Sapphire HD 4870 X2 2048 MB Review 205

Sapphire HD 4870 X2 2048 MB Review

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Sapphire Logo

Today is the launch of the long anticipated AMD Radeon HD 4870 X2. This card features two RV770 graphics processors on a single PCB. The RV770 has been used on the HD 4850 and HD 4870 in the past. Another product announced today is the Radeon HD 4850 X2. The HD 4870 X2 uses GDDR5 memory, while the 4850 variant uses GDDR3. Compared to the single GPU designs, both X2 cards feature twice the available video memory per GPU. The HD 4870 X2 has 2 GB of GDDR5 - 1 GB per GPU. AMD is positioning their HD 4870 X2 as "the fastest graphics card on the planet" - which is reflected in the price of $549.
Sapphire's HD 4870 X2 follows the AMD reference design specifications to the letter, the only difference is the Sapphire sticker on the cooler.

One novel feature of the HD 4870 X2 is that it has an additional direct-GPU-to-GPU interconnect called CrossFire Sideport (XSP). The XSP offers an additional 5 GB/s interlink bandwidth between the GPUs but is not enabled at this time. Yes, you read correctly. The official reason why the XSP is disabled at this time is because that much bandwidth is not required with current applications and it will be enabled at some point in the future via driver update.
One major advantage of the XSP that I see is that transfers between the GPUs would have a lower latency. The Gen2 PCI-E bridge will certainly be fast, but it will take a short time to process the incoming data and send it out to the other GPU (<140 ns). With the XSP's point-to-point interlink this delay is eliminated. So my speculation is that AMD is working on using the XSP feature but the driver support simply doesn't work as intended at this time.

HD 3850
HD 3870
9600 GT
8800 GT
9800 GT
HD 4850
9800 GTX
9800 GTX+
8800 GTX
GTX 260
HD 4870
HD 4850 X2
GTX 280
HD 4870 X2
Shader units 320320641121128001281281281928002x 8002402x 800
ROPs16161616161616162428162x 16322x 16
GPURV670RV670G94G92G92RV770G92G92G80GT200RV7702x RV770GT2002x RV770
Transistors666M 666M505M 754M754M 956M754M 754M 681M 1400M 956M2x 956M1400M 2x 956M
Memory Size256 MB 512 MB 512 MB 512 MB 512 MB 512 MB 512 MB512 MB768 MB896 MB512 MB 2x 1024 MB 1024 MB2x 1024 MB
Memory Bus Width 256 bit 256 bit 256 bit 256 bit 256 bit 256 bit 256 bit 256 bit 384 bit 448 bit 256 bit 2x 256 bit 512 bit 2x 256 bit
Core Clock670 MHz 777 MHz 650 MHz 600 MHz 600 MHz 625 MHz 675 MHz 738 MHz 575 MHz 576 MHz 750 MHz 625 MHz 602 MHz 750 MHz
Memory Clock828 MHz 1126 MHz 900 MHz 900 MHz 900 MHz 993 MHz 1100 MHz 1100 MHz 900 MHz 999 MHz 900 MHz 1000 MHz 1107 MHz 900 MHz
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May 17th, 2022 00:58 EDT change timezone

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