tim@cit-vax.Caltech.Edu (Timothy L. Kay) (10/25/87)
Here is a problem with an add on board that is baffling even the people who designed the board. They have it on their list of things to do, but maybe somebody out here has an idea what the problem might be. Then I can speed them up. I have an AT clone that switches 6/10 Mhz. The bus speed is always the same as the active CPU speed (as opposed to, say, running at 8 Mhz when the CPU is running at 10 Mhz). Everything works perfectly at 6 Mhz. Their board won't talk at 10 Mhz. This much the manufacturer understands. The wierd part is that, when I have their board plugged into my bus, and I try to run at 10 Mhz, I can't *write* to the hard disk. I can read just fine, and everything else seems to work. If I try to write, the machine hangs. However, I know that interrupts remain enabled, and the O/S remains intact because I am running a TSR clock that puts the time in the upper right of the screen; it keeps running! The hard disk is a standard WDC controller and Seagate 40 Mbyte 38ms avg access time. One last piece of information: the manufacturer has verified the problem by plugging another board into another 6/10 Mhz clone. They see the same symptoms. Any ideas? My guess is that the hard disk driver is waiting for the hard disk to interrupt, and the add-on board is causing it to miss this interrupt. If this were the case, shouldn't disk reads also be affected? Tim