dbearly@vax1.tcd.ie (BIG BAD DOM) (11/14/89)
I have been examining a /286 machine recently which runs at a speed of 8 Mhz.Now it seems a bit pointless to me that the faster processor should run at the typical speed of the slower 8088/8086 type machines. Could someone please tell me does a 286 @ 8Mhz run any faster then an 808/86 @ 8MHz ? If so is it not pointless to produce such a machine as the extra price is not justified?? Big Bad Dom. ******************************************************************************** IN%"dbearly@vax1.tcd.ie" IN%"dbearly@unix1.tcd.ie" ********************************************************************************
usenet@cps3xx.UUCP (Usenet file owner) (11/15/89)
In article <3492@vax1.tcd.ie> dbearly@vax1.tcd.ie (BIG BAD DOM) writes: >Could someone please tell me does a 286 @ 8Mhz run any faster then >an 808/86 @ 8MHz ? Of course it does; at least twice as fast. This is because the '286 accesses memory 16 bits at a time (fetch), as opposed to 8 bits at a time (fetch fetch). A '386 (not an sx) will access a full 32 bits at a time (FETCH!), and so if it runs at the same clock rate it will be roughly twice as fast again. Of course, if you take advantage of the enhanced instruction set, you can get even greater speedup. In the rare case that original ideas Kenneth J. Hendrickson N8DGN are found here, I am responsible. Owen W328, E. Lansing, MI 48825 Internet: hendrick@frith.egr.msu.edu UUCP: ...!uunet!frith!hendrick
woan@peyote.cactus.org (Ronald S. Woan) (11/15/89)
The 8 MHz '286 system will run about twice as fast as any of the 8088 based systems at the same clock rate because of its 16 vs. 8-bit datapath. Actually it does a little better for because it executes some instructions in fewer cycles and has a extended instruction set that speeds program execution (given that your application uses '28 instructions). Anyways, the '286 machines cost very little more and are generally worth it for their increased throughput from 16 bit I/O. Ron -- +-----All Views Expressed Are My Own And Are Not Necessarily Shared By------+ +------------------------------My Employer----------------------------------+ + Ronald S. Woan @cs.utexas.edu:ibmaus!auschs!woan.austin.ibm.com!ron + + second choice: woan@peyote.cactus.org +
wirthlin@uvm-gen.UUCP (Ralph Wirthlin,Gamma IV,31415926535,27182818) (11/15/89)
From article <5392@cps3xx.UUCP>, by usenet@cps3xx.UUCP (Usenet file owner): > In article <3492@vax1.tcd.ie> dbearly@vax1.tcd.ie (BIG BAD DOM) writes: >>Could someone please tell me does a 286 @ 8Mhz run any faster then >>an 808/86 @ 8MHz ? > > Of course it does; at least twice as fast. This is because the '286 > accesses memory 16 bits at a time (fetch), as opposed to 8 bits at a > time (fetch fetch). A '386 (not an sx) will access a full 32 bits at a > time (FETCH!), and so if it runs at the same clock rate it will be > roughly twice as fast again. Of course, if you take advantage of the > enhanced instruction set, you can get even greater speedup. An 8086 will also access memory 16 bits at a time on a word boundary (fetch). As someone pointed out, however, the 286 has reduced the number of cycles required for a few of the, previously, expensive instructions such as div or mul. I also believe (don't have the tech manual handy) that the pre-fetch queue on the 286 is larger than the 8086, thus increasing the throughput. The relative speed of the 286 over the 86 is obviously complicated by the type of program being run. Is the program cpu or memory-bound? I believe (again, no manual) that several of the string operations on the 286 use the DMA controller. If so, then a program that makes extensive use of these instructions will run a good deal faster (about 4 times ?????). Conclusion? Well, yes, an 8-Mhz 286 will generally run faster than an 8-Mhz 8086. Relative speed? That depends. Try running norton on both. ( Someone correct me if I made any obvious mistakes :-)). Ralph ------------------------------------------------------------------------------- Ralph L. Wirthlin | "Who knows where madness lies .. Internet:wirthlin@emily.uvm.edu | To surrender dreams, this may be BITNET: R_WIRTHLIN@UVMVAX | madness .. too much sanity is madness, | but maddest of all is to see life as USMAIL: 9B College Parkway | it is and not as it should be" Colchester, VT 05446 | - Man of La Mancha -------------------------------------------------------------------------------
ODX@PSUVM.BITNET (Tim Larson) (11/17/89)
In article <1336@uvm-gen.UUCP>, wirthlin@uvm-gen.UUCP (Ralph Wirthlin,Gamma IV,31415926535,27182818) says: > > > An 8086 will also access memory 16 bits at a time on a word boundary >(fetch). As someone pointed out, however, the 286 has reduced the >number of cycles required for a few of the, previously, expensive >instructions such as div or mul. I also believe (don't have the >tech manual handy) that the pre-fetch queue on the 286 is larger than >the 8086, thus increasing the throughput. > The relative speed of the 286 over the 86 is obviously complicated by >the type of program being run. Is the program cpu or memory-bound? > This is the most important point -- what is your application doing? Word processing, database, program development, etc. are all IO-intensive (most office type programs are). Games, etc. may not be so IO-intensive. The biggest difference, then, is whether you have an 8-bit data bus, 16-bit data bus, or a 32-bit data bus (like MicroChannel or EISA). The 8086 can handle 16 bits of data (unlike the original 8088), but is most often (always?) stuck in an 8-bit XT style bus. The 80286 is most often stuck in a 16-bit AT style bus and thus IO gets a performance boost of roughly 2X. Put an 80286 in an XT and what do you get? Very modest performance improvement at the same clock rate (is this why so-called accelerators have faded into the background?). Recall, too that the AT bus is a superset of the XT bus and XT cards in an AT slot won't do much to improve performance. An AT with all XT cards will not be a lot faster than an XT at the same clock rate. Note that this is the way many *inexpensive* clones stay inexpensive, and the reason that they often are a disappointment to their buyers. Moral: buyer beware! -Tim Larson odx@psuvm.bitnet
msschaa@cs.vu.nl (Schaap MS) (11/17/89)
In article <270@peyote.cactus.org> woan@peyote.cactus.org (Ronald S. Woan) writes: > >The 8 MHz '286 system will run about twice as fast as any of the 8088 >based systems at the same clock rate because of its 16 vs. 8-bit datapath. I have a 8086. Does this mean that it is also twice as fast as a 8088?