Closer Look at ATI Radeon HD 4850

PCB Design and Specs

Unfortunately, we received the senior model, Radeon HD 4870, a little too late to make it to our today’s article, so today we will only discuss the junior card, Radeon HD 4850. Since all performance-mainstream and high-end graphics boards that are released at the launch day of a product are made under supervision of their developer by contract manufacturers, from now on we will refer Power Color HD 4850 graphics card as ATI Radeon HD 4850 to simplify the read.

ATI Radeon HD 4850 is less interesting from a technical standpoint as it uses common GDDR3 memory. On the other hand, it may be the more appealing product in the buyer’s eyes because it comes at a lower recommended price ($199). We will discuss the technical features of the ATI Radeon HD 4870 and Radeon HD 4870 X2 later, when these graphics cards hit the shops.

Thanks to the meticulous optimizations of the graphics architecture, the developer has managed to come up with a new-generation graphics card that is theoretically comparable to the Nvidia GeForce 9800 GTX but is no larger than the ATI Radeon HD 3850. The ATI Radeon HD 4850 does not look serious. With its modest appearance of a mainstream product, it doesn’t seem to contain an impressive potential.

The new Radeon HD 4850 is compact, its PCB being no longer than the PCB of the Radeon HD 3850. As a matter of fact, there are few external differences between these two cards. The only difference that catches the eye is the fan with numerous blades. Of course, the most exciting things are hidden beneath the cooler and we removed it to have a look at the new card.

The power circuit of the Radeon HD 4850 is astonishingly simple despite the declared power consumption of 110W. Like on the previous card, the GPU voltage regulator is based on the dual-phase PWM controller uP6201 from uPI Semiconductor – we have seen this chip on other products from ATI. The load-bearing section consists of eight Infineon OptiMOS 3 transistors, four in each phase. So, there are no differences from the Radeon HD 3850 here. Notwithstanding the two phases only, you shouldn’t worry about the power circuit. Experiments with extremely overclocked Radeon HD 3870 proved that this circuit can easily cope with loads much higher than 150W. A separate regulator with an uPI UP6101 controller and two power transistors is responsible for the memory. Having familiar components to deal with, enthusiasts are sure to attempt to modify the power circuit with the purpose of overclocking. Perhaps one of our upcoming reviews will be dedicated to extreme overclocking of ATI Radeon HD 4850.

The power circuit is equipped with only one external 6-pin PCI Express 1.0 power connector. Coupled with the PCI Express slot, this is enough to feed the Radeon HD 4850 whereas the ATI Radeon HD 4870 has two external power plugs and features a more advanced multiphase power circuit.

GDDR5 memory is yet behind the scenes because the Radeon HD 4850 comes with common and ordinary GDDR3. Eight 512Mbit chips (16Mbit x 32, Qimonda HYB18H512321BF-10) make up a 512MB local memory bank. This amount is in fact the required minimum for today. Fortunately, ATI’s solutions use their memory efficiently as opposed to Nvidia’s ones, so we shouldn’t expect performance hits in the most demanding games. Curiously, ATI returned to the traditional L-shaped placement of the memory chips in the new card instead of placing them in a semicircle around the GPU.

The memory voltage is 2.0V. The -10 suffix denotes an access time of 1.0 nanoseconds and a rated frequency of 1000 (2000) MHz. The card’s memory frequency is 993 (1986) MHz, providing a memory bandwidth of 64GBps. Not much if compared with Nvidia’s new solutions, but having a wide memory interface is not enough. The key is in using it effectively. This point has already been proved by the ATI Radeon HD 3800 that was no worse than the Radeon DH 2900 notwithstanding the twice narrower memory bus. And the RV770 features higher efficiency of using the memory bandwidth than the RV670. So, the Radeon HD 4850 is unlikely to suffer a lack of memory bandwidth.

The RV770 die looks large. Indeed, the 956-million-transistor core can’t be small. On the other hand, it measures 270 sq. mm which is only 37% larger than the previous-generation RV670 core (190 sq. mm). Moreover, the RV770 is more complex but smaller than Nvidia’s 55nm G92b core. This is the result of the architectural optimizations coupled with 55nm tech process. You can only wonder how smaller the RV770 is if compared with the Nvidia GT200 which not only incorporates 1.4 billion transistors but is also manufactured on 65nm tech process.

As opposed to the RV670, the RV770 has a protective metallic frame that prevents the cooler from misaligning and damaging the GPU die. The core is marked in an incomprehensible way. Most of it is occupied by a Radeon logo. The rest of the marking is a mysterious set of symbols plus the manufacturing date.

The ATI Radeon HD 4800 is not expected to come in cut-down configurations. Every subunit is enabled in the core: 160 superscalar execution modules with five ALUs in each, 10 large texture processors equivalent to 40 TMUs, and four raster back-ends equivalent to 16 classic ROPs. The GPU frequency is 625MHz. Lower than that of the ATI Radeon HD 3850, but the difference is made up by the new card’s having more TMUs and shader processors as well as featuring various architectural improvements.

Besides that, the core incorporates the CrossFireX interface logic (to support multi-processor subsystems including up to four Radeon HD 4800 cards), display controllers (CRT, DVI, HDMI, DisplayPort) and the UVD 2 video-processor. The latter supports the capabilities described by BD profiles 1.1 and 2.0, particularly the decoding of two video streams necessary for such features as Picture-in-Picture. The execution section of the RV770 chip is utilized for laying one picture on top of the other. The functionality of the integrated audio core is enhanced. It can now output eight-channel sound in 24bit/192kHz format and supports Dolby TrueHD and DTS-HD, being compliant with the HDMI 1.3 specification. Nvidia’s solutions can’t match that as yet.

The left part of the PCB is almost empty. The card is equipped with two dual-link DVI-I ports (with support of display resolutions up to 2560x1600), a standard mini-DIN port and a couple of CrossFireX connectors.