Ultra DMA ATA/66In 1997-98 Intel and Quantum created the new Ultra DMA standard called ATA/66. This gives a theoretical bandwidth of 66 MB/sec.
The new system requires a new cable with 80 conductors. The 40 new conductors are used for grounding. In the old version, only 7 cables were used for grounding. The new and very effective grounding removes the so-called crosstalk (i.e. noise remaining in the cable after a transmission).
In ATA/66 the controller had to wait for noise in the cable to disappear before the next transmission. With the new cables the noise is dramatically reduced, the transmissions can follow one by one without delay, and the bandwidth goes up.
The ATA/66 protocol is fully compatible with ATA/33. You may use both type of drives on motherboards either with ATA/33 or ATA/66. Of course you only get ATA/33 performance using a ATA/66 drive on a ATA/33 motherboard. You may upgrade your motherboard with an PCI-based ATA/66 adapter. This is quite cheap.
The new cables also use the same old 40-pin plugs:
If you use a ATA/66 system with a 40-pin cable, the protocol will automatic switch to ATA/33.
According to Western Digital (who had some of the fastest UDMA/66 drives), to use the ATA/66 technology a PC system must have:
See this white paper from WD
ATA/66 was very neccessary for further development of the EIDE harddisks. With the increasing data density the media data transfer rates are going up and up. Therefore the host data transfer rates also must increase. All the time the controlling logic must have a better transfer rate than the media or else performance is reduced. The new EIDE disks coming out from IBM and other vendors delivered such a powerful data output that the old UDMA ATA/33 standard could not cope with it.
Intel supports it with the 810 (Whitney), 820 (Camino) and 840 (Carmel) chip sets.
Other setups include special logic chips to includefull UDMA/66 performance tofor instance a BX-based motherboard.
The ATA interface started in 1996 with ATA/33, which in 1998 was upgraded to ATA/66. Two years later the ATA/100 was released.
As a result, the ATA/100 is reported being more simple to implement in the chipset logic. It is cheaper to produce and fully compatible with both ATA/33 and ATA/66.
There is an upper limit of disksizes at 137 GB in the ATA/100 interface. However there has been made some workarounds to this problem in some comtrollers.
Another technology we will see more and more is ATA-based RAID. Using two or four cheap ATA-disks you can have a very powerfull disk system with doubled bandwidth. This requires a RAID-controller like the Promise FastTrak or a motherboard with onboard controller. Theserequires higher bandwiths in the ATA protocols to show real powerful performances.
The new Serial ATA interface, can pump out 160 MB per second in the first version (Serial ATA 1x or SA1X). Later version promises bandwiths up to 528 MB per second. This will give us headroom for the next five years of harddisk technology improvements.
Even more promising is the new cable design of Serial ATA. Instead of 40/80 conducters the cables only holds four conductors. This thinner cabling is great news for everyone putting together his own PC. I also expect the number of onboard ATA-channels to increase from 4 to 8.
Serial ATA probably will kill the remaining hope for generel use of the IEEE 1394/FireWire interface for PC's harddisks. This was never really supported by Intel.
Hopefully the new interface will operate with a command queue, which has been a great lack in ATA-design compared to SCSI.
To learn more
Read more the boot process and system bus in Module 2b
Read about file systems in module 6a
Read about I/O buses in module 2c
Read about the motherboard chip set in module 2d
Read about RAM in module 2e
Read Module 5c about SCSI, USB etc.
Copyright (c) 1996-2005 by Michael B. Karbo. www.karbosguide.com.