What is PC2700 DDR SDRAM ?
Thursday, January 31, 2002
Intel official DDR chipset launched
Jan 21, 2002, less than two weeks into Intel official launched of a new chipset supporting Double Data rate (DDR) DRAMs operating at 266 MHz for PC2100, there is already a growing speculation about the prospects for the next generation of 333 MHz DDR chips for PC2700.
What is PC2700 ?
DDR also known as Double Data Rate SDRAM memory technology is a revolutionary new technology derived from the mature SDRAM technology. The secrets behind DDR memory high performance architecture is its capability to perform two data read/write operations in one clock cycle – therefore providing twice the throughput of SDRAM. If you have not read the previous article regarding PC2400 DDR Memory –
DDR memory currently supports memory bus speeds of either 100MHz or 133MHz, equivalent to Data Rate of 200 and 266Mhz respectively. Newer and faster memory bus speed such as 166Mhz (Data Rate 333Mhz) and the DDRII 200Mhz (Data Rate 400Mhz) are presently under consideration by JEDEC.
Lately, there have been many enquires into the availability of PC2700 even when PC2100 have not emerged as the main stream memory yet. Offically, Intel have launched the new 2.2Ghz P4 with DDR i845D chipset on Jan 7, 2002 and DDR memory should eventually replace PC133 SDRAM very quickly.
For those who have not read the previous article on PC2400, this is how PC2700 should be interpreted. PC2700 describes the memory transfer rate of 2700 MB/sec (2.7 GB/sec) on a 64-bit bus rather than its Clock speed Mhz.
My first stop is to find out if JEDEC have approved the PC2700 standards for the 184pin DIMM. After researching JEDEC website at www.jedec.org, I have not found a single PC2700 DIMM reference design guide released, indicating that the guidelines are still in the “Work in Progress” stages. But on another note, only the 200pin DDR SODIMM reference guide could be found.
What make up a JEDEC Reference design guide?
Firstly, JEDEC is a committee of a collective team of industry leaders which gather monthly to formulate, decide and dictate the standards for new emerging semiconductor components. Once JEDEC have approved the detail specs, a reference design guide, it will published a set of guidelines for memory module designer to use as an aid when designing a DDR memory module. Click Here to access Jedec
Usually JEDEC will release the following reference guide-lines which consist of:
- Architecture (Block diagram of module)
- Component details (Pin assignments, DC Characteristics and SPD component specification)
- DIMM PCB – Details (Reference design, PCB Gerber files)
- DIMM wiring details
- SPD definition
- Product label guide
- Mechanical Specification
Read the previous article on how to identify DDR module Click here
Since no PC2700 reference guide can be found at JEDEC website, it would indicate that PC2700 memory module will take at least another six to nine months before the process of validation and testing by different chipset, PC system and memory module manufacturer. As far as the timeframe for the release of the PC2700 184pin DIMM reference design guide – we estimate that by the first quarter of 2002 – the JEDEC committee would have the details ready for release.
Behind the scenes, the delay in the release of PC2700 standards, is attributed by a packaging hurdle. There is debate over whether the higher frequency chips should move to new chip-scale packaging (BGA) instead of remaining in traditional thin small outline packages (TSOP).
Nanya Semiconductor have released technical information on the PC2700 using TSOP chips Click Here
Click here for a 256MB DDR Datasheet
SIS 333 DDR Chipset
Recently SIS, a Taiwanese chipset manufacturer have announced the availability of a DDR 333Mhz chipset (SiS645 and SiS745), supporting PC2700 DDR memory with a list of validated PC2700 DIMM module published. You can check Click here for more information on the Non JEDEC standard validated PC2700.
VIA Technology 333 DDR Chipset
With the introduction of Via Technologies - Athlon/Duron-based KT333 chip set next month, all three Taiwanese core logic vendors, VIA ,SIS & Acer Lab will have silicon that supports the faster 333-MHz memory by the end of the year.
Motherboard manufacturer also predict 30 percent to 40 percent of their designs will enable DDR333 by the end of the 2002. More importantly, however, they also acknowledge that few Large PC OEMs, system integrators or clone makers will choose it, settling instead for cheaper DDR 200/266Mhz with acceptable performance.
Motherboard problem affecting 333Mhz Launched
Read about the problems facing 333Mz DIMM launched Click here to read article
Some sample pictures of PC2700 DIMM
Presently, the following unofficial PC2700 DDR memory are available for sale, ask your local memory dealer for pricing details.
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