5 ms·
I believe in the specific case of L4/Alpha, the PALCode did perform the context switches. Granted, I doubt it was as robust as the VMS or Tru64 PALCode version
by KMag 4y ago
I believe in the specific case of L4/Alpha, the PALCode did perform the context switches. Granted, I doubt it was as robust as the VMS or Tru64 PALCode versions that were production-ready.
- p_l 4y agoPALcode implemented context switches for all systems, including Linux (which uses Digital Unix PALcode). Specifically, PALcode covered various internal details of the CPU presenting unified interface to OS - each CPU needed custom PALcode implementation, though IIRC there were only few mandatory PALcode calls (related to memory barriers, iirc). The kernel covered switching OS-specific structure pointers over, PALcode handled all sorts of MMU, TLB, PASID indexing of TLB, internal CPU state etc. L4/Alpha PALcode was limited to specific set of CPUs it was implemented for, so unlike VMS, NT or Digital Unix PALcode it wasn't available outside of those few machines.