If we define time machine as an apparatus, which can transfer information from a possible future to the past – does a PC, which is sufficiently powerful to run simulations (i.e. has at least 4K memory), meet this definition?
Consider the following.
You want to know what will a potential future be, if you choose a certain course of action. This information will allow you to decide if to follow this course of action or a different course of action.
You develop (or pay someone else to develop) a program which simulates the future to the level of detail which you need. You run the program on your PC and analyze the simulation results. Finally you decide if you want this future or some other future.
However, simulating the future is philosophically equivalent to having a look at the future. Of course, you’ll not see everything in the future. But a time machine would not transfer from the future to the past every detail about the future world. Both PC and time machine will tell you as much as you need to know about the future. Sometimes less than you need, due to fog (time machine) or numerical difficulties due to chaotic regions in the simulation (PC).