You can't create a console program with unlimitless scrolling buffer under Windows without workarounds (fake your console with GUI one or create console program which uses scrolling keys (up, down, left, right) to display your output from TStringList class. In this case you can't use default console window scrollbars. You can't even have access to them under console program due to their Windows nature/security.) .Top buffer line will be always replaced with new one and old ones will be lost when your output lines grow greater than maxium scoll buffer row.
Sorry for resurrecting this old thread, but I've run into the same problem and I think the OP was misunderstood. In current windows10 console, scrollback is broken for freepascal console programs.