Path: utzoo!attcan!uunet!wuarchive!brutus.cs.uiuc.edu!ux1.cso.uiuc.edu!iuvax!maytag!focsys!larry From: larry@focsys.uucp (Larry Williamson) Newsgroups: comp.unix.i386 Subject: Tuning aha1540 driver (ISC 2.2) Message-ID: Date: 15 Aug 90 17:51:07 GMT Sender: larry@focsys.uucp (Larry Williamson) Organization: Focus Automation Systems Inc. Waterloo, Ontario. Lines: 39 A few weeks back (late june, I think) there was a thread here on tuning the scsi driver for ISC Unix 2.2. I saved most of those articles since we were planning on installing 1542A's on some machines here. I'm doing that now. My tests seem to indicate that the default values for BUSON, BUSOFF and DMASPEED are the fastest. I've installed the Sync option jumper on the controller. With BUSON 5, BUSOFF 9 and DMASPEED 0; the system seems to be performing just fine. I'm not entirely sure how to modify the DMASPEED parameter. Values of 0 and 1 seem to work, but 2 causes the system to enter the kernel debugger at boot time. I've not bothered trying a value of 3. How do these values relate to the DMA speeds of 5, 5.7, 6.7 and 8 Mhz that the controller is supposed to be able to support? Is it the obvious 0->5, 1->5.7, 2->6.7, 3->8? The test bed system I'm using is an AMI MB with 4 Meg ram, 64K cache and 20 Mhz clock. I'm bothered that if I modify these values in /etc/conf/cf.d/[ms]tune, I get compiler warnings about these values being redefined. So I've been modifying them in /usr/include/sys. I don't like this. What is the normally accepted practice? Ignore the warnings? I hope not. During these tests I've left the DMA speed selection header on the board open. This selects the default of 5 Mhz. I'm going to try other selections on the jumpers. Is there a reason why this is not a good idea? Any advise you can offer would be greatly appreciated. Thanks. -Larry