New in This Version

• Fix bug that prevented the Configuration GUI from saving to dosbox.conf the last Windows 3.1 theme you applied using the dropdown menu. (joncampbell123).
• Add option to apply vmemdelay to SVGA and linear framebuffer modes (such as VESA BIOS modes), which reduces emulator performance for those modes, but allows you to emulate slower SVGA cards. Due to how some machine types are emulated, this option also enables vmemdelay to affect the PC-98 linear framebuffer, Tandy & PCjr video modes, as well as MDA/Hercules. (joncampbell123).
• Add workaround to CPU reset logic that allows it to work correctly even with dynamic core. Previously, if the guest reset the system, the emulator would crash with an error message about an uncaught C++ exception because C++ exception handling doesn’t work with dynamically generated code. (joncampbell123).
• Correct CPUID family/model/brand values for cputype=pentium_iii. Add CPUID level 2, which returns “processor configuration descriptors”, and return documented Pentium III values. Apparently Windows XP really REALLY cares about these configuration descriptors and will hang in-kernel in an infinite loop at bootup without these apparently really important values. This change makes it possible to boot Windows XP with Pentium III emulation. (joncampbell123).
• Allow values of memsize to represent 4GB or more of RAM. Up to 1TB, if Pentium PSE extensions are enabled, the memalias setting is 40, and “enable pse=pse40” in the conf file. Memalias maximum is now 40, instead of 32. Add code to provide that memory above the 4GB address mark when PSE is in use by the guest OS. Added dosbox.conf option to specify a memory file. When specified, all guest memory is memory-mapped from a file on disk, rather than allocated from host memory or host swap file. To avoid consuming too much RAM on the host, a memory file is REQUIRED to emulate memory at or above 4GB. For best performance with the memory file, make sure the filesystem you place it on supports sparse files, including Linux ext4 and Windows NTFS. (joncampbell123).
• Fix EGA machine type to determine whether CGA RGBI or EGA RrGgBb display is active by vsync polarity, instead of the length of htotal. Several online references state that vsync is negative for 350-line modes, including 350-line to an MDA monitor. This also allows the “enhanced” EGA 320x200 modes in Rambo III to display colors correctly. (joncampbell123).
• Dynamic x86 core: Reflect STI instruction to normal core so that the 1-instruction delay is correctly emulated. This makes it possible to run Windows XP or Server 2003 with dynamic core and SYSENTER/SYSEXIT emulation without random BSODs (joncampbell123).
• Fix default code page. Instead of assuming 437 at all times, use 437 for all IBM PC compatible modes and 932 for PC-98 emulation. (joncampbell123).
• Normal core: Fix STI emulation to enforce the 1-instruction delay by forcing the normal core to execute another instruction right away without providing any opportunity for interrupt processing. This does not break Peret Em Heru, Keen games, and it seems to fix the random BSOD issues with Windows XP and Windows Server 2003 when emulating a Pentium II that supports SYSENTER/SYSEXIT. I’m not clear on why this fix prevents them from crashing, but there you go. (joncampbell123).
• Keyboard emulation: Fix PCjr key delay to match IBM documentation stating how long it takes to transmit one scan code, which is obviously much slower than normal to accomodate the slow CPU and the optical nature of the transmission. This is needed in order for emulation to correctly send Fn+key combinations. At normal key delay, the guest will miss scan codes and function keys will not be reliable. (joncampbell123).
• Keyboard emulation: The 83-keyboard scan codes work differently on the PCjr keyboard because half of them are only accessible by holding the Fn key. The keyboard only sends the base key scan code and the Fn key scan code and the BIOS is expected to convert that to the normal 83-key scan codes expected by DOS software. The problem is some games like “Agent USA” for PCjr are written to directly handle scan codes through IRQ 1 (the fact that PCjr handles keyboard via NMI and reflects to INT 9 is ignored here). Fix this by sending scan codes that emulate holding Fn and pressing the appropriate key. Agent USA expects the user to press F1 by holding Fn and pressing “1”. (joncampbell123).
• Revise VGA doublescan mode, vs bit 7 of the Max scanline register, to correct how VGA doublescans 200-line modes. Revise EGA/VGA text code to divide line by 2 in rendering to match double scanned scanlines, so that the “graphical” text of “After the War” can render properly for machine=vgaonly. (joncampbell123).
• INT 10: If machine=ega, check the EGA switches on INT 10h modeset. Some games force the EGA BIOS to use CGA 200-line text modes by modifying those bits and then setting the mode (“After the War”). (joncampbell123).
• INT 10: Fix “load font” functions to correctly recompute video display end for machine=vgaonly and machine=ega. (joncampbell123).
• INT 10: Like any other 200-line 16-color graphics mode, 200-line VGA text mode needs to program the AC and VGA palette using the CGA RGBI-type palette, not the EGA 64-color type palette. (joncampbell123).
• CPU: Disallow clearing PE bit from LMSW by default, always. You can still allow it through dosbox.conf. It turns out that x86 CPUs never allowed you to clear it that way, even from the Pentium up, even though Intel documentation beyond the 386 never mentions it again. This fixes problems with DOS extenders and VCPI, particularly DOS4GW which for some reason with VCPI likes to try to clear the PE bit when switching to VM86 even though it clearly understands it’s not supposed to be able to clear it. (joncampbell123).
• VCPI: It turns out the VCPI server GDT selectors are expected to be 32-bit, because the protected mode VCPI entry point is expected to be called as if 32-bit far pointer. Correct VCPI entry point to return using RETF, not IRETD, which solves crashing issues with DOS extenders. For the first time, DOS extenders are working with the DOSBox-X built-in implementation of VCPI and most DOS games run fine now with it. (joncampbell123).
• VCPI: Add code to INT 2Fh handler regarding Windows startup/shutdown messages to fill in DS:SI. If EMM386 and VCPI emulation is active and running the DOS machine in virtual 8086 mode, give Windows the proper callback procedure to allow Windows to switch off VCPI vm86 mode on startup and turn it back on during shutdown. (joncampbell123).
• BIOS “POST” screen: Change BIOS logo to PNG format. To avoid having to render a PNG in roughly 10 different video modes, add code to VGA draw code to allow a BIOS logo “overlay” to be rendered independent of the video mode. Depending on machine type load one of four PNG files from disk or from inside DOSBox-X itself. PNG requirements: 224x224 or smaller, bit depth of 8bpp or less, color palette (not grayscale), no alpha channel, and must not be interlaced. For best compatibility, use less than 64 colors, or perhaps just 16 colors. Much like the Windows 95 LOGO.SYS, you can change the logo to your taste by placing specifically named PNG files in the same directory as your dosbox.conf or current working directory. Have fun. Note that this addition requires that you compile DOSBox-X with libpng enabled. (joncampbell123).
• Added dosbox.conf option to specify BIOS logo file. (joncampbell123).
• Added dosbox.conf option to specify a text message, up to 3 lines, at the bottom of the screen during BIOS POST screen. (joncampbell123).
• Fix color glitches in EGA, Tandy, Hercules mode on macOS SDL2 build (output=opengl)(maron2000)
• Add int33 mickey threshold option (Fixes Ultima Underworld) (jpernst)
• Fix configure.ac (disable-screenshot option) (maron2000)
• Fixed codepage switching when loading language file in Traditional Chinese (maron2000)
• Fixed display of some Chinese characters (Traditional Chinese)(maron2000)
• Fixed garbled text and menubar on reset (maron2000)
• Fixed codepage switching when a language file was loaded (maron2000)