Closer Look at Radeon HD 5850 vs. Radeon HD 5870

PCB Design and Functionality

Our ATI Radeon HD 5850 graphics card is a copy of the reference sample. It came to us in OEM packaging without any accessories. We will discuss our HD 5850 (left) in comparison with an HD 5870 (right).

The face sides of the cards are almost identical except that the Radeon HD 5870 is 38 millimeters longer, being actually the longest graphics card of today. Both devices are 100 millimeters wide and 37 millimeters thick, blocking the neighboring expansion slot on the mainboard.

The Radeon HD 5850 does not have a metallic cover on its reverse side as the HD 5870 has:

We guess the cover is no good for cooling and the Radeon HD 5850 feels better for not having it. There is a red plastic piece on the cooler casing of the cards which has slits on the right for exhausting hot air.

The card’s mounting bracket also has vent slits and a full set of modern interfaces: two DVI-I ports, HDMI and DisplayPort.

At the opposite end there are two 6-pin connectors for additional power (these are located at the top of the PCB on the Radeon HD 5870). According to its specs, the peak power draw of the Radeon HD 5850 is no higher than 170W (as opposed to the Radeon HD 5870’s 188 watts). A 550W or better power supply is recommended for computers with this graphics card (we guess this is a bit of an overstatement). The power draw plummets to a mere 27W in 2D mode.

Now let’s take a look at both cards with their coolers removed.

As opposed to the Radeon HD 5870 which has a 4-phase GPU voltage regulator, the Radeon HD 5850 has only three phases and a seat for an uninstalled fourth phase.

The RV870 chip of our Radeon HD 5850 is dated the 35th week of this year and has a simplified marking in comparison with the Radeon HD 5870’s GPU manufactured on the 33rd week of 2009.

The RV870 is manufactured on 40nm technology and has fewer shader processors (1440 against 1600) and texture processors (72 against 80) in the Radeon HD 5850 than in the HD 5870. The junior model’s GPU is clocked at a lower frequency (725MHz against the Radeon HD 5870’s 850MHz) and lower voltage (1.087V against 1.149V). In 2D mode the GPU frequency of each card is dropped to 157MHz and its voltage is reduced to 0.949V. Coupled with a reduced memory frequency, this helps achieve a substantial economy. The 334 sq. mm GPU die is turned by 45 degrees relative to the protective metallic frame. So if you are installing an alternative cooling system, you have to make sure its GPU-contacting piece is larger than 26 millimeters in both width and length. Otherwise, the GPU die won’t be covered fully.

Both cards are equipped with eight GDDR5 memory chips located on the face side of the PCB. The chips were manufactured by Samsung and are the same for both cards.

They are marked as K4G10325FE-HC04 and have an access time of 0.4 nanoseconds, which corresponds to a theoretical frequency of 5000MHz. However, the memory frequency of the Radeon HD 5850 is set at 4000MHz, giving some hope for good overclocking. The Radeon HD 5870 has a memory frequency of 4800MHz. The memory bus is 256 bits wide.

Here is a summary of the cards’ specs.