Simple-As-Possible computer introduces all the cruicial ideas behind computer operation without burying you in unnecessary detail.
The figure shows the architecture of SAP-1, a bus-organized computer. All register outputs to the W bus are three-state; this allows orderly transfer of data. All other register outputs are two-state; these outputs continuously drive the boxes they are connected to.
原文：http://www.cnblogs.com/mengdie/p/4586246.html