"Max Files" used to be my radio name when I used to work the morning shift for KASM in Palo Alto...
But seriously, the current Mac OS (upto 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. The cdev "Max Files" was created to do this chore for those who are too squeamish (sp?) to use the "Edit Boot Blocks" function of Fedit.
To use this cdev just drop it in your System folder and, using the Control Panel, use Max Files to choose a bootable volume and set the number of concurrently open files allowed when that volume is the boot volume. Be sure to click on the "Save New Setting" button to update the volume. The change will take effect the next time the volume is used to boot a Mac.
Notes and Caveats :
This cdev has been designed to limit the number of concurrently open files to values between 40 and 340, inclusive. 40 seems like a reasonable lower limit and 340 is close to the EMPIRICALLY DETERMINED upper limit. This upper limit has been tested and found safe on 2,4,5 and 8 meg MacII 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. Just boot off another disk and use Max Files to lower the number of file paths to be allocated on the troubled disk.
This cdev has not been tested on SEs, Plusses or older machines. If you get a Sad Mac just boot off another disk and use Max Files to lower the number of file paths to be allocated on the troubled disk.
Max Files should be useless if System 7.0 is ever released. From what 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.
This cdev is the property of Siemens Gammasonics, Inc. However it may be freely distributed without charge as long as this notice is included. This cdev may not be distributed for a fee (with the exception of dowloading fees) without the prior written consent of Siemens Gammasonics, Inc. This cdev may not be distributed in any commercial product without the prior written consent of Siemens Gammasonics, Inc.
Max Files was researched, designed and implemented in about 6 hours time. We've been using it for a month in house with no ill effects. The concept and design are straight-forward and simple, and the implementation was straight-forward and compact. HOWEVER, this cdev is experimental and neither Siemens Gammasonics, Inc. nor Andrew Kohler guarentee its suitability or use for any purpose, nor are they liable for any damage or loss of data caused by the use or misuse of this software. This software is provided free of charge "AS IS". The user should take reasonable precautions to preserve data with back-ups when using this software.
Please direct all questions, comments, bug reports, etc. to :
