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Closer Look: Design and PCB

The 512MB version of ATI RADEON X800 XL doesn’t differ that much from the 256MB version, as you may have expected it to. Take a look yourselves:



All the major design differences have to do with the location of additional memory chips. Since the 512MB version is equipped with 16 GDDR3 chips instead of 8, this resulted into a considerably bigger amount of various tiny electronic components on the PCB around the memory chips. Also the number of stripes grew up significantly, too.

Here I have to point out a few special things. RADEON X800 XL is designed on 8- and 10-layer PCBs. Some manufacturers are preparing simpler 6-layer PCBs for RADEON X800 XL and they are currently going through some testing. Since there is only one manufacturer using 10-layer PCB design, according to ATI, then we dare suppose that the RADEON X800 XL 512MB is based on an 8-layer PCB. Some stripes leading to the memory chips are laid out inside the PCB, that is why it is impossible to use 6-layer PCB for the 512MB RADEON X800 XL solution because of the signal termination problems.


Other than that the PCB layout of two RADEON X800 XL versions is very similar. Even the location of many individual components and the PCB size are identical. RADEON X800 XL 512MB is just a little bit longer because of the technological lug at the back of the PCB, which doesn’t carry any electronic components or stripes.

The voltage regulators of the cards are also almost the same except for a couple of chips for additional power supply for the 512MB version. In fact, we were surprised to see it there, as ATI claimed that the power consumption of the new 512MB RADEON X800 XL would be only 5-7% higher than that of the regular RADEON X800 XL graphics card. We carried out a small experiment and disconnected the additional power supply from the card, so that it had to be happy with the power it could get through the PCI Express connector only. The graphics card didn’t react to it in any way and continued working just fine at the same clock frequency without the external power supply. So, I would assume that ATI Technologies provided this additional power supply line to ensure higher stability of the device, and not because they were concerned with its power consumption level.

Since this graphics card belongs to the top price category, the presence of RageTheater chip implementing VIVO support and two DVI connectors are also quite justified. One of these connectors is implemented by the transmitter built into the R430 core, while the other one – by the stand alone Silicon Image SiI1162 chip. You can actually see this chip on all contemporary ATI RADEON graphics cards featuring two DVI-I outs.

Now that the cooling system has been successfully removed we can see the VPU:

The marking suggests that this piece was manufactured during week 48 of last year. The chip is equipped with a metal frame typical of all top ATI chips, which protects the fragile edges of the die from physical damage. We also removed the layer of thermal paste from one of the memory chips:

This is a classical Samsung K4J55323QF chip with 2.0ns access time. It is very often used on high-end and mainstream graphics cards today. The card is equipped with the total of 16 chips 256Mbit each, which makes 512MB. Samsung and Infineon already have 512Mbit GDDR3 chips at their disposal, so with these ones they could do with only 8 chips per card thus simplifying the PCB layout significantly. However, these chips are still pretty expensive and are not that widely spread. Therefore ATI decided to go for better value 256Mbit chips that were widely available when they designed their RADEON X800 XL 512MB.

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