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PCB Design and Specifications

The cards from Gigabyte both use a unified PCB design that is different from the reference Radeon HD 3870 and HD 3850. The azure color of the PCB is one difference that strikes the eye immediately. ATI Radeon cards are usually red. Both cards being identical, we’ll describe the senior model GV-RX387512H.

Like ATI’s reference samples, the Gigabyte cards use a two-phase GPU power circuit with four power transistors in each channel. As we’ve already noted, Gigabyte installed low-RDS(on) transistors on these cards for lower heat dissipation of the power circuit. Coupled with the ferrite-core inductors, this also increases the efficiency of the circuit. As for solid-state capacitors that feature a longer service life, they are not something extraordinary. You can often find them on top-end enthusiasts-targeted mainboards.


A Nexsem NX2420 is the controller of the GPU power circuit. It is a compact counterpart of the NX2416 PWM-controller we have seen before. A single-phase voltage regulator with a Nexsem NX2124A controller is responsible for the memory chips. This simple circuit is quite okay because the power consumption of the 55nm RV670 core is rather low. However, both cards from Gigabyte have an additional 6-pin PCI Express 1.0 connector with a load capacity of 75W. There is a seat for a standard 4-pin fan connector in the bottom right corner but the connector itself is missing because the cards are equipped with Zalman’s coolers. Instead, there is a 2-pin header located at the opposite edge of the PCB, near the bottom DVI port.

The two cards are identical on the left. Their wiring is the same as the left part of the PCB of the reference Radeon DH 3850 because both of them use GDDR3 memory. Each card has 8 chips of memory. The GV-RX387512H is equipped with Samsung’s K4J52324QE-BJ1A chips with a capacity of 512Mbit (16Mbit x 32) and capable of working at 1000 (2000) MHz. This is indeed the frequency they are clocked at on this card. For comparison, the original Radeon HD 3870 carries Samsung’s K4U52324QE-BC08 chips of GDDR4 memory clocked at 1125 (2250) MHz.

The junior model, GV-RX385256H, uses memory from Hynix. The HY5RS573225BFP-14 chips have a capacity of 256Mbit (8Mbit x 32), a voltage of 1.8V and a rated frequency of 700 (1400) MHz. The chips are clocked at their rated frequency on this card.

We don’t quite comprehend why Gigabyte equipped the GV-RX385256H with such slow memory while the reference Radeon HD 3850 has a memory frequency of 830 (1660) MHz. We doubt the Hynix chips will be any good at overclocking, which means the GV-RX385256H is going to be inferior to the Radeon HD 3850 in games. The GPU may save the day to some extent if overclocked well enough.

Both cards carry RV670 chips with hard-to-understand markings typical of ATI’s GPUs.

The only useful information you can learn is the manufacturing date. Here, it is the third week of the current year (January 13-19). The GPU has its full configuration on each card: 64 superscalar execution modules with 5 ALUs in each (a total of 320 ALUs), 4 texture processors roughly equivalent to 16 conventional TMUs, and 4 raster back-ends equivalent to 16 ROPs.

The execution modules support DirectX 10.1 extensions. Nvidia’s GPUs don’t offer this support as yet. The superscalar architecture of the RV670’s execution modules is known to be its bottleneck because it requires meticulous software optimizations for all of the ALUs in the 64 shader processors to be utilized effectively. This GPU also has low performance when filtering textures because it has only 1 filter unit per 2 address units.

The GPU clock rates coincide with those of the reference cards: 775MHz for the senior model and 670MHz for the junior model. You should be aware that despite the single declared core frequency (without the division into domains as in Nvidia’s GPUs) the RV670 actually has a number of internal frequency zones. This allows to control the power consumption of the core flexibly by means of ATI PowerPlay technology.

Both cards can be used in CrossFire configurations with two, three or four GPUs, so they have two CrossFire connectors each. A CrossFire subsystem is not necessarily symmetric. The cards can work together with a Radeon HD 3870 X2 but the amount of graphics memory available for 3D applications will equal the smallest amount of onboard memory among the graphics cards in the configuration. In other words, there is little practical sense in joining a GV-RX385256H with a Radeon HD 3870 X2 or GV-RX387512H because the amount of graphics memory will be limited to 256 megabytes which will make a bottleneck for modern games that often require more memory.

Each card from Gigabyte has two dual-link DVI-I ports and a universal 7-pin analog video output that supports RCA, S-Video and YPbPr formats. The RV670 core incorporates an audio controller and supports audio-over-HDMI but the kit doesn’t contain the adapters necessary to use this feature. Besides, the audio core driver doesn’t support Dolby TrueHD and DTS-HD formats – the PC is yet inferior to Blu-ray players in this respect. The connectors are all covered with protective gags.

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