This application lets you set the size of your system heap for System 6 software.
What's a heap ?
____________
In the case of the system software, the heap is a chunk of memory where the system software stores information it needs to run. Device drivers, like the one that enables your network card to talk to the system software, are installed in the system heap.
Why should I care ?
_______________
Most of the time you don't have to, unless there isn't enough space in the heap to load all of your device drivers. Then some things won't work. If you're running under System 7, the system software will automatically make the heap bigger to load in all of the drivers it needs. However, under System 6, the heap size is fixed when the start up process begins, and if there isn't enough memory left to load a driver, then the driver doesn't get loaded and cannot be used.
How do I know if the heap isn't big enough ?
__________________________________
If there isn't enough room for the network card driver, you have probably had the following experience:
1) You open the Network control panel
2) You switch to something other than Built-In.
3) You get a dialog box which says something like "Could not switch due to an error. Your connection will be reset to LocalTalk."
This is caused by the system trying to load the driver for that network connection into memory, and finding out that there isn't enough heap space for the driver.
What do I do ?
___________
Use System Heap Tool to make your heap bigger so that there will be room for the driver.
The procedure is as follows:
1) Make sure the startup volume you want to modify is on the desktop.
2) Double click System Heap tool.
3) You will get a dialog box that says "This application will let you adjust the size of your system heap for Macintosh System 6 software." Click OK to continue, Cancel to quit.
4) Another dialog box will appear with the message "Select the volume you wish to modify the heap size of." Click 'This one' to select a volume or 'Next volume' to see what other volumes are available.
5) Once you have selected a startup volume, you are ready to set the heap size. The new dialog box on the screen is labeled "Set the system heap size for Macintosh System 6 software." Type in the new heap size and click 'Set Size' to save the new size. The 'Open' button will let you set the heap size on another volume, and 'Quit' quits the program.
What should I set the heap to ?
_______________________________
As a rule of thumb, don’t ever set the heap size to a value that is greater than half of the total amount of RAM you have in your computer.
It will probably take some experimentation to find the right heap size. We recommend increasing the heap size from the default of 128K in jumps of 50K until you can switch network connections without errors. Then you should decrease the heap size in increments of 10K until you get the error again. The heap size you have at this point is too small, so go back to the last heap size that did not create problems, and set it 10K higher to leave the system a little breathing room.
