GDDR

Graphics Double Data Rate, short GDDR is the additional designation for DDR memory, which is designed for graphics cards.

Types

The following types of GDDR been or are being developed:

(G ) DDR

GDDR is based on memory chips according to DDR SDRAM standard. In this first generation, the voltage of VDD and VDDQ (chips with 4 & 5 ns) is 2.5 V. With clock speeds 166-400 MHz and Read latencies of 3, 4 and 5 clock cycles, a maximum data throughput of 25, 6 GB / s with 256 -bit connection achieved. GDDR works like the DDR SDRAM with a dual - prefetch.

GDDR2

GDDR2 presented as a further development of GDDR an unpopular intermediate step is, there were indeed reached higher clock frequencies, but GDDR2 had problems with the waste heat produced at high frequencies. Only on a few graphics cards like the GeForce FX 5800 Ultra GDDR2 was used with the maximum clock frequency of 500 MHz, most manufacturers use a maximum of 400 MHz or less. Criteria were the VDD / VDDQ voltages of 2.5 / 1.8 volts, clock rates of 400 MHz (2.5 ns) to 500 MHz (2.0 ns) and read latencies 5-7 clock cycles. In order for a maximum data throughput of 32 GB / s with 256 -bit connection has been reached.

GDDR3

GDDR3 is a modification of DDR2 SDRAM for use on graphics cards. As in (G ) DDR was optimized by means of lower access times and changed Read latencies on high memory clock. DDR3 operates as DDR2 SDRAM having a VDD / VDDQ voltage of 1.8 V. If the clock rates of 700 ( 1.4 ns) to 1300 MHz (0.77 ns) and read latencies 5-9 clock cycles is a maximum data throughput of 83.2 GB / s with 256 -bit connection possible. GDDR3 works like the DDR2 SDRAM with a quad - prefetch.

Although GDDR3 was designed by ATI, it came for the first time in March 2004 at the NVIDIA GeForce FX 5700 Ultra and then at the Geforce 6800 Ultra used. For ATI even the memory was installed for the first time with the Radeon X800. Other well-known products, which will use GDDR3, are Sony's PlayStation 3 (256 MB for the graphics card ) and Microsoft's Xbox 360 (512 MB ​​will be used simultaneously by the CPU and GPU).

GDDR4

GDDR4 uses an eight- prefetch so it is based on a DDR3 - like technique. The doubling of the number of prefetch bits compared to GDDR3 allows higher transfer rates at lower clock rate of memory cells. As a result, the supply voltage could be reduced. The start of series production of GDDR4 was carried out at Samsung on July 5, 2006. Hynix has GDDR4 chips with up to 1.6 GHz on. In combination with a 256 -bit memory interface, so a memory bandwidth of up to 102.4 GB / s can be achieved. The first use of GDDR4 memory on a graphics card was the Radeon X1950 XTX ATI, which was specified with a memory clock of 1 GHz. Another use of GDDR4 memory took place at the Radeon HD 3870th However, GDDR4 could never prevail on a broad front, probably because GDDR3 achieved by manufacturing progress over 1 GHz.

GDDR5

GDDR5 chips have a memory size from 512 Mbit, at speeds in the range 5-7 Gb / s At 2.5 GHz clock frequency ( and a latency of 0.4 ns) provides GDDR5 per connector and second 5 Gb of data, which adds in the usual x32 chips on 20 GByte / s GPUs with 256 data lines reach for the memory interface with eight 2.5 GHz GDDR5 chips connected in parallel ( 0.4 ns ) that is 160 GB / s The first graphics card in the GDDR5 was used, the ATI Radeon HD 4870 that the first version was about 512 MB ​​GDDR5 memory (0.56 ns @ 1.8 GHz and 115.2 GB / s) is available. The large-scale production began in the first half of 2008. Qimonda has the first GDDR5 SDRAM chips shipped in large quantities, while Hynix introduced the first pattern. Samsung has announced GDDR5 memory with reduced power supply voltage of 1.35V. Sony announced on February 20, 2013, the PlayStation 4 with 8 GB system memory GDDR5 ( 256-bit memory interface and 176 GB / s).

GDDR6

The semiconductor manufacturer AMD and the JEDEC group working on new GDDR6 standard. First Graphics Cards with GDDR6 memory to appear in 2014.

Sources

• Memory module