Ultra DMA Implementation Guide

Introduction

Ultra DMA is a high-speed data transfer feature that allows DMA commands to transfer data at 33.3 MB/s- double the current burst DMA transfer rate of 16.6 MB/s while using the standard 40-pin IDE interface cable.

Ultra DMA lets host computers send and retrieve data faster, removing the bottlenecks associated with data transfers - especially during sequential operations. Western Digital's WD Caviar hard drives that support Ultra DMA are able to transmit and receive data at higher rates resulting in greater performance.

In addition to speed improvements, Ultra DMA delivers new data integrity capabilities to the EIDE interface. Improved timing margins and the use of Cyclical Redundancy Check (CRC), a data transfer error detection code, help to ensure the integrity of transferred data.

Ultra DMA is also recognized as Ultra ATA and Fast ATA-2 and is endorsed by the industry's leading hard drive manufacturers, including Fujitsu, IBM, Maxtor, Quantum, Seagate, Toshiba, Western Digital, and others.

Elements Required to Use Ultra DMA

Operating System Supported Comments
DOS No Ultra DMA not supported by DOS drivers.
Windows 95 Yes with upgrade Not supported in retail release. Microsoft driver supports PIO only. Ultra DMA fully supported by upgrading to the latest Intel Bus Master DMA driver
Windows 95
OEM SR2 (Rev B)		 Yes with upgrade Microsoft driver supports DMA only. CRC checking not supported with this driver. Ultra DMA fully supported by upgrading to the latest Intel Bus Master DMA driver or Microsoft QFE513.
Windows NT Yes with upgrade Not supported in retail release. Microsoft driver supports PIO only. Ultra DMA supported by upgrading to the latest Intel Bus Master DMA driver.
Windows 98 Yes Standard Microsoft driver fully supports DMA and Ultra DMA.
OS/2 Warp 4.0 Yes with upgrade Ultra DMA supported by upgrading to the latest IBM OS/2 Bus Master DMA driver.

Note: Check the Intel web site for the latest Intel driver, and the IBM web site for the latest IBM driver.

Ultra DMA compatible logic on your system motherboard (partial listing)

Hard Drive / BIOS / Ultra DMA Interface

Ultra DMA Technology
Data Transfer Mode PIO
Mode 1		 PIO
Mode 3 		PIO
Mode 4 		Multi-word DMA
Mode 2 		UDMA
Mode 2
Data Transfer
Rate (max.)		 5.2 MB/s 11.1 MB/s 16.6 MB/s 16.6 MB/s 33.3 MB/s

More Ultra DMA Information

  1. Ultra DMA hard drives are backward compatible with existing EIDE/IDE hard drives, CD-ROM drives and host systems. Examples: 1) an Ultra DMA hard drive can be installed in a system that supports EIDE or IDE; 2) the latest motherboards that support Ultra DMA also support standard EIDE interfaces.
  2. Ultra DMA supported hard drives and standard EIDE/IDE hard drives can be used in the same system.
  3. The 40-pin interface cable used on Ultra DMA hard drives must be less than 18-inches in length.
  4. You must contact your system manufacturer to determine if your BIOS and motherboard support Ultra DMA. Some common system manufacturers are listed below.

Known Issues

All new technologies present opportunities for short-term compatibility misalignments. The following information addresses our current areas of concern.

VIA Chipset

Background
There is a known issue involving a small shipment of Western Digital high-performance WD Caviar Ultra DMA hard drives and the VIA VPX and VP2/97 (also marketed as AMD-640) chipsets.

During the initiation phase of an Ultra DMA read data transfer, a series of commands are issued by the hard drive, the BIOS, and the VIA chipset. A deviation from standard protocol by the VIA VPX and VP2/97 chipsets is causing the system and the hard drive to go out of synchronization, resulting in a system that does not respond or locks up.

Hard Drives Affected
The specific Western Digital hard drives affected have CCC:C1 firmware, were shipped between 9/10/97 and 10/8/97, with model numbers AC35100 and AC36400.

Solution
If using an Ultra DMA hard drive in a system with one of the VIA chipsets specified above, you must disable Ultra DMA. A hard drive firmware workaround solution has been developed to accommodate systems using the VIA chipsets specified above. Current shipments of Western Digital hard drives are not affected by this VIA chipset issue.

Microsoft Driver

Background
The Windows 95 OEMSR2 device driver does not successfully recover from the CRC error and retry operations that can occur in Ultra DMA mode. The computer may hang with a blue screen error while the hard drive is being accessed.

Solution
The Microsoft QFE513 driver release corrects this issue and is now available to OEMs. Contact Microsoft technical support for additional information. The latest Intel Bus Master DMA driver supports Ulta DMA and the CRC error recovery process. If you have an Intel chipset, this solution is available to you. If you have a chipset other than Intel, contact your chipset manufacturer for the correct driver.

Windows 98 supports Ultra DMA and the CRC error recovery process.