This figure shows the Extended Computer model that a student builds by extending the Basic Computer model with input interrupt processing. This model introduces two more instructions: Read and Return. Also, the control unit handles input interrupt processing and the RAM contains an interrupt routine that executes when an input interrupt occurs. Again, the functionality not included in this model is greyed out. (Note: this model can be built by using the stand-alone Extended Computer kit or by using the Extended-Computer++ kit or the Computer System kit whereas the latter two are equipped to further implement their respective greyed out functions).

The Extended Computer kit (and only this kit) also includes an ALU chip with sixteen arithmetic and sixteen logic operations. This chip is solely provided to show how to access and use operations of a typical ALU. To maintain simplicity, these operations are not utilized within the CPU logic of the Extended Computer model. However, at this point of the project, a student will be able to compose digital logic that utilizes these operations.

(Construction time: 20 to 23 hours).