Embedded Engineers these days work on different memories which includes Flash, EEPROM and RAM. RAM is a temporary memory and we cannot imagine an embedded product without RAM. Such is the dominance and extensive usage this kind of memory has. Whether it be speed, cost RAM is the which helps complex embedded products performance. The important advantage is less latency. Now DDR is one category of RAM which uses Dynamic Memory. In DDR itself there are several categories which can be used for less demanding applications and performance demanding products like the Graphics cards. GDDR is such memory which is used for graphics cards and DDR for other embedded applications. Lets us look at the differences between then in brief:
- The first and foremost thing is the power supply. Comparing DDR4 and GDDR4, DDR4 operates on 1.2V while GDDR4 needs 1.5V rail.
- The first difference is the data bus width. When we talk about the performance, one factor is the rate at which data can be accessed. This points us to the data bus width and the major difference between the DDR and GDDR is the data bus width. For example DDR3 interfaces 64-bit but the same GDDR3 can use up to 384-bit data bus
- GDDR has lower thermal requirements than DDR. This indicates the heat dissipation and the power requirements are lesser for GDDR
- GDDR owing to it's bandwidth can raise a request and receive data within that clock cycle. Check the datasheet of DDR5 for the timing and detailed pin out description.
- While the DDR4 is now becoming a common use in embedded systems and DDR5 is work in progress, Graphics cards already have the GDDR6 specifications defined
- While the DDR has a single clock for the DATA, ADDRESS and COMMAND signals, GDDR has clock for ADDRESS, CLOCK and 2 differential clocks for DATA
- Latency is a critical factor for RAM. While for common embedded applications which use DDR, latency is very important. While for GDDR, along with latency, Band-Width is very important.
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