Understanding GDDR5 and GDDR6X for Gamers

GDDR5 and GDDR6X are both members of the GDDR (Graphics Double Data Rate) series, which are specialized memory technologies for GPU. The latter is a upgraded high-end version of the former, with huge leaps in performance, and there are obvious differences in core parameters, technical features and application scenarios. Here is a detailed comparison and introduction:

GDDR5
- Core Parameters: Its operating frequency ranges from 5GHz to 7GHz, the common bus width is 128 – 384bit, and the corresponding typical bandwidth is 200 – 336GB/s. Compared with the previous-generation GDDR3 and GDDR4, it has made great progress in power consumption control. Its operating voltage is reduced to 1.5V (down from 1.8V of GDDR3), and the 55nm manufacturing process also helps reduce chip size and heat generation.
- Key Technical Features: It adopts a DQ parallel dual-bus design, which is equivalent to adding an additional data channel on the basis of GDDR3. This structure enables its theoretical speed to be more than 4 times that of GDDR3. Even a graphics card with a 128-bit bus width can achieve performance exceeding that of a GDDR3 graphics card with a 256-bit bus width through high frequency. In addition, it inherits the 8-bit prefetch technology and supports power management functions, which can balance performance and energy efficiency.
- Typical Applications: As a classic mainstream graphics memory, it was widely used in mid-to-high-end graphics cards from the late 2000s to the mid-2010s. Representative products include NVIDIA GTX 970 and AMD RX 580. It has laid a foundation for the popularity of 1080P gaming and general graphics processing with its high cost performance.
GDDR6X
- Core Parameters: It has a significant improvement in frequency, with an operating frequency of 19 – 23GHz. The bus width is usually 256 – 384bit, and the typical bandwidth can reach 912 – 1008GB/s or more. For example, the NVIDIA RTX 4090 equipped with GDDR6X has a bandwidth of up to 1008GB/s. While improving performance, it also optimizes energy efficiency to a certain extent, with a lower single-task energy consumption (pJ/bit) compared with previous generations.
- Key Technical Features: The biggest highlight is the adoption of PAM4 (Pulse Amplitude Modulation 4) encoding technology. Unlike the traditional PAM2 (NRZ) binary encoding that only transmits 1 bit of data per clock cycle, PAM4 uses 4 different signal levels to transmit 2 bits of data per clock cycle, which directly doubles the data transmission efficiency without doubling the operating frequency. This innovative encoding is the core reason why GDDR6X achieves a breakthrough in bandwidth, but it is more sensitive to external interference and has higher requirements for circuit design and heat dissipation.
- Typical Applications: It is mainly used in flagship graphics cards that pursue top performance. It was first applied to NVIDIA’s Ampere architecture RTX 30 series (such as RTX 3080 and RTX 3090) and later continued to be used in high-end models such as the RTX 4090. It is mainly oriented to scenarios such as 8K ultra-high-definition games, real-time ray tracing, and lightweight AI reasoning, which can meet the huge data throughput requirements of these data-intensive tasks.
Key Differences Between GDDR5 and GDDR6X

Feature	GDDR5	GDDR6X
Frequency	5 – 7GHz	19 – 23GHz
Bandwidth	200 – 336GB/s	912 – 1008GB/s +
Core Technology	DQ parallel dual-bus, 8-bit prefetch	Innovative PAM4 encoding technology
Power Consumption & Heat Dissipation	Low power consumption and heat generation, 1.5V operating voltage	Higher heat generation due to high performance; optimized single-task energy consumption but requires strict heat dissipation solutions
Application Scenarios	Mid-to-high-end graphics cards, suitable for 1080P/2K games and general graphics processing	Flagship gaming graphics cards, suitable for 8K games, real-time ray tracing, AI reasoning and other high-load scenarios
Cost & Popularization	High cost performance and wide popularity	High manufacturing cost, limited to high-end flagship products