VisionTek Radeon HD 4870 X2 2GB Video Card

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Max Slowik
Kurtis
VisionTek
Aug. 12, 2008

Specifications

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Introduction

When the HD 3870 X2 came out, it was plainly exceptional. It was the first card faster than the ridiculous, and old, 8800 Ultra, and it was an ATI card on top of it. But the really cool thing about it was that it was plain. It worked right--and nobody expected that. Because it used a kind of black box CrossFire, and the only previous dual-GPU video card was terrible, people expected the new tech to showcase old flaws. But it didn't, and how cool was that?

So it's up to ATI to beat its own high score, here. There's a trick to it: the 4870 X2 isn't just a 3870 X2 with better GPUs, the underlying architecture is quite different. Where the 3870 X2 used a PCI-Express bridge chip (basically, a little bit of motherboard sandwiched between the processors), the 4870 X2 is designed so that the two cards share the video memory. ATI calls it a "sideport." And it does more than just simplify the board; it cranks up the bandwidth. Where the GPUs of the 3870 X2 had about 6.8GB/ second of bandwidth between them, the 4870 X2's have a pretty unheard of 21.8GB/ second.

But maybe it's overkill. And there are some more hurdles: a 3870 was pretty lean, power-wise, compared to the 4870, so there's a lot more video card crammed into what is essentially an identical package. Fundamentally, the system still runs on a CrossFire backbone; sideport or not, CrossFire requires a lot of game-specific optimizations that will make or break this card. And let's not forget the X2 boogeyman: how 'bout that microstuttering?

Incidentally, the card is a VisionTek-branded affair, stock and all. The cards I have are OEM, without accessories--the price to pay for getting them early.

First Looks

Once you go black, baby. It's good to see that ATI is willing to use the fastest color in the PCB spectrum. (Black is up to 14% faster than identical hardware using green PCB, you see.) Really, ATI didn't have much choice in the palette-swap, since color is the only thing visually differentiating the 4870 X2 from the 3870 X2.

There are two CF tabs at the top for CrossFire and CFX, and the 6-pin and 8-pin power connectors point up from the face of the card--considerate, given the card's length. Had the power connectors pointed out from the front, the card might not quite fit in some cases (it's 10.5" long).

Like I said, there's no bundle, so let's talk about installing and setting up the aforementioned 4870 X2. It was, colloquially, a pain in the ass. I'm going to say this up front: it has to be the pre-release drivers. They're tweaked Catalyst 8.5 drivers, so out of date, and they wouldn't enable CrossFire out of the box for me. As you can imagine, this was a problem.

In the end, I was never able to get it working right, exactly. In my initial tests, only one GPU would run, the other just idling away. Finally I discovered that if I used two 4870 X2s and disabled CrossFireX, that a single card would run using both its GPUs. Suffice it to say, I'll be re-benchmarking this hardware once the retail drivers are updated and released. At least you can bask in the excitement of the launch and the early performance numbers, in any case.

NOTE: Unfortunately, we haven't have time to take our own photos yet, as we've been extremely busy with the actual testing of the card. When we do the updated review, our own photos will be included.

Specifications

1.912 billion processors (956 million transistors per GPU on 55nm fabrication process)
PCI Express® 2.0 x16 bus interface
512-bit GDDR3 memory interface (ATI Radeon™ HD 4850 X2)
512-bit GDDR5 memory interface (ATI Radeon™ HD 4870 X2)
Microsoft® DirectX® 10.1 support
- Shader Model 4.1
- 32-bit floating point texture filtering
- Indexed cube map arrays
- Independent blend modes per render target
- Pixel coverage sample masking
- Read/write multi-sample surfaces with shaders
- Gather texture fetching

