Radeon HD 4870 1GB card design

Not surprisingly, the Radeon HD 4870 1GB looks just like its 512MB brother at a first glance. Both cards feature the same dual-slot cooler complete with a variable speed fan that’s quiet when you’d expect it to be and spins up when it gets a little hot under the collar.

There are two six-pin power connectors on the end of the card – both are required for the card to operate. AMD said that despite the increased memory, there is no additional burden on the power supply – the maximum TDP is still quoted at 160W.

The PCI bracket is kitted out in exactly the same way as well – there are two DVI ports that are both dual-link capable and support dual, simultaneous HDCP-protected streams at up to 2,560 x 1,600. In between the two dual-link digital connections, there’s a TV-out connector for almost all of your analogue connection needs; it supports component, S-video and composite video via additional connectors supplied by the board partner.

The chip also natively supports HDMI and DisplayPort, giving board vendors the opportunity to customise their designs, and like the Radeon HD 2000 and 3000 series cards, there is support for audio. This time around though, AMD has beefed up the RV770 audio controller’s capabilities and it can now support 7.1 high definition sound with bitrates of up to 6.144Mb/sec at 192KHz using all of the popular audio formats either via native HDMI or a DVI-to-HDMI dongle (supplied by the board partner).

AMD ATI Radeon HD 4870 1GB AMD ATI Radeon HD 4870 1GB - card design AMD ATI Radeon HD 4870 1GB AMD ATI Radeon HD 4870 1GB - card design
Click to enlarge

Upon a closer inspection after removing the heatsink, there’s nothing obviously different on the new card. There are a few serial numbers that have changed, but that appears to be about it – the PCB is still approximately 224mm long. The power circuitry on the card also looks to be relatively unchanged as well.

Voltage regulation is handled by the Vitec 59PR9853 multi-phase inductor and two Pulse PA0511 VRMs – none of these chips are cooled by the heatsink, but interestingly there are a couple of unused solder points next to the Vitec inductor, meaning there’s room for a larger module should one of AMD’s partners want to introduce a Radeon HD 4870 with significantly higher clock speeds for example.

AMD ATI Radeon HD 4870 1GB AMD ATI Radeon HD 4870 1GB - card design AMD ATI Radeon HD 4870 1GB AMD ATI Radeon HD 4870 1GB - card design
AMD ATI Radeon HD 4870 1GB AMD ATI Radeon HD 4870 1GB - card design AMD ATI Radeon HD 4870 1GB AMD ATI Radeon HD 4870 1GB - card design
Radeon HD 4870 1GB (left), Radeon HD 4870 512MB (right) - Click to enlarge

The Vitec inductor, and the three MOSFETs that accompany it, is responsible for regulating voltage to the RV770 die, while the two Pulse VRMs (and two remaining MOSFETs) are responsible for controlling the GDDR5 memory voltage. The MOSFETs require cooling and are covered with thermal pads that come into contact with the card’s cooling solution. Without the additional cooling, the ‘FETs are likely to pop because of the high temperatures at which they operate.

Of course, there is at least one difference between these cards and that’s the memory used. Interestingly, instead of using 16 of the 512Mb Qimonda GDDR5 DRAMs used on the Radeon HD 4870, AMD has used eight Hynix 1,024Mb GDDR5 memory chips on the 4870 1GB, meaning there’s next-to-no additional engineering required to get this board working. What’s more, these are the same chips as those found on the Radeon HD 4870 X2, which also has 1GB of memory per GPU.
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