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PCB Design

The PCB of the Radeon X1950 XTX is a slightly modified PCB of the Radeon X1900 XTX, which is not a surprise considering that both these cards are based around the same GPU.

 

There seems to be no difference between the cards, but you can spot it on closer inspection. The power circuitries are different in the first place. A Volterra VT1103 controller is responsible for power on the Radeon X1800 and X1900, but the Radeon X1950 XTX comes with a Volterra VT1105 that has a rectangular rather than square packaging. So, the wiring of this part of the PCB was changed accordingly. This in its turn provoked other changes that concerned the placement of various smaller elements, capacitors, coils, etc. Some power circuit elements are not even soldered on the new card due to the reduced power consumption of GDDR4. Particularly, one power MOSFET with an accompanying inductance coil Pulse PA0511 is missing at the bottom of the PCB and a number of other elements are absent, too. You can see the same on the reverse side of the mainboard: some elements that used to be included into the memory power circuit are not installed now. Moreover, the fan connector, a 4-pin one now, has moved to the back part of the PCB.

There are fewer differences in that part of the PCB where the GPU resides, yet you can spot some: the contact pad with an unclear purpose (perhaps to install an additional TMDS transmitter) that was present in the top left corner of all Radeon X1800 and X1900 cards is now missing. There are more points of difference on the reverse side of the PCB, but all of them are due to lack of certain elements that used to be installed on the Radeon X1900 XTX. The Rage Theater chip that endows the card with VIVO functionality is in its customary place. There’s not much use from it today, but extra functionality is always welcome.

The marking on the GPU chip remained intact: there is no “plus” in the core code-name. The R580 chip on our sample of the card was manufactured on the 21st week of 2006, i.e. at the end of May. The core is clocked at 650MHz in 3D mode, just as on the Radeon X1900 XTX. This frequency is lowered to 500MHz in 2D mode. The die packaging is equipped with a metal frame for protection. This is an appropriate measure considering the large die area and the massive cooling system.

It was difficult to read the marking on the memory chips as it had been virtually erased by the heat-conductive pads, yet we managed to do that. There are eight Samsung K4U52324QE-BC09 chips of GDDR4 memory on the card. According to the specification, these 512Mb chips are designed as 16Mx32 and work at 1.8V voltage.

The BC09 suffix denotes an access time of 0.91 nanoseconds. This access time means that the chip is rated to work at a frequency of 1100 (2200) MHz, yet its consumption current is only 1130mA at the maximum (in Burst mode), which gives a power consumption of about 2W per chip. The fastest GDDR3 memory chip (K4J5324QC-BJ11), which works at 2.0V voltage and at 900 (1800) MHz frequency, consumes a current of 1180mA and has a power consumption of 2.36W. So, GDDR4 is obviously better than the older memory type in terms of power consumption, especially considering its higher operating frequency. Moreover, the BC09-suffixed chip is the slowest in the K4U52324QE series whereas the fastest BC07-suffixed chip is capable of working at 1400 (2800) MHz, consuming this same 2.36W.

The memory frequency is somewhat reduced below the rated one on the Radeon X1950 XTX card and is 1000 (2000) MHz. Accessed across a 256-bit memory bus, it provides a memory bandwidth of 64GB/s, which is the new record for consumer 3D graphics hardware. The memory frequency is lowered to 600 (1200) MHz in 2D mode.

 
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