Method and system for allocating memory space using mapping controller, page table and frame numbers

A method of allocating memory space in a main memory of a computer system including a plurality of devices operable to access said main memory, one of said devices comprising a video controller device for controlling operation of a display, said method comprising:

• during an operating system initialization process, determining a required range of linear addresses required for the video controller to operate said display according to display resolution parameters of said display;
• allocating multiple same-size page frames of the main memory according to the required range of linear addresses for the video device such that said linear addresses correspond to respective ones of multiple, non-contiguous page frames of said main memory, said multiple, non-contiguous page frames providing a video memory display frame buffer accessible by said video controller;
• and
• opening concurrently one of said multiple non-contiguous page frames of main memory by said video controller and another page frame of main memory other than said non-contiguous multiple page frames by another one of said devices.

A method of allocating and accessing memory space in a main memory in a computer system, for controlling operation of a display by a video device, the method comprising:

• programmably allocating first and second ranges of linear addresses required for the video device to operate said display according to selected display resolution characteristics, to physical addresses of individual non-adjacent page frames in the main memory;
• allocating respective first and second sets of multiple page frames of the main memory according to the first and second ranges of video device linear addresses such that said linear addresses in said first range correspond to respective ones of multiple, non-contiguous page frames of said main memory to provide a first frame buffer for said display, and said linear addresses in said second range correspond to different respective ones of multiple, non-contiguous page frames of said main memory to provide a second frame buffer for said display, said first and second frame buffers reserved for video memory;
• storing page frame numbers in map registers in said video device, wherein the page frame numbers correspond to individual ones of said non-contiguous page frames in the main memory;
• operating the video device to generate linear addresses to select map registers containing page frame numbers of said non-contiguous page frames Such that said video device loads said respective frame buffers in an alternating sequence.

A computer system, comprising:

• a main memory having a physical address space;
• a plurality of devices operable to access said main memory;
• at least one of said devices comprising a video device allocated an individual range of linear addresses;
• said video device including a controller operable under operating system control to map the linear addresses allocated to said video device to respective, non-contiguous page frames in the physical address space, said non-contiguous page frames defining video memory space accessible by said video device;
• said video device also including a page table accessible by the controller, the page table containing page frame numbers corresponding to page frames in the main memory physical address space and video device linear addresses in said range of linear addresses mapped to said page fame numbers, said non-contiguous page frames allocated to said video device until said allocation is changed under operating system control;
• and
• said at least one device including a read-ahead controller operable to open a next one of said non-contiguous pages of main memory while a current one of said non-contiguous pages is being accessed.

A computer system, comprising

• a memory having a physical address space;
• a plurality of devices operable to access said main memory;
• wherein at least one device is a video device operable to access frame buffer regions of main memory, said video device allocated under operating system control to multiple linear address ranges, the linear addresses in each linear address range mapped to respective, contiguous page frames in the physical address space, such that the non-contiguous page frames mapped to the linear address ranges define respective ones of said frame buffer regions in the main memory;
• said non-contiguous page frames remaining allocated to said video device until said allocation is changed under operating system control video device further comprising:
• multiple page tables accessible by a controller, each page table containing page frame numbers representing the non-contiguous page frames in the main memory and video device linear addresses in the range of linear addresses mapped to those non-contiguous page frames, and
• said controller selectively operable to generate video device linear addresses in any of said multiple linear address ranges to access the corresponding page table and thereby access the non-contiguous page frame to which a generated video device linear address is mapped.

A computer system, comprising:

• a shared main memory having a physical address space;
• a plurality of devices operable to access said main memory, one of said devices comprising a video device operable to control a display, said video device allocated during initialization of an operating system video device driver, a range of linear addresses determined by display resolution parameters data stored by said video device;
• said video device including a display controller operable to generate linear addresses in the linear address range of the video device;
• said video device including a page table accessible by the display controller, the page table containing programmed entries mapping linear addresses in the linear address range of the video device to page frame numbers corresponding to individual page frames in the shared main memory such that said individual page frames are non-contiguous with one another and provide video memory accessible by the video device;
• said display controller operable to access any of said non-coiitiguous page frames by using the generated linear address associated with that page frame to select the corresponding page table entry;
• wherein
• said video device is operable to access one of said non-contiguous page frames comprising said video memory concurrently with operation of another device to access a page frame other than one of said non-contiguous page frames.

A computer system, comprising:

• a shared main memory having a physical address space, said shared memory comprising
• a plurality of memory channels each accessible over an individual memory channel bus;
• a plurality of devices operable to access said main memory over a channel memory bus;
• one of said devices comprising a video device allocated during operating system initialization of a video driver, a linear address range and allocating a page frame in the physical address space to each linear address in said linear address range, said allocated page frames comprising non-contiguous page frames distributed over the physical address space to define in the shared memory a video frame buffer accessible by said video device until a change in the allocation of said non-contiguous page frames by said operating system;
• a page table correlating addresses in said linear address range to page frame numbers corresponding to said non-contiguous page frames in the shared main memory allocated to the video device;
• a display controller operable to generate linear addresses in said linear address range of the video device to access said page table to select corresponding ones of said non-contiguous page frames for access by the video device;
• wherein
• said video device is operable to access one of said non-contiguous page frames concurrently with operation of another device to access a page frame other than one of said non-contiguous page frames.