DOCUMENT:Q225497 17-DEC-2000 [win95x] TITLE :PRB: Windows 95 May Fail to Boot Due to I/O Subsystem Failure PRODUCT :Microsoft Windows 95.x Retail Product PROD/VER:WINDOWS:95 OPER/SYS: KEYWORDS:kbOSWin95 kbOSWin95bug kbOSWin98fix ====================================================================== ------------------------------------------------------------------------------- The information in this article applies to: - Microsoft Windows 95 ------------------------------------------------------------------------------- SYMPTOMS ======== Under some circumstances Windows 95 may fail to boot, and will display the following error message: Error: An I/O subsystem driver failed to load Either a file in the .\iosubsys subdirectory is corrupt or the system is low on memory. CAUSE ===== This problem may occur when all memory below 1MB is allocated prior to initialization of Ios.vxd. Ios.vxd must allocate memory below 1MB for use as real-mode buffers. If Ios.vxd can't allocate this memory, it fails to load, which in turn causes Windows 95 to fail to boot. Memory below 1MB is typically reserved for components that specifically request it. However, it is possible that Windows 95 will allocate all memory between 1MB and 16MB during initialization, forcing system DMA buffers (which must lie below 16MB) below 1MB, and therefore preventing Ios.vxd from being able to allocate memory below 1MB. RESOLUTION ========== This problem can be worked around by adjusting the maximum cache size allocated by Vcache.vxd. Vcache.vxd allocates an initial cache size that is no larger than 9MB. Setting the maximum cache size to less than 9MB also reduces the initial cache size, freeing up memory below 16MB and allowing Windows 95 to boot properly. The maximum cache size is set by adding a "maxfilecache" line to the vcache section of System.ini. The following example shows what an entry in System.ini would look like to set the maximum cache size to 6MB: [vcache] maxfilecache=6144 STATUS ====== This is a known problem in Windows 95. It has been fixed for Windows 98. Additional query words: ====================================================================== Keywords : kbOSWin95 kbOSWin95bug kbOSWin98fix Technology : kbWin95search kbZNotKeyword3 Version : WINDOWS:95 Issue type : kbprb ============================================================================= THE INFORMATION PROVIDED IN THE MICROSOFT KNOWLEDGE BASE IS PROVIDED "AS IS" WITHOUT WARRANTY OF ANY KIND. MICROSOFT DISCLAIMS ALL WARRANTIES, EITHER EXPRESS OR IMPLIED, INCLUDING THE WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. IN NO EVENT SHALL MICROSOFT CORPORATION OR ITS SUPPLIERS BE LIABLE FOR ANY DAMAGES WHATSOEVER INCLUDING DIRECT, INDIRECT, INCIDENTAL, CONSEQUENTIAL, LOSS OF BUSINESS PROFITS OR SPECIAL DAMAGES, EVEN IF MICROSOFT CORPORATION OR ITS SUPPLIERS HAVE BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES. SOME STATES DO NOT ALLOW THE EXCLUSION OR LIMITATION OF LIABILITY FOR CONSEQUENTIAL OR INCIDENTAL DAMAGES SO THE FOREGOING LIMITATION MAY NOT APPLY. Copyright Microsoft Corporation 2000.