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- Newsgroups: comp.sys.3b1
- Path: sparky!uunet!zaphod.mps.ohio-state.edu!n8emr!colnet!res
- From: res@colnet.cmhnet.org (Rob Stampfli)
- Subject: Re: rs232 computer connection
- Message-ID: <1993Jan9.161859.17117@colnet.cmhnet.org>
- Organization: Little to None
- References: <C0JrBA.I3z@news.cso.uiuc.edu>
- Date: Sat, 9 Jan 1993 16:18:59 GMT
- Lines: 45
-
- In article <C0JrBA.I3z@news.cso.uiuc.edu> mrjg8679@uxa.cso.uiuc.edu (Michael R James) writes:
- >I have my 3b1 configured to answer on the serial port
- >with a 486 clone running OS/2 on the other end.
- >Problems:
- >1) I'm not getting 9600 baud over this connection, the line
- >appears to very slow with a lot of lag. But file transfers do work.
- >
- >2) Shutting off my 486 crashes the 3b1, although I can disconnect
- >the serial cable and then shutdown with no effect (on the 3b1).
- >
- >Any ideas what my problems might be? Maybe this isn't new but
- >the FAQ doesn't address these problems.
-
- This is from memory, so it may not be 100 percent accurate. There was a
- design bug found in an early version of the 8530 chip that was used in some
- later versions of the serial and combo cards. The card was redesigned to
- cut costs, and the redesign uncovered the bug. I'm not sure of the revision
- number of the affected cards, but I know the "E" series was clean, so the
- problem was introduced after that, I think around "G" or so. If you have
- a board that has one silver box instead of two crystals on it, it has the
- potential for being affected.
-
- The bug manifests itself by allowing the card, when in use, to "ring",
- causing many high level interrupts of the 68010 in quick succession. This
- has the effect of consuming all the processor's time, effectively locking it
- up from the UNIX-PC's perspective. Of the "affected" batch of cards, only
- some actually exhibit these symptoms. The rest are "on the edge", but work.
- The solution is to replace the 8530 chip with a newer one where the bug has
- been eliminated. The old 8530 is still good for service in devices that
- don't stress it in this particular way, like older serial cards or DOS boxes.
- (But, obviously, don't just swap chips with the older cards, since they
- don't have the corrected 8530s.)
-
- If you see your Unix-PC just lock up (LEDS aren't even blinking), try this:
- Disconnect the RS232 connections, one by one, from the serial cards. It
- might take the machine several seconds to recover from processing the queued
- interrupts, but when you disconnect the right cable, the machine will
- eventually come back to life in most cases. (If it has been locked up for
- an exceeding long time, a stack may be blown and a reboot required.) If,
- on the other hand, the machine starts working again, you have found your
- problem. AT&T used to send you a free good 8530 if you complained that you
- had these symptoms. I doubt the offer is still good.
- --
- Rob Stampfli rob@colnet.cmhnet.org The neat thing about standards:
- 614-864-9377 HAM RADIO: kd8wk@n8jyv.oh There are so many to choose from.
-