# 16.3.4 Virtual machine MMU

The MMU of the virtual machine is linked with the internal radare IO. This means that you can use for example map multiple files in a virtual space with 'o file <virtual-address>' to create a static environment of a debugger one.

If you are using the radare virtual machine to evaluate code and determine register values and so on you will not be interested into real memory writes because this will make the memory of the debugged program be modified without executing real code and then probably segfault.

To solve this problem. The radare virtual machine implements a cache system that records all the write operations and map them into the read operations. This option can be enabled and disabled with tme 'vm.realio' eval variable:

    [0x4A13B8C0]> e vm.realio = true    ; disable cache write protection