While this post is specifically for Tim Shoppa (as the only person that I can think of who can answer), if anyone else has the background, please reply. I believe that I have found a rather inconvenient bug in SDHX.SYS from version Y01.16 (from V05.06 of RT-11) that can cause RT-11 to crash. If I am not mistaken, the same bug is also present in the previous version V01.00 of SDHX.SYS from V05.05 of RT-11. Unfortunately, the bug can cause RT-11 to crash There also seems to be another bug which results in the extended memory status being displayed incorrectly, but otherwise does not cause an actual problem. I realize that RT-11 is rarely used these days and that SDHX.SYS is used even less frequently, but I suggest that these errors really need to be fixed. I would appreciate any suggestions as to how to proceed. Jerome Fine