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.
CMD Technology Inc was acquired by Silicon Image Inc. in 2001.
|SiI/CMD 640||MDMA 1|
|SiI/CMD 643||MDMA 2|
|SiI/CMD 646||UDMA 2|
|SiI/CMD 648||UDMA 4|
|SiI/CMD 649||UDMA 5|
The original CMD640 has a data corruption bug. The data corruption bug is similar to the bug affecting the contemporaneous PC Tech RZ1000 chipset. Both chipsets were used on a number of motherboards, including those from Intel.
Мodern operating systems have a workaround for this bug by prohibiting aggressive acceleration mode and losing about 10% of the performance.
- 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 the Wayback Machine (archived June 9, 2001)
- EIDE flaw
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