Yet another strange phenomenon on my 286 PC.
After expanding the system with a Lo-Tech EMS memory board and loading the appropriate driver in MS-DOS 5.0, everything initially seemed to work fine. EMS was successfully detected and recognized by games.
However, when I tried to play a round of Spear of Destiny, I noticed graphical glitches. Odd colorful lines stretching across the screen. After a few seconds, the entire game and PC froze, requiring a hard reboot. In further tests, the game sometimes crashed right at the title screen.
The issue only disappeared once I removed the EMS memory. After what felt like an eternity, I came across a post on the VOGONS forum explaining that the problem is related to disk I/O. Simply put, memory access is too fast for the HDD. In this case, there’s a straightforward fix: using a disk cache program like Microsoft’s SmartDrive or HyperDisk resolves the issue. You just need to add the line C:\DOS\SMARTDRV.EXE /X to your AUTOEXEC.BAT.
Note: SmartDrive was only bundled starting with MS-DOS 6.0, but it also works under older versions of MS-DOS if you copy over the SMARTDRV.EXE file manually. I uploaded the MS-DOS 6.22 version of SMARTDRV.EXE for convenience: Download
If you are using a PicoMEM ISA card for EMS emulation, also note that the developer announced a fix for this problem with the next firmware version.
Other games that may be affected by this issue:
Bio Menace
Wing Commander
Commander Keen 4