Intel Corporation

Manish Muthal

Narendra S Khandekar

Vincent E VonBokern

Ashish S Gadagkar

Robert F Kubick

Kuljit Singh Bains

Nilesh V Shah

A method of transmitting a signal from a first clock domain to a second clock domain commences with the generation of first and second clock signals. The first and second clock signals are substantially synchronous and have respective frequencies that are non-integer multiples. A first signal, which is generated in the first clock domain responsive to a transition of the first clock signal that is substantially coincident with a transition of the second clock signal, is prevented from being latched in the second clock domain responsive to the transition of the second clock signal. The first clock signal is prevented from being latched for a time period which is greater than a maximum clock skew which may exist between the first and second clock signals.

Method and apparatus for propagating a signal between synchronous clock

A method of transmitting a signal from a relatively fast clock domain to a relatively slow clock domain is described. The fast and slow clock domains operate according to respective fast and slow clock signals that are substantially synchronized and that have respective frequencies that are non-integer multiples. A first state of an input signal is latched at the commencement of a first period of the fast clock signal, the commencement of the first period of the fast clock signal being substantially coincident with the commencement of a first period of the slow clock signal. In response to the latching of the first state of the input signal, a first output signal is generated and held over the first period, and at least one further period, of the fast clock signal. The first output signal is then latched in the second time domain in response to the commencement of a second period of the slow clock signal, the second period being immediately subsequent to the first period of the slow clock signal.

A computer system, including a graphics controller and a memory controller, employs a Shared Frame Buffer Architecture, and accordingly has a shared memory in the form a bank of DRAMs. The shared memory is accessible by both the memory and graphics controllers. The memory includes a shared DRAM row in which a Shared Frame Buffer (SFB) aperture is defined. An interface selectively provides access to the shared DRAM row by the graphics or memory controller, while providing permanent access to the remaining DRAM rows by the memory controller. This facilitates concurrent access by the graphics controller and the memory controller to the shared DRAM row and to the remaining DRAM rows respectively, in a first memory access scenario. The accessibility of the shared DRAM row by the memory controller, in a second memory access scenario, is also maintained. The interface includes a selector circuit, such as a multiplexor or Q-switch, coupled to receive memory address signals and control signals from the graphics controller and the memory controller via a dedicated bus from each of these controllers. The selector circuit is operable selectively to present either memory address to the shared DRAM row, in which the SFB aperture is defined, and also selectively to provide access to the shared DRAM row by either controller. The selector circuit is operable by a logic circuit, incorporated within the systems controller, which determines whether a memory access request received from the memory controller is to an address in the shared DRAM row, or in the remaining DRAM rows.

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Folsom, CA, United States of America

Manish Muthal