root@hal.UUCP (unix superuser) (10/01/84)
I have two *extremely annoying* problems with line printer configurations. Can anybody help? The first system is a VAX-11/750 running 4.2 BSD. The printer is a Dataproducts B300-2 band printer with a Winchester interface. It is connected to a DEC LP11 controller (module M7258) via a 70-11212-25 cable. We get consistent I/O errors. The LP11 sits at 177514 and has the standard vector address of 200. I am able to read/write location 177514 arbitrarily using the VAX console. The kernel recognizes the lp on booting and gets the address and vector right. The entire guts of the printer (it's brand-new) have been replaced to no avail. Cables have been swapped, reversed, inverted, and turned inside-out to no avail. Two different controllers have been tried. Yes, the special file /dev/lp is there. Major number is 15, minor 0. Owned by root; mode 666. I'm testing the printer by trying to 'cat' a file to /dev/lp. The second system is an Integrated Solutions 68010 board running 4.2 BSD. The printer is an old DEC LP02 drum printer. It is connected to a DEC LPV11 Q-bus controller via a 70-11212-25 cable. Consistent I/O errors. Same address and vector as on the VAX. Can read/write location 177514 arbitrarily through the console. Kernel recognizes the device at boot-time, etc., etc. The printer is old but was working fine with an LP11 controller on the 4.1 BSD VAX that this machine is replacing. Controller and cables have been swapped. Special files in place as on the VAX. Anyone who thinks he or she can shed some light on this problem, *please* call me COLLECT at (216) 368-3971. Blaine T. Garfolo CWRU School of Medicine Dept. of Biometry Cleveland, OH 44106
rpw3@redwood.UUCP (Rob Warnock) (10/03/84)
+--------------- | The first system is a VAX-11/750 running 4.2 BSD. The printer | is a Dataproducts B300-2 band printer with a Winchester interface. | It is connected to a DEC LP11 controller (module M7258) via a | 70-11212-25 cable. We get consistent I/O errors... | The kernel recognizes the lp on booting and gets the address | and vector right. The entire guts of the printer (it's brand-new) | have been replaced to no avail. Cables have been swapped, reversed, | inverted, and turned inside-out to no avail. Two different controllers | have been tried. Yes, the special file /dev/lp is there... +--------------- One possible cause of your problem (posted, in case others need it): Back at DCA several years ago, we had some problems with DEC LP8s like this. The Dataproducts printers have a small resistor termination board, generally mounted somewhere near the Winchester connector (but sometimes up in the main electronics package), which contains the pull-up (or pull-up/down) resistors which terminate the printer cable. The LP11 controller, if it is like the LP8, does NOT have internal pullups on the open-collector outputs or the ready/error/... inputs (some of the inputs are actually pulled DOWN below zero, and take a stiff pullup externally to get them up to logic levels). When a printer comes from DEC it is supposed to (!) have the resistors configured for the DEC controller, but when you buy the printer yourself, you have to take that responsibility. The problems that result if the resistors are not correct can range from none (everything's still o.k.) to flakey (SOME characters in SOME positions are SOMETIMES corrupted) to dead (won't even come on-line). It depends also on the length of the cable and the noise environment around the cable (e.g., how good is the frame/power ground between the CPU and the printer?). Swapping cables and controllers doesn't fix it, of course, but in some of the flakey cases it will "change" the problem, causing no small amount of hair-pulling among the diagnosers. In some borderline cases, swapping a controller will fix it for a while... only to fail later. You will need the maintenance manuals for both the LP11 and the printer to verify/reject/correct this problem (if it exists). p.s.: Q: "How many programmers does it take to change a lightbulb?" A: "Programmers don't change lightbulbs, lightbulbs are hardware!" (p.p.s. Santayana said, "Those who do not learn from history are doomed to repeat it." Netnews is a way of spreading history around, so we don't lose it.) Rob Warnock UUCP: {ihnp4,ucbvax!amd}!fortune!redwood!rpw3 DDD: (415)369-7437 Envoy: rob.warnock/kingfisher USPS: Suite 203, 4012 Farm Hill Blvd, Redwood City, CA 94061