CMD640
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 640b PCI IDE controller
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.[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.
Мodern 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
- "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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