Galileo Computer Speed Technical Details
The Galileo Computers are all 8 bit processors, whereas the 486 computers are 32 bit processors. This means that the Galileo processors use data in 8 bit chunks, whereas the 486 uses 4 times that amount (32 bits) per instruction. Also, the 486 processors operate many times faster than the Galileo processors. So the 486 is much more powerful than the Galileo processors.
The advantage that Galileo has is that it has 6 of these processors working together. There are three processors that each have a different set of tasks that they are assigned to do, and the other three processors back them up. This way, if one fails, another one is available to take its place.
These processors talk to each other via a dedicated simplex serial data bus, that is shared by the processors and all of the spacecraft subsystems. This data bus is also redundant, so the loss of one component does not kill the data system.
Speed:
The 486 uses pipelining and other tricks to approach one instruction per clock cycle, while the 1802 processors are old technology and can perform only one instruction every 4 clock cycles. So that means the 486 is an additional 4 times faster, or a cumulative 164 times faster than the 1802 processors.
An additional consideration is that the 486 implements high level commands in microcode, and has a much richer instruction set. High level actions such as division are available from the 486, whereas the 1802 does not do division, which requires additional code to implement.