In Solaris 7 (Intel Platform Edition), there is a new tunable called kernel base that can be used by system administrators to change the maximum size of kernel or user space.
Intel x86 and compatible processors support only 4GB of virtual address space. By default, in the Solaris operating environment, this is divided into 3.5 GB for user processes and 512 MB for the Solaris kernel. This may not be appropriate for certain workloads. For example, a kernel-based network cache accelerator can benefit from a larger virtual address space for the kernel, while a system with 4GB of physical memory running transaction processing operations using an RDBMS such as Oracle may want to increase space for user processes.
System administrators can change the default allocation through the kernel base property. kernel base defines the beginning of kernel address space; its default value is 0xE0000000. Lowering kernel base below 0xC0000000 makes a system non-ABI compliant and some ABI-compliant user programs may not run.
Use eeprom(1M) to set the tunable kernel base to the desired value (in hexadecimal). The change takes effect when the system is rebooted.