Path: utzoo!attcan!uunet!husc6!mailrus!ames!nrl-cmf!cmcl2!rutgers!ucla-cs!wales From: wales@valeria.cs.ucla.edu Newsgroups: comp.sys.ibm.pc Subject: 286-based accelerator boards -- followup Summary: Not really what they're cracked up to be Message-ID: <14742@shemp.CS.UCLA.EDU> Date: 26 Jul 88 20:54:45 GMT Sender: news@CS.UCLA.EDU Reply-To: wales@CS.UCLA.EDU (Rich Wales) Organization: UCLA Computer Science Department Lines: 79 A while back, I asked for comments on 286-based accelerator boards for PC's or XT's (or clones thereof). I have a Taiwanese turbo XT clone (8-MHz NEC V-20, 8/4.77 MHz clock, 0 wait states). The RAM is a mix of 120-ns and 150-ns chips; yes, I know that 150-ns chips should theoret- ically not work at 8 MHz with 0 wait states, but apparently the toler- ances on these chips are such that they do work quite reliably (at least, I've never had any problems, and I run *everything* at 8 MHz). The "turbo board" market appears to be a lot less clear-cut and satis- fying than I had initially supposed. Several people (including people on the net, as well as several computer dealers) advised me against this route -- saying that they had seen many, many times when these boards simply didn't work right -- and even when they did, the speedups in actual practice were not nearly as dramatic as one might hope for, since you're still stuck with the 8-bit bus of the original system. I had initially been attracted to the Orchid "Tiny Turbo 286" acceler- ator board. But a call to Orchid's technical support dampened this idea -- they told me in no uncertain terms that the Tiny Turbo 286 DEFINITELY WOULD NOT WORK in a turbo clone built around an 8-MHz processor, EVEN if the clock were always run at 4.77 MHz. I couldn't get any comprehensi- ble explanation of why; they just said it wouldn't work and wasn't worth even trying, period. Orchid does have a faster turbo board, as does AST -- but in either case I would very probably have to replace all my RAM with 100-ns or faster (a sizable expense nowadays). I also looked into the idea of upgrading to a 286-based motherboard. AST, for instance, has one called "Xformer/286" ("X" pronounced "trans") that runs at 10 MHz with 0 wait states. It has 512K of RAM on the board and can take either 128K or 512K of additional chips. Of course, these chips had better be 100-ns (at least, AST was unwilling to recommend the use of slower chips -- not surprising, considering the clock speed and the 0 wait states). The AST Xformer/286 is said to be exactly the same size as the standard XT motherboard (except for a little extension on the front), and is supposed to fit in the standard XT cabinet. (My clone's motherboard and cabinet are the standard XT size. Note that the AST Xformer/286 is known *not* to be suitable for some clones; the AST people mentioned the Tandy 1200, Leading Edge Model D, Compaq Deskpro, AT&T 6300, and Epson Equity II in their "don't waste your time" list.) After considering the idea for some time, though, I have decided not to try to upgrade my present system. I've already indicated my less-than- positive conclusions regarding accelerator boards. As for swapping the motherboard, four factors tend to make me decide against it: (1) I would probably have to upgrade my current power supply (which is rated at about 140 W) to a 200-W supply. One dealer suggested that I *might* be able to get away with my current supply after all, but I'm not sure I'm prepared to take that gamble. (2) I would probably have to buy a load of 100-ns RAM chips -- though I could save some money by expanding the 512K on the AST motherboard with just 128K extra (i.e., 64K chips instead of 256K). (3) I would probably have to get a new video board. My current board (a Taiwanese Hercules clone) has 150-ns RAM chips; while it works OK at 8 MHz (see above comment on lax timing tolerances in RAM chips), I would consider it unlikely to work at 10 MHz. (Then again, are video boards set up to use extra wait states to the video RAM, inde- pendently of the wait states the CPU may or may not be using for the regular RAM?) I do plan to upgrade my video stuff eventually, but I don't really want to do so *now*. (4) I'm not sure how much of a speedup (if indeed any at all) I could expect to get from my hard disk card, since it would still use only the 8-bit XT bus connections. And I'm not really of a mind to buy a new hard disk card specifically designed for an AT bus. In conclusion, I suspect that upgrading my system with a new motherboard would likely end up costing almost as much as a new system -- and that I'd be better off just waiting until I can afford to trade in my whole system for a "real" AT clone. Comments, anyone? -- Rich Wales // UCLA Computer Science Department // +1 (213) 825-5683 3531 Boelter Hall // Los Angeles, California 90024-1596 // USA wales@CS.UCLA.EDU ...!(uunet,ucbvax,rutgers)!cs.ucla.edu!wales "Spiff's hyper-freem drive malfunctions! The aliens close in!"