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D o c u m e n t a t i o nMore About MaxFiles |
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http://mcosre.sourceforge.net/docs/max_files.html
12/15/2006
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D o c u m e n t a t i o nMore About MaxFiles |
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"Max Files" used to be my radio name when I used to work the morning shift for KASM in Palo Alto...
But seriously, Mac OS up to and including 6.x.x only allows 40, count 'em, 40 files to be concurrently open an any given time. This number can be traced back to the earliest Macs - 128K, flat file system, up to two 400K floppy drives. Clearly, with that setup 40 is a reasonable, even generous, number of file paths to allocate at system boot time.
The amount of memory allocated at boot time is controlled by the value stored in the 124th byte of the first block of any bootable Mac volume. The value written to this byte by the Mac OS whenever a volume is made bootable (a System file and Finder are put in the same folder on the disk, more or less) is 10. The actual number of allocated file paths allocated is always four times the number stored at this byte.
So, to increase the allowable number of concurrently open files the value at 124th byte of the first block of any bootable Mac volume needs to be increased.
40 seems like a reasonable lower limit and 340 is close to the upper limit. This upper limit has been tested and found safe on 2,4,5 and 8 meg Mac II series computers. (Mac II family ->) If, however, you get the diagnostic monitor bells on boot up (4 tones, rising) and/or a Sad Mac the number has been set too high for your particular setup.
From System 7.0 (I've read in the tabloids) the number of open file paths will be dynamically allocated during run time. Of course, I could be wrong.
-- Andrew Kohler