Yes you would be correct this model only supports upto 3.3GB of RAM. see info below:Date: 29/04/2008 Item number: 233170228 Title
RAM upgrade for AMILO Si1520 Description
After upgrading the RAM for AMILO Si1520 to 4GB, there are only 3.3GB recognized. Solution
The AMILO Si1520 is released with 2x 1GB RAM.
No support with 4GB.