vb81

vb81 is a fast Z80 emulation core for Windows systems. It has improved performance for both standard and hi-res displays, and has a 3x magnification option. It also has the option to write to the shadow ROM area, which some games use for hi-resolution graphics and custom character sets.

Main features:
-Significantly faster Z80 emulation core. You should have no problems running vb81 at full speed in both SLOW and FAST modes even on a relatively low-spec Windows system
-Improved performance of both standard and hi-res display routines.
-Fixed a couple of bugs in the keyboard support which caused many games not to respond to key-presses.
-Added new 3x display magnification option.
-New 'Allow writes to shadow ROM area' option allows access to the 8K-16K area of the memory map. Some games use this to provide hi-resolution graphics and custom character sets (FROGGER- for example).
-Fixed a bug in the interrupt routine that caused FRAMES to be incremented wrongly. Some games such as Rocket Man froze after a few seconds or minutes of playing.
-Fixed some minor bugs in the Z80 emulation. I believe the CPU emulation is now 100% correct in terms of timing, flag operation, and support for undocumented opcodes -- let me know if you think otherwise!
-Playtested against literally hundreds of ZX81 games to ensure full compatiblity. The only known problem is ZX-Xtricator, which has a custom overscanned hi-res display routine that does not yet work properly with vb81.
-Emulates both SLOW and FAST modes.
-Emulates psuedo hi-res graphics routines as used by innovative games such as Forty Niner, Rock Crush, Dan's Revenge, and Rocket Man.
-Supports loading and saving of standard ".P" tape files used by various other ZX81 emulators.
-Includes optimised 'standand' and 'double-size' display options.
-Emulates undocumented Z80 op codes, and correctly emulates all bits of the Flags register.
-Native 32-bit Windows application runs under Windows 95, Windows 98, NT, and Win2K.
-Emulates Memotech's MemoCalc spreadsheet ROM.