Do you have APC installed on your server?
If so, then you can use this to cache the core. This is faster than hitting the filesystem anyway.
You WILL need those lines configuring the cake_core, just be sure to set
$engine = 'Apc';
above the cache configuration lines.
If using APC on a shared server, it's important to set your prefix properly, I use the following config which works on shared hosting with multiple cake apps installed:
Cache::config(
'_cake_core_',
array(
'engine' => $engine,
'prefix' => $prefix . 'cake_core_' . Inflector::slug(ROOT),
'path' => CACHE . 'persistent' . DS,
'serialize' => ($engine === 'File'),
'duration' => $duration
)
);
Alternatively:
You don't need root access to set permissions for that folder, all you need is FTP access. You can set the permissions for app/tmp/* to 777 using FTP, which is what I do for some other temporary folders that I use.