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.
| Chip | Protocol |
|---|---|
| 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 |
| SiI0680 | UDMA 6 |
Hardware bug
The original CMD640 has data corruption bugs, some of which remained in CMD646. The data corruption bug is similar to the bug affecting the contemporaneous PC Tech (a subsidiary of Zeos) RZ1000 chipset. Both chipsets were used on a number of motherboards, including those from Intel.
ะodern operating systems have a workaround for this bug by prohibiting aggressive acceleration mode and losing about 10% of the performance.
References
- "- linux/drivers/ide/pci/cmd640.c Version 1.02 Sep 01, 1996". Archived from the original on February 22, 2020. Retrieved February 22, 2020.
- "RZ1000 FAQ". Archived from the original on 2018-09-19. Retrieved 2019-01-03.
External links
- 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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