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AMD Radeon HD 3850

Michael Brown — Mon, 14 Jan 2008 18:24:37 -0600

We were so pleased with the price/performance ratio of AMD’s Radeon HD 3870 that we awarded Asus’s implementation of it a 9 Kick Ass verdict in our January 2008 issue. We’re not nearly as impressed with the gaming performance of the architecture’s cheaper cousin, the Radeon HD 3850.

The two GPUs share many features, including the same number of stream processors (320), the same 256-bit memory interface, and AMD’s Unified Video Decoder (for offloading all HD-video decoding from the host CPU). Both parts also provide HDCP support on both DVI links, so Blu-ray and HD DVD movies can be displayed on a 30-inch panel at the screen’s native resolution.

And like the 3870, the cheaper 3850 supports PCI Express 2.0, Direct3D 10.1, and Shader Model 4.0 (none of Nvidia’s GPUs support the latter two features, although it will be a long time before this advantage really means anything). But while the 3870 reference design features 512MB of GDDR4 memory and a dual-slot cooler, the 3850 board we received was outfitted with just 256MB of GDDR3 memory, a single-slot cooler and relatively tame core, and memory clock speeds of 670MHz and 829MHz, respectively.

For gaming, the Radeon HD 3870 was at least competitive with Nvidia’s 8800 GT, but the Radeon HD 3850 is a laggard when it comes to gaming at the native resolution of a 24-inch screen (1920x1200). The frame rates we achieved were roughly half of what we obtained with the 8800 GT. If the 3850 cost half as much as an 8800 GT (average street price: $260), this card would garner a Kick Ass award, but at press time, the average street price for these boards was $190. The extra $70 not only buys a faster GPU, but a frame buffer that’s twice as large.

If gaming isn’t your bag, the Radeon 3850 is a fine GPU for watching high-definition movies. But we prefer videocards that can do it all.

White Paper: PCI Express 2.0

Gord Goble — Thu, 10 Jan 2008 18:42:18 -0600

The Peripheral Component Interconnect Special Interest Group (more commonly known as the PCI-SIG) unveiled the PCI Express 2.0 specification in January 2007. If you’re surprised that it took motherboard and GPU manufacturers nearly a year to introduce products based on this technology, keep in mind that it took 14 years for the industry to get this far.
The PCI concept was unveiled way back in 1993, at a time when the PC was just beginning its evolution from glorified word processor and oversized calculator to the full-fledged entertainment and business hub it is today. The ISA (Industry Standard Architecture) bus used in the original IBM PC-compatible architecture was too slow and primitive to handle the new CPUs, videocards, and peripherals being introduced.

Two other bus architectures, MCA (IBM’s proprietary Micro Channel Architecture) and EISA (the open Extended Industry Standard Architecture championed in large part by Compaq), preceded PCI, but neither technology gained significant traction. The VESA bus (promulgated by the Video Electronics Standards Association as a means of enabling faster video performance) was introduced shortly after MCA and EISA. VESA’s popularity was also brief, but the concept of providing an expansion slot dedicated to bandwidth-hungry devices such as videocards lived on.

Learning to Crawl

Intel spearheaded development of the PCI bus in order to provide a direct connection between add-in cards and system memory and a bridged connection between add-in cards and the CPU via the front-side bus. The bridge was necessary because the PCI bus was clocked at a much lower frequency than the CPU. PCI delivered much more bandwidth than ISA (133MB/s, compared to ISA’s paltry 5MB/s), and it delivered plug-and-play capabilities that eliminated the need for jumpers and DIP switches.

The PCI-SIG consistently improved PCI’s performance, and the bus remains viable today, but its usefulness is limited. Since all PCI devices must share the same bandwidth, the bus hobbled videocard performance. Intel also realized that PCI wasn’t fast enough for graphics, so the company introduced AGP (Accelerated Graphics Port) in 1997. AGP, as its name implies, is not a true bus, but it did provide direct access to system memory and the CPU via the front-side bus. It also offered twice the bandwidth of the PCI bus: 266MB/s. AGP’s bandwidth increased to 2.1GB/s with the 2002 rollout of AGP 8X, but since the architecture was limited to a single slot, early dual-videocard solutions such as 3Dfx’s Voodoo SLI (Scanline Interleave) remained dependent on PCI.

