A term coined by John Backus
of FORTRAN fame
. This means that in a Von Neumann
architectured computer has an important bottleneck
: the memory
. All of the data, the names (locations) of the data, the operations to be performed on the data, must travel between memory and CPU a word at a time.
This means, like for any bottleneck, the speed of a computer system is determined by the speed of the slowest component. There's no use in having a blinking Pentium XII
@ 50 GHz
when the clock frequency of the RAM only is 133 MHz
. What really makes it faster (a little) is not the speed of the fastest component, it's the size and the clock speed of the cache
memory built in the CPU
. If and only if the software loaded needs less than the available cache, the computer will act at true 50 GHz. This is NEVER the case in the current bloat
ed software world. Therefore, we fall back to a world between slow bottleneck and fast bottleneck. And your blinking new PXII 50GHZ is in fact some 10 GHz shit.
The von Neumann Architecture of Computer Systems
by H. Norton Riley