This Preferences page contains options that control how zMUD uses memory (RAM). Most of these preferences are local to the specific character.
zMUD actually uses memory very efficiently but also uses a lot of memory in order to provide a large scrollback buffer and to achieve the highest scrolling speed possible. Fast scrolling is the number one design parameter in zMUD and using more memory makes this possible. However, you still have some limited control over the memory usage.
When zMUD creates a new window, it only allocated memory for a small number of lines (usually a screenful). As more text is received, zMUD continues to allocate lines in blocks of a screenful until the Max Lines setting for that window is reached. When the maximum number of lines is reached, old lines are discarded as zMUD scrolls.
You can set the maximum number of lines for the main MUD windows, the child windows created with the #CAPTURE and #WINDOW commands, and for the editor. You normally want the main MUD window and editor settings large to handle a large scrollback. Note that the scrolling speed of zMUD is independent of the number of lines in the scrollback buffer. On 32-bit systems, the number of lines in the scrollback is limited only by your available memory (RAM). zMUD requires about 512 bytes per line.