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

CMD Technology Inc was acquired bySilicon Image Inc. in 2001.

The original CMD640 hasdata 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] ofZeos)RZ1000 chipset. Both chipsets were used on a number of motherboards, including those fromIntel.

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

• File containing technical information, FAQs, and tests regarding the corruption issues
• Linux's description of how it deals with the CMD640 corruption
• IBM: July 10, 1998 - Warp FixPak TIPS (includes section on how to detect and mitigate CMD640 concerns)
• Intel page detailing the RZ1000 bugs and offering a utility to detect buggy RZ1000 and CMD640 chipsets at theWayback Machine (archived June 9, 2001)
• EIDE flaw

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