differences_between_us-ii_and_us-iii [HelenOS UltraSPARC port]

run on machines with different firmware
- difference in the boot process (see http://helenos-blog.pavel-rimsky.cz/?p=3)
- claiming physical memory for the boot allocator failes on US-III (workaround: decrease the amount of memory available for the boot allocator from 1024 kB to 256 kB)
- the firmware is setting the value of the WSTATE register to 0×00 on US-II and to 0×05 on US-III

cache sizes
- US-II has a 32kB 2-way associative I-cache, US-III has a 64kB 4-way associative I-cache

cache coherency
- US-III cache is write-invalidate, so there is no need to invalidate its entries after self-modifying the code
- the argument of the FLUSH instruction is ignored on US-III

memory
- US-II supports a 44-bit virtual address space and a 41-bit physical address space; US-III supports a 64-bit virtual address space and a 43-bit physical address space
  - therefore the TTE is slightly different on US-III: the DIAG field has been removed, so the PA size can be 43 bits (other bits gained by removing DIAG are impl. dep./reserved)
- US-II has one 64-entry TLB for D-MMU and one 64-bit entry TLB for I-MMU, whereas US-III has three TLBs for D-MMU (16 + 512 + 512 entries) and two TLBs for I-MMU (16 + 128 entries)
- definitions of various ASI register addresses and values differ

Simics support
- graphics console is fully supported on Sunfire; there are a lot of limitations on Serengeti (https://www.simics.net/mwf/topic_show.pl?tid=18784) which make the graphics console almost unusable