MITAC 8575
Service Manual

8575 N/B Maintenance
Two separate buses, Host-t-GUI in the width of 64 bit, and GUI-t-Memory Controller in the width of 128 bit are devised to ensure concurrency of Host-t-GUI streaming, and GUI-t-MC streaming. In PC133, or DDR266 memory subsystem, the 128 bit GUI-t-MC bus will attain the AGP4X or AGP 8X equivalent texture transfer rate, respectively. The Memory Controller mainly comprises the Memory Arbiter, the M-data/MCommand Queues, and the Memory Interface. The Memory Arbiter arbitrates a plenty of memory access requests from the GUI or AGP controller, Host Controller, and I/O bus masters based on a default optimized priority list with the capability of dynamically prioritizing the I/O bus master requests in a bid to offering privileged service to 1) the isochronous downstream transfer to guarantee the min. latency & timely delivery, or 2) the PCI master upstream transfer to curb the latency within the maximum tolerant period of 10us. Prior to the memory access requests pushed into the M-data queue, any command compliant to the paging mechanism is generated and pushed into the M-CMD queue. The M-data/M-CMD Queues further orders and forwards these queuing requests to the Memory Interface in an effort to utilizing the memory bandwidth to its utmost by scheduling the command requests in the background when the data requests streamlines in the foreground.

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