Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Path: utzoo!decvax!decwrl!glacier!mips!kim From: kim@mips.UUCP Newsgroups: net.micro.pc Subject: Re: 8088-2 Message-ID: <546@mips.UUCP> Date: Sun, 6-Jul-86 21:12:45 EDT Article-I.D.: mips.546 Posted: Sun Jul 6 21:12:45 1986 Date-Received: Mon, 7-Jul-86 17:36:23 EDT References: <3842@utah-cs.UUCP> <205@hscfvax.UUCP> Distribution: na Organization: MIPS ... where RISC is a way of life Lines: 75 >In article <3842@utah-cs.UUCP>, halff@utah-cs.UUCP (Henry M. Halff) writes: >> Several clones advertise that they use a 8088-2 processor. Can >> anyone tell me what the difference is between an 8088-2 and an >> 8088 is? >> >An "8088-2" includes functions/circuits that an 8088-based machine requires a >additional (support) chips for. While an 8088-2 -based machine also requires >support chips, the overall logic chip count is reduced substantially - thereby >reducing cost, size, and (usually) failure points. > g. pavlov, fstrf, amherst, ny. Hold on, there! The 8088-2 part is functionally the same as the 8088. It is spec'd to run at up to 8 MHz, whereas the 8088 is only spec'd to run up to 5 MHz. G. Pavlov's reply sounds like s/he was describing the 80188 part, which does indeed pull alot of the required outboard support logic onto the chip (clock gen, timers, rupt controller, DMA, etc). The 80188 also provides a *few* additional instructions (push-all/pop-all, variable length shifts, etc). The clones that Mr. Halff refers to likely run at 8 MHz, though they probably have a switch or mode in which they run at 4.77 MHz (necessary for *true* compatibility with brain-damaged s/w that uses s/w timing-loops). To anticipate a probable question ... yes, you can replace an 8088 with an 8088-2, *BUT* it will not increase the performance of your system, as the processor will still be clocked at the 4.77 MHz rate (for a true PClone). Increasing the clock on a PClone is an "iffy" proposition, as the rest of the system was probably not designed for higher speed operation. A very reasonable way to boost vanilla PClone performance a bit (10-15%, overall), is to replace the 8088 with a NEC V20 processor. While the clock will still be 4.77 MHz, the NEC chip performs many operations in fewer cycles than does the 8088. As a bonus, the V20 includes the additional instructions that the 80188 has, plus it includes several "new" instructions that provide bit operations, packed decimal arithmetic, and a few others. The V20 also has an "emulation- mode" for the 8080 uP instruction set, and can execute 8080 code directly (of course appropriate control and dispatch s/w is needed to use this in a system). There is an EXCELLENT two-part article on the V20 (and the V30, which is the 8086 replacement) in the Nov/Dec '85 and Jan/Feb '86 issues of "Micro/Systems Journal" if anyone is looking for more information. Currently, V20's go for about $20 (look at the ads in the back pages of BYTE), though I've seen them locally for around $15. As a suggestion, if you plan to make this upgrade, try to get the 8 MHz version of the V20 (even if it will only be run at 4.77 MHz); it seems that there *is* a slight difference in the spec for the clock duty-cycle that *could* cause a problem (erratic operation, etc.) if the 5 MHz part is used (the NEC part-numbers for the 8 MHz parts are: uPD70108C-8 and uPD70108D-8 for plastic and ceramic packages, respectively). Only problem I've had using a V30 in place of an 8086 is a couple of programs that use those brain-damaged s/w timing-loops I mentioned earlier. Gurrrr!!! Disclaimer: I don't work for (or have any connection with) Intel, NEC, BYTE, or Micro/Systems Journal in any way except that I've used their chips and read both magazines. I *do* think that $15-$20 for a 10%-15% performance boost on a 8086/8088 based machine is one of the best values around today. /kim -- UUCP: {decvax,ucbvax,ihnp4}!decwrl!mips!kim DDD: 408-720-1700 x231 USPS: MIPS Computer Systems Inc, 930 E. Arques Av, Sunnyvale, CA 94086 CIS: 76535,25