a performance comparison of the Intel iAPX-432, Intel 8086, Motorola 68000, and DEC VAX-11/780.~ We mentioned that Intel had announced a successor to the 8086, called the 80286. ]ntel is sampling parts now and will ship 8 MHz and 10 MHz versions next winter. In addition to new instructions that support 32-bit data, the 286 has a sophisticated protection mechanism reminiscent of MULTICS. The 286 also has a compatibility mode to run existing 8086 programs. Tom Conroy, a Berkeley student, spent the summer working for Intel and measured the performance of the 286 on the same four programs used in the previous study. Conroy ran these programs on a n actual 286 using a logic analyzer to count the number of clocks for each program. This breadboard has hmited ]/0 thus the write statements were removed from program-this will have little effect on performance as there is almost no I/0. Since the 286 Pascal compiler was not available, the programs were run in 8086 compatibility mode. The three critical performance tables have been reproduced from the original report with new lines at the bottom for the 286. The first two tables show the execution times and performance relative to a VAX-11/780 running VMS Pascal. Table 3 shows the performance of the microprocessors assuming an 8 MHz clock. This last table was the basis of one of the few critical comments that we have received on the previous paper: "YotL can't possibly get an adequate a77Lount of no ~a~ state 77~e77~OTy in a ~,icToprocessov systeTn. I n c l u s i o n of those tittles ~ ~'i, sleadi~g. " Sun Microsystems Inc. in Silicon Valley supplies an excellent counterexample. They are selling a 10-MHz 68000 system without wait states for up to 1.75 mega-bytes-including memory mangement and parity on bytes. The b o t t o m performance line as measured by these four small programs is that the newest version of the 432 (8 MHz with 4 wait states) is almost as fast as a 5 MHz 8086, while the 80286 leads the 432 by almost an order of magnitude. Furthermore, this fast machine (in 8086 compatibility mode) outperforms a 16-MHz 68000. T "A Performance Evaluation of the Intel iAPX 432,"