reynolds@milton.u.washington.edu (Michael Reynolds) (02/20/91)
Aaaarrrrggghhh!!! Has anybody been able to get COM3 to work on a Zenith 386SX without having to disable COM1? I know (or *think* I know) this much: 1) Most, but not all, I/O cards do not allow sharing of IRQs between Com ports. Thus, unless the I/O card says so, I can't, say, configure my add-on com port card for COM3 (03E8h) and have it share IRQ 4 with Com1. I've read this in one place, and it seems to be my experience. On my Zenith 386SXs, I can use COM3 no problem with IRQ4, but only if I disable COM1 in the monitor program. 2) If your I/O card allows use of other IRQ levels for you Com ports, and if you can get your software to look for them at non-standard IRQ levels, you *can* use Com3 on your PC simultaneous with Com1. For instance, on my Zenith 386/16 (a full 386, not an SX), I've hacked the Windows mouse driver to look for the mouse at Com3 at IRQ level 5, configured my add-in I/O card to suite, and been able to use the mouse on Com3, leaving Com1 and Com2 useable to Windows for communications or whatever. Someone tell me if I'm mistaken in my understanding of the above. Now, the problem is that I CAN'T GET A ZENITH 386SX TO RECOGNIZE COM3. I did the hack described above in #2, and also a hack for a regular DOS mouse driver, both of which worked great on my 386/16. But neither works on a 386SX!! In fact, if I even PLUG IN my Com3 card, even when configured for IRQ5, not only does the 386SX not recognize Com3, it doesn't even recognize Com1 any more!! Aaarrgghh! My suspicion is that the 386SX does something tricky with the Com port stuff, maybe on the BIOS level, that screws up my work-arounds. Mostly, what makes me suspicious, besides the fact that it doesn't work, is that the Com ports are enabled and disabled from the monitor program, instead of from jumpers. I really hated the 386SX 16MHz models when they came out--they were obviously rushed into production before being debugged--so I stayed away from them. Now, due to price pressure, I've started buying the 20MHz 386SX models, hoping that by now all the bugs have been worked out. If I can't figure this out, though, I might switch to a no-name clone--at least they don't try to be tricky-dicks with the Com ports. I would really appreciate any comments/help/observations that might help me with this problem or help me decide whether to keep buying these Zenith 386SXs or not. Thanks much. Michael Reynolds Libraries Micro Services U of Washington, Seattle Internet: reynolds@milton.u.washington.edu Phone: (206) 543-9237