Original Link: https://www.anandtech.com/show/269



It's always interesting to see how things can be manipulated to appear a certain way at the blink of an eye. A dark and ominous room can be transformed into a tranquil palace by implementing the proper lighting, and the brightest of days can be the darkest of terrors with the proper shade of red in the sky. While psychologists have spent ages attempting to discover how the human mind works, as a manufacturer, the best way to interpret how the market will respond to your product being positioned in a certain light would be to approach your product, not as a manufacturer, but as a consumer; and ask yourself the questions a consumer would be thinking of upon seeing your product. It seems as if there are a few manufacturers out there that aren't the most in touch with how a consumer would approach their product, and luckily, for the sake of competition, those manufacturers don't always boast the greatest in sales. At the same time, because of the fact that there are masters of the way the mind works out there, there are some manufacturers that produce mediocre products and tint their advertising scheme to sometimes fool the consumers that may not have the ability to research their products.

False Advertising?

We see the trend on a day to day basis, with the goal in the market being profit, and customer satisfaction second (how many companies out there would produce a product without making a profit?) it is difficult to judge whether a company is being legitimate in their claims. Case in point would be the Promise Ultra 66 controller card, the back of the box claims performance superior to that of virtually every other hard disk controller standard on the market today, including the much more expensive Ultra SCSI standards. Assuming that the advertising is truthful, how is it that a $70 card with a $200 hard drive could outperform everything else on the market by such a large margin? Could it be that Promise is putting to use some of the classic tricks of the trade? Or could a $70 investment really be the answer to every budget user's dreams? First of all, an introduction to the standard which Promise boasts the first controller card in supporting, let's try and understand the "need" for Ultra ATA/66. For those of you that have already read AnandTech's Ultra ATA/66 Technology Review, you'll want to skip to page 4, otherwise, sit back and enjoy the ride.



Understanding the Need

Here's the problem, you have this data stored on your hard drive and your computer needs to store it in system memory so you can manipulate it. This problem is something that we all face every day, whenever you open a document on your hard drive the disk reads the file, places it in its own buffer (memory) and copies it to your system RAM via your hard disk controller host's bus. The transfer protocol the host's bus uses states the theoretical maximum for performance out of the drive itself, so regardless of how fast your hard drive can read data off of its platter, the transfer protocol is the final decision maker as to what kind of performance you can achieve. Confused?

Let's see if we can simplify things, assume we have a hard drive that can read data off of its platter (data is stored on circular plates known as platters) at a rate of 2MB per second, and let's also assume that the drive has a 1MB buffer. In a single second, the drive is ready to transfer 1MB of data from the buffer to the computer's system memory and provided that the host bus is capable of providing transfer rates of up to 1MB per second, your hard drive will be able to operate at its potential without being restricted in any manner.

Hard drives cannot transfer at their theoretical maximum 100% of the time, in fact, very rarely do they achieve the maximum performance set by their transfer protocols, instead they achieve their theoretical maximum levels of performance in bursts, which is where the term burst transfer rate comes from. This is different from sustained transfer rate which is often much lower than the theoretical maximum of the drive, and is generally the performance you can expect from your hard drive.

Let's take a look at the same hard drive from before, and let's assume that the host bus is capable of providing transfer rates of up to 512KB (1/2MB) per second. While your hard drive may be ready to transfer the 1MB of data it just read from its platter to its buffer after a second, the host bus can only allow for a maximum of half of that data, or 512KB, to be transferred from the buffer to the computer's system memory in a single second. Here's where the problem arises, since the example hard drive only has a 1MB buffer, while waiting for the first 512KB of data to transfer down the bus it can only read another 512KB into its buffer since the bus can only transfer at 512KB per second. It's like having a 100-gallon water tank but only having a pump capable of moving 1 gallon per hour, you have the potential to do much more, but an external force is limiting you.

ata66graph.gif (12712 bytes)
Copyright 1999 Western Digital

This was the case with the old DMA Mode 2 (or PIO Mode 4) transfer protocol standard whose 16.6MB/s burst transfer rate was quickly becoming a bottleneck for newer hard drives. At that point came the need for Ultra ATA/33 that effectively doubled the maximum burst transfer rate to 33.3MB/s. Two years later, it seems as if the advancements in hard disk storage technology have brought us to that limit once again, so break out the calculators, as we're about to double the theoretical maximum once again, Ultra ATA/66 is upon us.



