The maximum cache size on 32-bit Windows is approximately 1.3GB.  This is the largest contiguous block of memory in the 2GB process address space which can be used for constructing a memory mapped file.  Due to fragmentation of the process space caused by the loading of libraries required by the digital signature verification code, any attempt to specify a cache size greater then 700MB will result in the automatic disabling of the signature check. Significantly larger cache sizes can be used on 64-bit Windows.