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PCB Design, Specs, Cooling System

MSI’s card uses the reference PCB design developed especially for the Radeon HD 3650. The PCB looks sophisticated due to the dense component placement, yet it is only because the PCB is small. The card is very compact and can be easily installed into any system case save for low-profile systems that don’t have a riser to turn the PCI Express x16 slot by 90 degrees.


The power circuit is very simple, the RV635 requiring even less power than the RV670. The two-phase GPU voltage regulator is based on an uPI uP6201BQ controller (reference samples of Radeon HD 3870/3850 have an uP6201AQ controller). Each phase has two power transistors but the design allows installing three transistors per each phase. This improvement will hardly be necessary for RV635-based cards, though. A separate regulator based on an uP6101BSA chip (we know it from Radeon HD 3870/3850, too) is responsible for the memory chips. The card lacks an external power connector and does not actually need one. By our estimates, its power consumption is 30-40W. The power section of the PCI Express can provide far more than this.

There are 8 chips of GDDR3 memory on the card, four on the face side and four on the reverse side of the PCB. It is impossible to put all the chips on the face side of such a small PCB. These Qimonda HYB18H512321BF-10 chips have a capacity of 512Mbit (16Mbit x 32), a voltage of 2.0V, and a rated frequency of 1000 (2000) MHz. The memory frequency is 800 (1600) MHz, the same as on the reference Radeon HD 3650. It means there is some room for increasing the memory frequency considering the specs of the memory chips. On the other hand, the 128-bit memory bus limits the bandwidth, which is only 25.6GBps by default. Even if the memory is overclocked to its rated frequency of 1000 (2000) MHz, the resulting bandwidth will only be 32GBps which is a very modest number for a modern graphics card.

The GPU die is very small as you could guess considering the RV630 specs and the 55nm tech process. The marking on the core doesn’t tell us anything valuable save for the manufacturing date, which is the sixth week of 2008 (February 3 – 9). The GPU frequency is higher than the reference card’s: 750MHz against 725MHz of the Radeon HD 3650 and 800MHz of the ATI Radeon HD 2600 XT GDDR4 (see this news story for details). This modest overclocking can hardly produce a notable effect in games and help outperform the predecessor.

As noted above, the RV635 has the same amount of functional subunits as its predecessor. The GPU incorporates 120 ALUs grouped into 24 superscalar execution modules with 5 ALUs in each (4 ALUs can execute simple instructions like MAD while the fifth has a more complex architecture and can execute transcendental instructions like SIN, COS, LOG, EXP, etc). This architecture has its pros and cons as we have described in our previous graphics card reviews concerning the ATI Radeon HD series.

Besides the computing part, the core has two large texture processors roughly equivalent to 8 TMUs and one raster processor which is comparable to 4 classic ROPs. That’s more than modest in comparison with Nvidia’s G94, let alone G92 even in cut-down configurations. We cannot expect the Radeon HD 3650 to set any performance records. The GPU also features a second-generation UVD video-processor and an audio core that supports audio-over-HDMI.

Belonging to the low-end sector, the Radeon HD 3650 has two standard CrossFire connectors for building CrossFireX configurations. This feature has little practical value, though. The card is also equipped with two dual-link DVI-I ports with support of resolutions up to 2560x1500 and HDMI (with an adapter), and a universal mini-DIN port for analog video output.

The R3650-T2D512-OC has a non-reference cooler. It is a rather simple thing, resembling Thermaltake’s Orb or Zalman’s models with a radial placement of the heatsink ribs and a fan nestled in the center to blow in every direction. The heatsink is made from aluminum. It wouldn’t be wise to use expensive copper in such a cheap product with such a low level of heat dissipation. The fan has a 3-wire connection although the connector on the PCB has 4 pins and supports PWM-based speed management.

The heatsink is surrounded with an air-directing aluminum frame that also serves as a decoration. It is embellished with an MSI logo and a picture of an android girl. The cooler is fastened to the PCB with four spring-loaded nuts that are put on the heatsink’s threaded mounting poles. The nuts are fragile – you should be cautious with them if you want to replace the thermal interface or replace the cooler. There is an X-shaped back-plate that prevents the PCB from bending although this is hardly necessary due to the low weight of the cooler.

This cooler seems to be even redundant for a Radeon HD 3650 yet its surplus performance can be used to reduce the level of noise. The next section will tell you how noisy it really is.

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