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PCB Design, Specifications, Cooling System

ATI developed two different PCB designs for the new entry-level card: a full-size and a low-profile PCB. And we were lucky to get both samples. We will describe the full-size version first as it is the more interesting one due to its design specifics.

Notwithstanding its full-size form-factor, the card is very compact. Most of the PCB is covered with a large needle-shaped heatsink that cools both the GPU and the memory chips.

The power circuit is simple, consisting of two single-phase regulators. The GPU is serviced by the more advanced regulator incorporating two power transistors. The other regulator has only one transistor and is responsible for the memory chips. Both regulators can be reinforced with additional transistors, but it can hardly be necessary as the power consumption of the RV710 is unlikely to exceed even 30 watts. Perhaps this PCB design was developed with ATI’s next-generation entry-level GPUs in mind – they are going to be faster and require more power. Of course, the card lacks an additional power connector. The PCI Express x16 slot can provide the card with all the power it may want.

When we removed the heatsink, we saw that the PCB of this version of Radeon HD 4550 has a cut-out at the back. It must be made to save on textolite. This saving is substantial when it comes to a $45-45 product. There are four Samsung K4W1G1646D-EC12 memory chips at the back part of the PCB, two chips on either side of it. According to the official specifications, these are DDR3 chips with a capacity of 1Gb (64Mb x 16) and a voltage of 1.8V.

The EC12 suffix means a rated frequency of 800 (1600) MHz and this is indeed the frequency the chips are clocked at on this card. The four 1Gb chips provide a total of 512 megabytes of memory. The total width of the memory bus is 64 bits, ensuring a memory bandwidth of 12.8GBps. That’s quite high for such a cheap solution and more than enough for processing HD video content. As for gaming, the Radeon HD 4550 is not positioned as a gaming graphics card, but it may be fast enough at low resolutions, especially in comparison with Nvidia’s opponents. Strangely enough, the memory chips have not thermal pads and are not actually cooled in any way.

The GPU die is small thanks to 55nm tech process and some architectural improvements over the RV730. The marking indicates that this sample of the chip was manufactured on the 30th week of 2008. The rest of the numbers make no sense for an ordinary user. The die packaging lacks a protective frame and does not actually need one. The heatsink is secured properly: its halves are fastened together with nine screws and there is no possibility of misalignment that might damage the chip. A plastic material that looks like chewing gum is used as the thermal interface here. Its efficiency is low but sufficient for a chip that dissipates 20 watts of heats only.

As we already noted, the RV710 boasts advanced specifications for its class. It incorporates 80 ALUs, eight texture processors and four raster back-ends. The GPU clock rate is 600MHz. The peak specified power draw is 20W.

This version of Radeon HD 4550 is equipped with a full set of modern digital interfaces including DVI-I, HDMI and DisplayPort and does not support the obsolete analog interfaces Composite, S-Video and YPbPr. It doesn’t support CrossFire either – joining two Radeon HD 4550 into one graphics subsystem wouldn’t make sense. With these interfaces on board, the card seems to be optimal for HTPCs that allow to install a full-size graphics card (it can be an ATX-like case, for example the Thermaltake Bach, or a low-profile case with an adapter that turns the PCI Express x16 slot by 90 degrees, for example the Cooler Master Media 260).

The second reference version of Radeon HD 4550 is significantly different from the first one because it uses a half-size PCB.

This solves many problems concerning the installation into small system cases. Oddly enough, this version supports analog interfaces. The DVI-I port is universal and allows to connect both digital and analog sources, so the dedicated D-Sub connector looks redundant here. Well, this connector is attached to the PCB via a cable and won’t be used in a small system case because you need to install an appropriate mounting bracket for that. The mini-DIN port offers the user a wider choice of interfaces, so we won’t criticize the card for having it. Of course, this version of Radeon HD 4550 supports HDMI – by means of an adapter. Its specifications are identical to the full-size version except for the memory amount. The low-profile version has 256 rather than 512 megabytes of memory.

The low-profile PCB is more compact and doesn’t have the room necessary to install a large passive heatsink. Therefore it is equipped with an active cooler. The latter is simple and consists of a small aluminum heatsink with some ribbing and a modest fan. The cooler is covered with a plastic casing.

Considering the simple PCB design of RV710-based solutions, we guess there will soon be many unique versions of such graphics cards on the market.

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