PCI Express hit the market in 2004. This architecture delivers the same type of point-to-point connection that AGP has to offer; unlike AGP, however, PCI Express supports multiple devices through the use of a shared switch. Rather than having each device negotiate for the use of the bus, each PCI Express device is granted direct and exclusive access to the switch. And instead of dividing bandwidth between multiple devices, as the PCI bus does, each PCI Express device is provided its own dedicated pipeline. In this respect, PCI Express behaves much like a tiny network on the motherboard.

Data is transmitted serially in packets through two pairs of transmit-and-receive wires called lanes. A one-lane (x1 or by-one) PCI Express connection can carry one bit per cycle in each direction to deliver bandwidth of 2Gb/s in each direction. Multiple lanes can be grouped together, so an eight-lane (x8 or by-eight) PCI Express slot delivers 2GB/s in each direction, and an x16 slot provides 4GB/s each way.

You might also see PCI Express bandwidth expressed in terms of GT/s (GT stands for gigatransfers). Data traveling over PCI Express has a clock embedded in it: Every eight bits of data are encoded into a 10-bit symbol that is decoded when it reaches the receiver. So the bus needs to transfer 10 bits in order to send 8 bits of encoded data. A single PCI Express 1.1 lane, for instance, is capable of a raw data rate of 2.5GT/s, but its effective data rate is 2.5 x (8/10) or 2Gb/s.

PCI Express 2.0

PCI Express 2.0 doubles the data rate of each lane to 5GT/s, or an effective data rate of 4Gb/s. That means an x16 PCI Express slot will be capable of delivering a staggering 8GB/s in usable bandwidth. Videocards will likely continue to be the biggest beneficiaries of the new standard, and not only from the perspective of data throughput. PCI-SIG is working on a new power spec that feeds these power-hungry beasts more wattage.

Point-to-point communication and a switch are key ingredients in the secret sauce that endows PCI Express with its awesome bandwidth. Each lane can acquire exclusive access to the switch, so none of them must compete for bus bandwidth. In this respect, PCI Express behaves much like a LAN.

Even midrange videocards, such as those based on Nvidia’s new GeForce 8800 GT and AMD’s Radeon HD 3870, need more power than the 75 watts a PCI Express 1.1 slot can deliver. These cards are equipped with additional 6-pin power sockets that draw another 75 watts directly from the power supply; high-end cards have two such sockets to draw a total of 225 watts each. PCI-SIG president Al Yanes tells us that the consortium is working on a new power specification “that will support an increased power need to 225 or 300 watts. This spec is targeted for release in the first quarter of 2008.”

The new spec also offers dynamic link-speed management, so the speed of each lane can be increased or decreased on an as-needed basis. This should reduce power consumption, which would be particularly useful for battery-operated notebook PCs. A new link-bandwidth notification scheme will be able to notify software (such as the operating system or a device driver) of any changes to link speed and width. And new access-control services are available to help manage peer-to-peer transactions over the bus.

PCI Express 2.0 will be backward-compatible with PCI Express 1.1, so products designed for the older spec will continue to work in the new architecture. Obtaining the full benefit of the new technology, of course, will require that both the peripheral and the motherboard support the new standard. The fact that Intel just recently began shipping chipsets (the X38 Express) that support the new spec explains why only the very newest GPUs from AMD and Nvidia support PCI Express 2.0. AMD and Nvidia are lagging behind Intel on the chipset side. AMD announced that its new R790 chipset would support PCI Express 2.0 as we went to press. Nvidia is widely rumored to be adding support for the new spec to its unannounced nForce 7 series chipset.