Unified Superscalar Shader Architecture

1600 stream processing units
- Dynamic load balancing and resource allocation for vertex, geometry, and pixel shaders
- Common instruction set and texture unit access supported for all types of shaders
- Dedicated branch execution units and texture address processors
128-bit floating point precision for all operations
Command processor for reduced CPU overhead
Shader instruction and constant caches
Up to 320 texture fetches per clock cycle
Up to 128 textures per pixel
Fully associative multi-level texture cache design
DXTC and 3Dc+ texture compression
High resolution texture support (up to 8192 x 8192)
Fully associative texture Z/stencil cache designs
Double-sided hierarchical Z/stencil buffer
Early Z test and Fast Z Clear
Lossless Z & stencil compression (up to 128:1)
Lossless color compression (up to 8:1)
8 render targets (MRTs) with anti-aliasing support
Physics processing support

Dynamic Geometry Acceleration

High performance vertex cache
Programmable tessellation unit
Accelerated geometry shader path for geometry amplification
Memory read/write cache for superior stream output performance

Anti-Aliasing Features

Multi-sample anti-aliasing (2, 4 or 8 samples per pixel)
Up to 24x Custom Filter Anti-Aliasing (CFAA) for superior quality
Adaptive super-sampling and multi-sampling
Gamma correct
Super AA (ATI CrossFireX™ configurations only)
All anti-aliasing features compatible with HDR rendering

Texture Filtering Features

2x/4x/8x/16x high quality adaptive anisotropic filtering modes (up to 128 taps per pixel)
128-bit floating point HDR texture filtering
sRGB filtering (gamma/degamma)
Percentage Closer Filtering (PCF)
Depth & stencil texture (DST) format support
Shared exponent HDR (RGBE 9:9:9:5) texture format support

Test Setup

In this review, we'll be comparing the VisionTek Radeon HD 4870 X2 to:
- 3870 X2
- 4870
- GTX 280
- 4850
- 9800 GTX

All cards were benched on the same test computer with recent drivers (April or newer), except for the 4870 X2 which used pre-release Catalyst 8.5 drivers.

Intel Core 2 Duo E8400 3GHz

Asus Rampage Formula

2GB Crucial Ballistix Tracer DDR2 800 @ 4-4-4-12 (Sponsored by Crucial)

Thermaltake Toughpower 1000 (Sponsored by Thermaltake)

Windows Vista Ultimate x64 (Sponsored by Microsoft)

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Page 1: Introduction, First Looks, Specifications & Test Setup
Page 2: DirectX 10 Titles
Page 3: DX9, OpenGL, and Synthetics
Page 4: Video, Power, and Overclocking
Page 5: Conclusion

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3 User Comments

1 - Posted by crawlgsx on August 14, 2008 - 3:53 pm

Horrible review. You seem to be the ONLY review on the 4870 X2 that can't get it working right. Your scores don't depict that of the other 1 reviews I've read so far.

2 - Posted by Max Slowik on August 14, 2008 - 6:10 pm

"Hi Max,

I very much enjoyed meeting up in Iceland! Having just finished reading your initial verdict on the 4870 X2, I wanted to send you an email and ask how things are going?

Some of your driver frustrations were shared by me, and I actually ended up postponing the review. Hopefully, I will have it launched tomorrow at pcworld.dk.

Take care,

Kenneth

--
Med venlig hilsen / Kind regards

Kenneth Knudsen
Freelance Journalist / Test Editor, PC World Denmark"

There are a handful of us that have been discussing the possible reasons for not getting the hardware to work correctly. Suffice it to say, we are all running Vista x64 and are using Asus-based X38 motherboards. Bit-Tech also delayed their review for similar reasons.

3 - Posted by johnasmith on August 16, 2008 - 10:02 am

@crawlgsx:
uh did you notice he said it wasn't a FINAL review? i appreciate the honesty, and who knows, once he has all the drivers it might be awesome. but until then this is something i think people need to know. and did i read it right that it did not depict that of the other 1 review you have read? one review? c'mon! i hope that was a mistake on your part and that you have read more than one other review.

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