GXemul Code2

Unfortunately, OpenBSD/sgi will no longer be released after 6.5.

Another kernel to try.

Include cstdio.

Adding Linux for SGI O2 screenshot, and some working URLs.

Minor test machine documentation updates.

Add comment about NetBSD/cats not being able to install via FTP these days.

Updating NetBSD/cats installation instructions from 8.0 to 8.1.

Enabling a MIPS instruction combination for memset which was previously not used, and making it and and strlen instruction combination work with 64-bit mode too. Also describing why not both lb and lbu need to be handled in the strlen_lb_addiu_bne_nop fallback case. (Not much performance improvement in practice, but still.)

The MIPS ALU instruction variants with hardcoded register offsets was not committed; did not improve performance in real-world tests.

Adding link to NetBSD mailing list about lack of X server in 8.x.