CMD640

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CMD 640b PCI IDE controller Cmd640b.jpg
CMD 640b PCI IDE controller

CMD640, the California Micro Devices Technology Inc product 0640, is an IDE interface chip for the PCI and VLB buses. CMD640 had some sort of hardware acceleration: WDMA and Read-Ahead (prefetch) support.

Contents

CMD Technology Inc was acquired by Silicon Image Inc. in 2001.

ChipProtocol
SiI/CMD 640MDMA 1
SiI/CMD 643MDMA 2
SiI/CMD 646 UDMA 2
SiI/CMD 648UDMA 4
SiI/CMD 649UDMA 5
SiI0680UDMA 6

Hardware bug

The original CMD640 has data corruption bugs, some of which remained in CMD646. [1] The data corruption bug is similar to the bug affecting the contemporaneous PC Tech (a subsidiary [2] of Zeos) RZ1000 chipset. Both chipsets were used on a number of motherboards, including those from Intel.

Modern operating systems have a workaround for this bug by prohibiting aggressive acceleration mode and losing about 10% of the performance.[ citation needed ]

References

  1. ↑ "- linux/drivers/ide/pci/cmd640.c Version 1.02 Sep 01, 1996". Archived from the original on February 22, 2020. Retrieved February 22, 2020.
  2. ↑ "RZ1000 FAQ". Archived from the original on 2018-09-19. Retrieved 2019-01-03.


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