It depends.
If you have one IDE hard drive, it will neither increase or decrease performance to have an application on a different partition.
If you have two IDE hard disks on the same IDE cable - one master, one slave - and the partitions are on the seperate disks, you will hurt performance.
If you have two IDE hard disks on seperate IDE cables, and the partitions are on seperate disks, you will probably increase performance.
If you have one hard disk using a SCSI controller, it will neither increase or decrease performance to have an application on a different partition.
If you have two hard disks using SCSI controllers - either on the same cable or different cables - and the partitions are on seperate disks, it will increase performance to put the apps.