jojo@speedy.WISC.EDU (Jon Wesener) (08/25/87)
I have recently been hearing how AMD 16Mhz 80286-16 with CHIPS chips set is faster than the 80386 also running at 16Mhz. Does this rumor take into consideration the different I/O Bandwidths? It would seem the 286 would still have 1/2 the bandwidth which would affect everything from memory to disk access times. Does anyone know? --j jon wesener jojo@speedy.wisc.edu "If you like ASTROTIT, you should see what's coming! ;-)"
toma@tekgvs.TEK.COM (Tom Almy) (08/27/87)
In article <4149@spool.wisc.edu.WISC.EDU> jojo@speedy.WISC.EDU (Jon Wesener) writes: > >I have recently been hearing how AMD 16Mhz 80286-16 with CHIPS chips >set is faster than the 80386 also running at 16Mhz. [...] >It would seem the 286 would still have 1/2 the bandwidth Well it depends on the benchmark program. Most instructions will execute in the same number of clocks on both processors. If the AMD system has 0 wait states it could easily run many benchmark programs faster than an 80386 system with one wait state. To tip the scale in favor of the 80386 you can execute benchmarks with lots of fast executing but multi-byte long instructions which would show the advantage of the 80386 instruction queue. Benchmark the performance of VDISK -- the extended (or is it expanded?) memory fetches are done by moving 32 bits at a time instead of 16, and the return to real mode is done without reseting the processor -- VDISK is much faster. To really see the speed advantage you will need to run benchmark programs with different machine code for the 80386. For instance, the famous 8086 killer C benchmark "long i; for (i=0; i<1000000; i++);" will be much faster on the 80386 because of the 32 bit data registers and instructions. "Large Model" programs can be recompiled small model on the 80386, saving lots of execution time, because of the 4 gigabyte segment size. Now the rest of the system (disks, display, in fact anything plugged into the PC bus) will not be any faster with an 80386 because the data path is a mere 16 bits wide. I have found that EGA intensive programs do not run noticibly faster on the 80386 than they did on my older 8Mhz PC/AT. An 80386 system could be real nice if it didn't have to be PC/AT compatible. Tom Almy toma@tekgvs.TEK.COM {many hubs}!tektronix!tekgvs!toma
ching@amd.AMD.COM (Mike Ching) (08/27/87)
In article <4149@spool.wisc.edu.WISC.EDU> jojo@speedy.WISC.EDU (Jon Wesener) writes: > > I have recently been hearing how AMD 16Mhz 80286-16 with CHIPS chips > set is faster than the 80386 also running at 16Mhz. Does this rumor > take into consideration the different I/O Bandwidths? It would seem > the 286 would still have 1/2 the bandwidth which would affect everything > from memory to disk access times. Does anyone know? > >--j >jon wesener >jojo@speedy.wisc.edu > "If you like ASTROTIT, you should see what's coming! ;-)" The rumor is an exaggeration. The comparison was a PC-Limited 286 running at 16MHz and a Compaq 386 also running at 16MHz. The performance of the 286 is claimed to be 94% of the 386 running the same code (Dhrystone compiled with Microsoft C). The price/ performance ratio is where the 286 comes out ahead. Memory bandwidth is doubled with the 386 but the I/O is not limited by bus bandwidth in a PC. I'm not a spokesman for the company...just reading off the press release. mike ching
davidsen@steinmetz.steinmetz.UUCP (William E. Davidsen Jr) (08/28/87)
In article <4380@amd.AMD.COM> ching@amd.UUCP (Mike Ching) writes: |In article <4149@spool.wisc.edu.WISC.EDU> jojo@speedy.WISC.EDU (Jon Wesener) writes: |> |> I have recently been hearing how AMD 16Mhz 80286-16 with CHIPS chips |> set is faster than the 80386 also running at 16Mhz. Does this rumor |The rumor is an exaggeration. The comparison was a PC-Limited 286 |running at 16MHz and a Compaq 386 also running at 16MHz. The |performance of the 286 is claimed to be 94% of the 386 running the |same code (Dhrystone compiled with Microsoft C). The price/ |performance ratio is where the 286 comes out ahead. Memory bandwidth |is doubled with the 386 but the I/O is not limited by bus bandwidth |in a PC. As a DOS machine the 286 is probably far more cost effective than the 386. Running software which takes advantage of the 386 would make the 386 more cost effective, but only if you need the power. It's hard to beat the <$1k XT clone including a display and 20mb slow hard disk when it comes to price performance. -- bill davidsen (wedu@ge-crd.arpa) {chinet | philabs | seismo}!steinmetz!crdos1!davidsen "Stupidity, like virtue, is its own reward" -me