The Specification

Ultra ATA/66 (you'll also hear it referred to as Ultra DMA/66 or Fast ATA-2) allows for a theoretical maximum burst transfer rate of 66.6MB/s, double the maximum of Ultra ATA/33's 33.3MB/s. Another change brought about during the introduction of the Ultra ATA/33 specification was the idea of Cyclical Redundancy Check (CRC) which is something that you've all probably heard of in one form or another at sometime during your computing experience. Basically, before any burst transfers take place both the hard drive and host will calculate what should make it through the transfer and then afterwards the host sends a signal back to the hard drive telling it what actually made it over during the transfer. If the two numbers don't match up then the process is automatically repeated until it is completed successfully. Ultra ATA/66 brings the same CRC feature that Ultra ATA/33 brought to the table, couples it with its 66.6MB/s theoretical burst transfer rate, and adds yet another new feature to the growing list: improved data integrity.

Hard Drive Data Transfer Protocol Comparison

Standard

Theoretical Max. Burst Transfer Rate Cable Requirement Conductors CRC Enabled
PIO Mode 0

3.3 MB/s

40-pin

40 No
PIO Mode 1 5.2 MB/s 40-pin 40 No
PIO Mode 2 8.3 MB/s 40-pin 40 No
DMA Mode 1 (PIO Mode 3) 11.1 MB/s 40-pin 40 No
DMA Mode 2 (PIO Mode 4) 16.6 MB/s 40-pin 40 No
Ultra ATA/33 (Ultra DMA Mode 2) 33.3 MB/s 40-pin 40 Yes
Ultra ATA/66 (Ultra DMA Mode 4) 66.6 MB/s 40-pin 80 Yes

While CRC increased the integrity of transferred data, after approaching burst speeds of 33.3MB/s we begin to truly stress the capabilities of conventional 40-pin IDE cables, and there is a considerable increase in signal "leakage" at the more aggressive timings. The 44.4MB/s mark (Ultra ATA mode 3) is the first marker of unreliability when using conventional cables during burst transfers, what happens is that the data loses its integrity between the hard drive and host controller due to increased timings that the cables were never intended to deal with. At the same time, a standard that required a completely new cable design (such as something similar to what SCSI devices use to achieve their 40MB/s+ burst transfer rates) would never be pursued by the market since that would mean zero backwards compatibility, the solution? Reuse the same cables with a new twist, twice as many conductors.

The Ultra ATA/66 specification calls for the same 40-pin IDE cables that all IDE/EIDE hard drives have used for years now however, in order to take advantage of the specification's higher burst transfer rates the cable specification had to be modified to take into account the more aggressive timing signals that would be transferred over the cables. The result was the same 40-pin IDE cable with twice as many ground lines present in the cable to act as shields between the lines that actually carry live signals back and forth. By doing this we maintain backwards compatibility with all older IDE/EIDE hard drives and ensure data integrity during burst transfers exceeding 33.3MB/s.

cable.gif (4854 bytes)
Copyright 1999 Western Digital

Taking Advantage of Ultra ATA/66

What do you need to take advantage of Ultra ATA/66? There are 4 basic requirements:

  • Ultra ATA/66 support in either your motherboard's chipset or by a third party controller card such as the Promise Ultra 66. Currently, no Intel chipsets support Ultra ATA/66, which will change at the end of the year with the introduction of the Intel Camino chipset. The only two chipset manufacturers to support Ultra ATA/66 are SiS, and VIA. SiS 5600 Slot-1 solution already supports Ultra ATA/66. Although very few motherboards on the market today take advantage of VIA's support for Ultra ATA/66, the VIA Apollo Pro+ or any VIA chipsets for that matter can take advantage of Ultra ATA/66 as long as they make use of VIA's VT82C686A Super South Bridge Controller, which is a bit more expensive than the VT82C596A Mobile South Bridge Controller that most motherboard manufacturers opt to use.
  • Operating System support for DMA transfers via a DMA device driver. Windows 9x and Windows NT currently support DMA transfers by checking the Enable DMA box under Windows Device Manager (Windows 9x only). BIOS support for Ultra DMA Mode 4 (Ultra ATA/66) is also encouraged, although using software utilities you can enable the settings without BIOS support.
  • A 40-pin 80-conductor cable, with a standard 40-pin 40-conductor cable Ultra ATA/66 transfer modes will be disabled and you'll basically have an Ultra ATA/33 hard drive. Ultra ATA/66 drives are backwards compatible with older host controllers, you can use them on non-Ultra ATA/33 controllers however you won't get Ultra ATA/66 performance out of the drives.
  • Finally, you need an Ultra ATA/66 drive to complete the requirements, currently IBM (www.storage.ibm.com) and Western Digital (www.westerndigital.com) have hard drives that are Ultra ATA/66 compliant.


