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GeForceFX 5700U GDDR3

GDDR3 graphics memory is ready for the masses, and NVIDIA shows us that it can easily be adapted to even their current video cards. Are there any benefits to it? Many.

Introduction:

GDDR3 memory technology was actually developed by JEDEC in collaboration with ATI as an open standard. They developed it openly so that everyone would be able to adopt it. Even though ATI had a big hand in creating this technology NVIDIA is actually the first to implement it on a current video card as well as their new GeForce 6800Ultra.

The Gruesome Facts:

Right now there are more DDR1 memory chips in use on graphics cards than GDDR2 memory chips. Even though GDDR2 has been out for more than a year its adaptation has been slow. Currently the only graphics cards from NVIDIA that utilize GDDR2 are the short lived GeForceFX 5800Ultra and the current GeForceFX 5700Ultra. On ATI’s side the only graphics card to use GDDR2 is the Radeon 9800Pro 256MB video card. The reason for this lack of adaptation is the fact that GDDR2 memory requires the same amount of VDD Voltage (2.5v) as DDR1. VDD is the voltage which feeds the input buffers and core logic of a memory chip. Because GDDR2 runs internally at the same voltage as DDR1 and also runs at higher clock speeds the heat given off is very high compared to DDR1. GDDR2 does have the advantage with VDDQ Voltage being at 1.8v versus DDR1’s VDDQ of 2.5v. VDDQ is the voltage which feeds the output buffers of the memory chip. Because the GeForceFX 5800Ultra and 5700Ultra are run at very high memory speeds GDDR2 was needed to achieve those clock speeds. There is something better than GDDR2 though, and that is GDDR3.

GDDR3 Tech Goodness:

GDDR3 has a VDD Voltage of 1.8v-2.0v and a VDDQ of 1.8v-2.0v which is much less than GDDR2’s 2.5v VDD. The reason for the variation, 1.8v-2.0v, is because DRAM manufacturers may set the voltage differently as we can see below.

Samsung’s GDDR3 product list can be seen here. As you can see at the top under Features it says 2.0v is the power supply for device operation and I/O interface (VDD and VDDQ). What is most impressive is their K4J55323QF-GC12 chip capable of 800MHz operation. For a detailed data sheet on Samsung’s 256Mbit GDDR3 memory click here.

Micron’s GDDR3 product list can be seen here. Their data sheet indicates VDD and VDDQ of 1.8v. Their current highest offering is MT44H8M32F2FW-14 at up to 700MHz.

Here is Hynix’s 256Mbit GDDR3 product lineup. Their data sheet indicates VDD and VDDQ of 1.8v. Their highest offering is their HY5RS573225F-12 chip capable of 800MHz.

There are more GDDR3 advantages than just lower voltages though. There are also some key signaling differences between GDDR2 and GDDR3. GDDR2’s strobe signal is a Bi-directional & Differential (DQS, /DQS) while GDDR3’s strobe signal has been upgraded to Uni Directional & Single-ended (RDQS, WDQS). Without getting to technical what this means is that a separate read and write data strobe has implemented allowing for a quicker read to write turn around. The receiver type has also been upgraded from a Push Pull method on GDDR2 to a Pseudo Open-Drain method on GDDR3. GDDR3 also has a new hardware reset capability which is a first in GDDR technology. Basically what this lets the chip do is perform a hardware reset of its data to wipe it clean and start receiving new data if needed. GDDR3 also has a one step power up process whereas GDDR2 required a two-step process which starts from a low frequency below 100MHz to ensure DRAM initialization then it changes the frequency to high. One of the biggest improvements in GDDR3 is that it now has on-die termination which will allow for higher frequencies. Lower power requirements with greater performance are always a plus.

If you’d like to read more about GDDR3 there are many resources open to you. Micron has some good technical notes on GDDR3 Functionality and On-Die Termination. Samsung has a PDF on key differences between GDDR2 and GDDR3 here. You can also always hit up JEDEC for some info.

GeForceFX 5700U:

Here is what a reference GeForceFX 5700Ultra with GDDR3 memory looks like. As you can see above the PCB layout is exactly like the BFG 5700Ultra with GDDR2 memory. The only difference is simply that it is using GDDR3 modules.