SQL Server Express 2005 Memory Limit per instance?

[localzuk]

Is the 1GB buffer pool limit imposed by SQL Server Express 2005 on a 'server wide' basis (ie. the limit applies to all instances, so they all share a 1GB buffer pool) or is it per instance (so each instance gets a 1GB buffer pool)?

I've yet to find a site with clear advice on this particular issue.

[SYNACK]

I had always assumed that it was per instance, did some checking and that does appear to be the case. This is why my web filtering and app servers run multiple instances.

MS-SQL Express 2005/2008 multi instance CPU and memory utilization - Stack Overflow

Securing Your SQL Server 2005 Express Edition Server

Installing an independent instance

During setup, if you set the instance name to your own value, the installation program creates an entirely independent version of SQL Server Express. This instance has its own Master database, its own files, DLLs, and memory footprint and its own SA password. Each independent instance starts a separate SQL Server service (program) that consumes CPU cycles, in addition to any other instances that might be installed. While this approach gives you more security in the sense that only those granted access to this instance can see the databases it manages, it's more expensive to implement and maintain. That's because each instance duplicates DLLs, caches, and other in-memory structures.