The Kiwi IC is a very large-scale IC that incorporates the functions of the YANCC IC used in the Macintosh Quadra 700 and 950 computers along with the bus transceivers and several driver ICs. The Kiwi IC provides an interface to the MC68040 on one side and a NuBus interface on the other side. The Kiwi IC is completely compatible with the YANCC IC, so no software changes are necessary to support it.
The Kiwi IC maps certain system bus cycles to NuBus cycles and certain NuBus cycles to system bus cycles. The features of the Kiwi IC include
- support for all types of single data transfers in either direction
- a buffer, one longword deep, for pended writes from the MC68040 to the NuBus
- support for block move transfers between NuBus masters and main memory
- support for pseudoblock transfers between the MC68040 and NuBus slaves
- support for some new functions defined in the NuBus ’90 specification
- the ability to disable pended write operations
Like the YANCC NuBus controller used in the Macintosh Quadra computers, the Kiwi IC generates an interrupt when there is an error involving the write buffer. System software controls this interrupt by means of a control and status register in the Kiwi IC.