Hi,
Please, find below some of our comments.
Actually, the size of the admin_upgrade.php has been increasing from version to version. In addition, version 3.3 has been updated with administrative messages (about 100 kb of code) that are included in all admin scripts. So far, we have reduced the 'admin_upgrade.php' to 500 kb as we have removed all upgrade actions for releases earlier than 2.5. Also, we are to count all other included files that have a total size of at least 200 kb.
All these changes could cause an increase of the memory usage when using PHP5. However, we want to mention that the problem depends on the configuration. So, not all PHP5 configurations face this problem, as they all function in different ways. In most of configurations the 'admin_upgrade.php' and some other administrative scripts work properly with 8 Mb limit that can only prove that PHP configuration does have sense.
In PHP version 5.2.0 the default memory limit is 16 Mb, all later versions have the default value as 128 Mb. So, in order to solve the problem we recommend to change the memory_limit setting in php.ini to its default value corresponding to your version of PHP as shown in the official documentation at:
http://www.php.net/manual/en/ini.core.php#ini.memory-limit
In conlusion, we would like to pay your attention that an increase of the default value of memory_limit setting in the PHP version 5.2.0 and later may be caused by the PHP core functionality regarding resources usage.
WBR,
ViArt Support Team