Had this game on the TODO list for a while. When I recently tried to play it again, it was practically unplayable. Turned out it was much buggier than I was aware of. So I put together a patch which solves most of the problems people have been experiencing over the years. It even runs on the ancient Windows NT 4.0 (in software mode at least), which was totally unsupported until now. Of course, it runs great on Windows 10 as well and should theoretically run on computers with varying graphics hardware with nice graphics with the help of Glide wrapper. I recommend nGlide.
So now we assume you've already got it installed and got around the issue of 64-bit OSes not being able to run 16-bit installer. For base game, Gold Patch is prerequisite for applying my patch. For Nitro Pack, the only thing that's needed is A3D-Live! wrapper (included, can be installed any time) to fix the all-sounds-playing-at-100%-volume-at-player-position problem because game's DirectSound code is broken for some reason.
As usual for my patches, the goal is to get the game working with minimal amount of compatibility options. So you can turn off any compatibility options you've previously set on I76.EXE/nitro.exe executable and apply Disable_Interstate76_Compat_Shims.reg registry file. Game should have Modify permissions for its own folder. If it's located under Program Files and settings related to UAC/file system virtualization haven't been changed, there shouldn't be any problems, plus each user will have its own save files. Applies to Windows Vista and beyond. For older systems/other install locations, Users group may have to be granted Modify permissions explicitly on game folder (assuming we're running as user with limited rights).
Download link: Google Drive
Here comes the changelog:
Common:
- Fixed some, worked-around other memory management bugs, which improves stability; mission 12 -> 13 transition works in I76, also no more need for EmulateHeap shim (the only semi-useful thing from Windows 95 compatibility mode), which doesn't actually fix anything.
- Fixed game freezing when clicking menu option if hardware sound acceleration is available.
- Fixed certain startup crashes/errors when initing graphics with 3D accelerated renderers enabled (Glide/D3D).
- Skipped some unnecessary CPU checking code containing privileged instructions (crashes at startup if privileged instruction exceptions aren't ignored by the OS).
- Corrected memory checking code to avoid error about insufficient memory when system has more than 2 GB of RAM.
- Fixed an issue with laggy physics simulation that occurs when the system has been running for several days.
- Fixed an issue with music playback not restarting during gameplay after the track has finished playing (another issue that occurs when the system has been running for extended periods of time).
- After the music track has finished playing during gameplay, the mission specific track will play again now instead of always the 1st music track.
- Rearview mirror refreshes every frame now.
- Includes Shane's netcode patch for compatibility with NAT, Nitro Pack version also forwards port on router when hosting the game (if UPnP is supported).
- Fixed registry handle leaks.
- Added frame rate limiter which defaults to limiting the game to run at 20 FPS to workaround bugs that occur at higher frame-rates.
- GDI windowed mode now works on Windows NT systems.
- Embedded manifest in executables:
- Marked as high-DPI aware.
- Requests version 6.00 of Common Controls Library to enable visual styles in those occassional message boxes.
- Executables have been flagged as compatible with DEP (Data Execution Prevention).
- Clicking Scenarios in main menu will no longer stop music playback.
Some thoughts
At some point, I've read about the magic 24 FPS as the ideal frame-rate to get properly working physics. Obviously, when the game was made, nobody was talking about frame rates as game physics isn't intentionally tied to frame-rate. Devs just write code, overlook some details when implementing it and leave it at that if it appears to work correctly.
Anyway, my issue with the supposedly magic 24 FPS is that 7.62 MM MG firing sound is being interrupted at regular intervals while it sounds fine at 20 FPS, hence why I set the limit to 20 FPS.
Another important thing, the game really only works as long as it does without crashing on Windows 95 by accident. Saw some really bizarre code in there: accessing buffers beyond their boundaries, overwriting variable holding a pointer (handle) to one heap with pointer to another heap, setting some variable based on the content of uninitialized memory.
Some of the memory management bugs are still lurking in there and could cause the crash out-of-the-blue (could be more obvious with player-made maps, with which I'm not familiar with), but the most obvious ones have been identified and fixed. I was going to fix them from A - Z, but the first thing that is found with Page Heap enabled is some access beyond buffer boundary mid-play in some giant function, would need thorough look to identify the start and the end of actually allocated memory.