Promising Ultra Performance

With the need for the standard explained, leave it to Promise to come out with the first controller card to support the standard. The Promise Ultra 66 is a half-length PCI card that acts as your basic secondary IDE controller with support for the Ultra ATA/66 standard. This means that the card can function as both a standard controller card (with backwards compatibility for Ultra ATA/33 and prior devices) and an Ultra ATA/66 card.

ultra66.jpg (23384 bytes)

As mentioned above, one of the stipulations for full Ultra ATA/66 compliance, aside from the controller card, is the 40-pin 80-conductor cable, which Promise wisely included in the Ultra 66's package.

The rest of the Ultra 66's package consists of a general User's Manual, although the documentation is primarily an installation guide, it would've been nice had Promise included a better section on troubleshooting.

The physical installation of the Ultra 66 flew by in a matter of seconds, AnandTech's custom built system based on the ABIT BX6 Revision 2.0 quickly accepted the new hardware upon entry into Windows 98. The Ultra 66 was detected by Windows' Add New Hardware Wizard as a SCSI controller card, and using the supplied drivers disk, the drivers were physically installed and the system rebooted. Since the Ultra 66 card requires an IRQ for proper operation, in the case of AnandTech's setup, IRQ 9, there is room for a number of possible conflicts with the hardware installation. To no surprise, the Ultra 66 conflicted with the test system's Digital 21140 PCI Ethernet Card, however after a removal of the Ethernet Card's drivers and a reinstall of the same drivers things went smoothly.

The Ultra 66 can also be viewed as support for 4 additional IDE devices, and when you combine that with the 4 devices your motherboard already supports, if you find yourself needing to use more than 4 IDE devices, the Ultra 66 expands your capacity to 8 drives. The Ultra 66 offers, as briefly mentioned before, two independent Ultra ATA/66 channels that are backwards compatible with Ultra ATA/33.

Overall the card itself is what you can expect from a controller card, it's not going to be a revolutionary design, and at the same time, it's not going to be a problematic peripheral.



The Test

  • Intel Pentium II 400 on an ABIT BX6 Revision 2.0
  • Digital 21140 PCI Ethernet Adapter
  • Promise Ultra 66 Controller Card
  • Western Digital Caviar AC313000 13GB Ultra ATA/66 Hard Drive
  • Matrox Millennium G200 AGP Graphics Accelerator
  • Microsoft Windows 98

These benchmarks show the limitations a maximum burst transfer rate can impose on a high performing hard disk. With the Western Digital 13GB test drive, however, it seems as if the Ultra ATA/33 specification was all that was necessary for the drive as performance didn't really improve over Ultra ATA/33.

In the future, Western Digital's 7200 RPM drive line and other 7200 RPM Ultra ATA/66 drives may show a noticeable performance gain over standard Ultra ATA/33 solutions. Even then, the greatest performance increase will be in high end applications, and not in your conventional business applications (e.g. MS Word, Lotus Smart Suite, etc) according to the benchmark results below.

Conclusion

Right now, there is no need to go out and buy an Ultra ATA/66 hard disk, and because of this, there was no reason for Promise to rush to release the world's first Ultra ATA/66 controller card.

The Ultra 66 won't give you a huge performance increase over the rest of the world's storage technologies, not with today's Ultra 66 hard drives, however shortly, as more and more manufacturers begin shipping faster and larger Ultra ATA/66 hard disks (especially 7200 RPM drives) the need will rise.

With Intel supposedly waiting until September to include Ultra ATA/66 support in their chipsets, there will definitely be a need for a move to the Ultra ATA/66 between now and September, however at the time of publication, you're better off to wait and jump on the Ultra ATA/66 bandwagon when some real hard drives are released.

Expect the coming months to bring more 25GB drives and faster solutions that even break that 25GB barrier with flying colors. When that happens, then that'll be the time to pursue an Ultra 66 or a similar controller card, unless of course you happen to get lucky and find that your chipset supports Ultra ATA/66.

Until then, you can sit back and quietly chuckle at the wonderfully descriptive performance charts that you'll see on the backs of boxes, promising stellar performance, out of a product that has not yet matured to even close to that point.

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