pratt@csn.org (Jonathan Pratt) (06/21/91)
We've noticed what appears to be a pretty serious problem with System 7. The problem is that it is relatively easy to get into a situation where the system heap is filled. Unfortunately, under System 7 the standard file packages have been moved to the system heap, so people lose their work when standard file fails to run, or even worse, crashes. This problem has been observed with reproduceability on Macintosh IIci's with 4-5 megabytes ram. When eight megs. are installed the problem is mcuh harder, if not impossible, to reproduce. The easiest way to make the problem occur is run a large program immediately after booting the Mac. By large I mean one whose partition is greater than available memory, but you're allowed to run with what's there. We haven't exper- imented in detail, but you might need to have a window with a lot of icons open in the Finder. You can tell that memory is a problem then because the Finder issues a notification manager call in an attempt to tell you that it wants to close the window. If you now try to do something with standard file there is a good chance of failure, either because PACK #6 cannot be loaded (System and Multi- Finder heaps full), or because of a bug (possibly in a CDEF) that crashes the machine, usually due to an illegal instruction. I theorize that the latter occurs when an unlocked piece of code calls something that scrambles memory (only under lo-mem conditions though, since TMON's heap scrambler doesn't bring it out under normal circumstances). For the skeptics I'll mention that this has happened on several different systems, some with no non-system extensions. In tracking it down I was able to get Microsoft Word 4 to crash as described, so I know it's not just our app. What I'd like to know is whether others have observed this problem, and what work-arounds there are, aside from the ones we use (upgrading to eight megs. or always leaving a couple hundred spare k free for MultiFinder/system heap expansion). Jonathan -- /* Jonathan Pratt Internet: pratt@boulder.colorado.edu * * UCHSC, Box A034 uucp: ..!ncar!boulder!pratt * * 4200 E. Ninth Ave. * * Denver, CO 80262 Phone: (303) 270-7801 */