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PCB Design and Specifications

Although the PCB of the Sapphire Toxic HD 4850 card is azure, not a typical color for ATI, its wiring copies the reference card precisely. The PCB design is good, simple and inexpensive, so there is no need to develop a completely new PCB for the Radeon HD 4850 especially as Sapphire is the largest contract partner of AMD’s graphics department.

The card has a simple two-phase GPU voltage regulator based on an uP6201 controller. The power transistors are cooled with a small individual heatsink on this card because it uses a nonstandard cooler. The memory voltage regulator has one phase and is based on an uP6101 chip. The PCB carries one 6-pin PCI Express 1.0 power connector with a load capacity of 75W. As we found out in our earlier tests, this connector fully satisfies the power requirements of the Radeon HD 4850. This card being pre-overclocked, we are going to re-measure its power draw, but we think it will only consume 5-7W more than the reference card due to the modest growth of the GPU and memory frequencies.

The card is equipped with GDDR3 memory in chips from Samsung rather than Qimonda as on the reference Radeon HD 4850. The eight K4J52324QH-HJ08 chips with a capacity of 512MB (16Mb x 32) are rated for a frequency of 1200 (2400) MHz and make up a standard memory bank with a total capacity of 512 megabytes accessed across a 256-bit bus. The card’s memory frequency is increased to 1100 (2200) MHz relative to the reference Radeon HD 4850, ensuring an increase in bandwidth from 64 to 70.4GBps. That’s a useful addition because the RV770 can digest a much bigger stream of data as our tests of the Radeon HD 4870 showed. Each memory chip has a small individual heatsink fastened with a gluey thermal pad.

The GPU has a standard configuration with 160 superscalar execution modules with five ALUs in each, 10 texture processors equivalent to 40 TMUs, and four raster back-ends equivalent to 16 ordinary rasterization processors. The core frequency is increased from the reference card’s 625MHz to 675MHz. This is far below the core frequency of the Radeon HD 4870, so we expect a performance growth of 10% or something in games. You can also try to overclock the card further. The Toxic HD 4850 is a good card for such experiments thanks to its advanced Zalman VF900 cooler.

The card has two dual-link DVI-I ports, a universal 7-pin mini-DIN port for analog video output, and two CrossFireX connectors for building a graphics subsystem out of four such cards. The card also supports audio-over-HDMI, including high-definition formats described in the HDMI 1.3 standard, thanks to the new-generation audio core integrated into the RV770.

So, the Toxic HD 4850 doesn’t differ much from the reference card. It just has an azure-colored PCB, a more advanced cooler, and slightly higher GPU and memory frequencies. On the other hand, this card looks quite original in comparison with the precise copies of the reference card offered by other makers.

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