# Anatomy of a Fullnode

<img alt="Fullnode block diagrams" src="img/fullnode.svg" class="center"/>

## Pipelining

The fullnodes make extensive use of an optimization common in CPU design,
called *pipelining*.  Pipelining is the right tool for the job when there's a
stream of input data that needs to be processed by a sequence of steps, and
there's different hardware responsible for each. The quintessential example is
using a washer and dryer to wash/dry/fold several loads of laundry. Washing
must occur before drying and drying before folding, but each of the three
operations is performed by a separate unit. To maximize efficiency, one creates
a pipeline of *stages*. We'll call the washer one stage, the dryer another, and
the folding process a third. To run the pipeline, one adds a second load of
laundry to the washer just after the first load is added to the dryer.
Likewise, the third load is added to the washer after the second is in the
dryer and the first is being folded. In this way, one can make progress on
three loads of laundry simultaneously. Given infinite loads, the pipeline will
consistently complete a load at the rate of the slowest stage in the pipeline.

## Pipelining in the Fullnode

The fullnode contains two pipelined processes, one used in leader mode called
the TPU and one used in validator mode called the TVU. In both cases, the
hardware being pipelined is the same, the network input, the GPU cards, the CPU
cores, writes to disk, and the network output.  What it does with that hardware
is different.  The TPU exists to create ledger entries whereas the TVU exists
to validate them.