Will you benefit from an early upgrade to PCI Express 2.0? “Initially, only the performance-centric solutions will move [to the new standard],” says Yanes. “But eventually, all will support it since it has functional enhancements that all new PCI-E solutions will want…. Graphics cards have been the solution demanding the most performance. We expect that to continue.” Other early adopter technologies will include enterprise-class storage products and high-speed networking.
Or you could wait for PCI Express 3.0. That standard is expected to increase the interconnect’s bitrate to 8GT/s per lane. That would enable an x16 slot to deliver bandwidth of 12.8GB/s—but products based on that spec aren’t expected to reach the market until 2010.

ASUS P5E3 Deluxe Wi-Fi-AP@n

Gordon Mah Ung — Fri, 30 Nov 2007 18:18:12 -0600

We’ll be the first to admit that we were unimpressed by DDR3 when we first tested it last year, but there’s finally a glimmer of hope.

What changed our minds? Asus’s spanking-fast P5E3 Deluxe WiFi-AP@n mobo, which uses the enthusiast-oriented X38 chipset. The X38’s main highlights are apparently useful DDR3 support and PCI Express 2.0 support. We say “apparently” in reference to DDR3 because we didn’t have a DDR2 version of the board for a direct comparison, but from our tests, the X38 with DDR3 is a winning combination. Also good to have but not a proven performance boost yet is PCI-E 2.0, which doubles the bandwidth of PCI-E 1.0 from 8GB/s to 16GB/s. But does PCI-E 2.0 matter?

Maybe. The jury is still out, but one GPU vendor told us he has seen solid performance boosts from it. We couldn’t test this claim because we were unable to lock our PCI-E 2.0 card at PCI-E 1.0 data rates. Of course, you’ll also need a PCI-E 2.0 GPU, such as Nvidia’s GeForce 8800 GT or AMD’s Radeon HD 3870, to see any benefits. The P5E3 Deluxe doesn’t include SLI support, but the board can run two graphics cards in CrossFire mode.

This mobo also sports a no-nonsense Asus design: There are no blinged-out gamer LEDs or crazy wind tunnels. But that doesn’t mean cooling is an afterthought. A heat pipe keeps the ICH9R south bridge cool and also wraps around the north bridge and voltage-regulation modules.

Other notable features include 802.11n-compliant Wi-Fi support, and the superior Analog Devices audio parts over Realtek hardware.

To test the board and chipset, we set up the P5E3 and an EVGA 680i SLI board with identical hard drives, quad-core CPUs, GPUs, and drivers. However, the P5E3 packed 2GB of Corsair DDR3 clocked at 1,333MHz while the EVGA board used 2GB of Corsair DDR2 RAM clocked at 1,066MHz. With the 2.66GHz Core 2 Quad overclocked to 3.3GHz and running on a 1,333MHz FSB on both platforms, we expected to see minor differences between the two boards, but the P5E3 easily outran the 680i board. The big wins came in gaming, where Quake 4 ran about 11.4 percent faster on the Asus board. FEAR and Valve’s Particle Test were also faster on the P5E3 by a comfortable 5 percent margin. In encoding tests, the P5E3 was faster by a shocking 13 percent.

Those are impressive numbers, especially in motherboard land, where clock-for-clock performance increases of 2 percent are viewed as a win. It’s also more impressive when you consider that the P35 chipset in DDR3 trim was slower than Nvidia’s 680i chipset. However, you’ll have to weigh the value of that speed boost against DDR3’s premium pricing.
The chipset does not officially support a 1,600MHz front-side bus, but we conducted much of our Core 2 QX9850 Penryn testing with the board’s FSB at 1,600MHz with no additional voltage. Intel, however, hasn’t certified the X38 as capable of officially supporting 1,600MHz FSB speeds. We won’t see 1,600MHz until the X48 ships, probably in January 2008.
The X48 launch will make the X38 one of the shortest-lived enthusiast chipsets in recent memory. Should that trouble you? The “unofficial” FSB doesn’t trouble us, but newer is better, and with the X48 launch imminent, the X38 is something of a head-scratcher.

And that’s really a shame, as the P5E3 Deluxe is a great board. It’s fast and solid and packs just about every feature you would want in an Intel system. Unless you’re hung up on getting SLI support, this is clearly one of the best boards available today for Intel.