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An unofficial guide to DDR400 or PC3200 DDR SDRAM

Tuesday, July 9, 2002

In the latest volley over next-generation DRAM performance, PC chipset makers and memory chip makers have been announcing a so-called PC3200 double-data-rate device that will compete head-on with the Direct Rambus architecture.

Samsung release 400Mhz chip
Samsung the world ''s leading supplier of advanced memory technology, recently announced that it is first to ship Double-Data-Rate 400Mbps SDRAM (DDR400) modules in 128MB, 256MB and 512MB densities.

The 400Mbps (200MHz) DDR devices are ideal for use as PC system main memory, offering three times the performance of Single-Data-Rate PC 133 SDRAM and 50 percent more bandwidth than mainstream DDR266.

Early this year, Samsung was first to deliver engineering samples of DDR400 to major PC chipset companies, including NVIDIA, SIS and VIA. The devices have received positive feedback and leading-edge motherboard chipsets supporting DDR400 will soon be available through distribution.

"With Samsung ''s DDR400, chipset manufacturers and their customers are the real winners as they benefit from this extremely high-performance memory," said Tom Quinn, Samsung Semiconductor ''''''''s vice president of marketing. "Samsung is totally committed to serving our customers by being first-to-market with leading-edge DDR SDRAM memory products."

In reality – are there really any demand for the so-call DDR PC3200 ? How did PC3200 nomenclature surfaced ?

Will it ever be a standard ?

DDR-II standard
JEDEC announced last year that the industry standard body had approved the preliminary spec for the next generation DDR-II memory chip, which is expected to be in production by end 2003.

As part of the preliminary spec, JEDEC approved 400Mhz and 533MHz DDR chips , and DDR memory modules would carry the PC3200 nomenclature for a 3.2Gbyte/s bandwidth using the 400MHz chip, and PC4300, with a bandwidth of 4.3GBytes/s for the 533MHz chip.

This is how PC3200 should be interpreted. PC3200 describes the memory ''s transfer rate of 3200 MB/sec (3.2 GB/sec) on a 64-bit memory bus rather than its MHz speed.

Apparently PCxxxx rating is not just for the FSB of the memory Bus. It is the rating standard that involves Data-transfer speed on the Memory BUS between the CPU and Memory when running any application. At the time of this article, only PC1600, PC2100 & PC2700 have been finalized as a industry standard.

PC1600 = DDR 200MHz Data-rate (100 Clk x 2) 1.6Gb/Sec
PC2100 = DDR 266MHz Data-rate (133 Clk x 2) 2.1Gb/Sec
PC2400 = DDR 300MHz Date-rate (150 Clk x 2) 2.4Gb/Sec
PC2700 = DDR 333MHz Data-rate (166 Clk x 2) 2.7Gb/Sec
PC3000 = DDR 366MHz Data-rate (183 Clk x 2) 3.0Gb/Sec
PC3200 = DDR 400MHz Data-rate (200 Clk x 2) 3.2Gb/Sec

PC4300 = DDR 533MHz Data-rate (266 Clk x 2) 4.3Gb/Sec

PC3200 Nomenclature
Early this year Jedec, later confirmed that DDR-II would skip 400Mhz and start at 533Mhz , but somehow the chip manufacturer have decided – that they had to sell memory chips capable of running at the highest speed, therefore the PC3200 nomenclature which was reserved for DDR-II , became a DDR-I nomenclature.

Jedec have announced recently that DDR-I will support a maximum data-rate frequency of 333Mhz or PC2700.The PC2700 standards are still pending Jedec approval.

SIS have recently launched a new PC chipset which supports double-data-rate (DDR) DRAMs operating at 333 MHz (SIS645 and SIS745) capable of over-clocking to 400Mhz and VIA Technology have made similar announcement , there is growing speculation about the prospects for 400-MHz chips over the next few months. Only a handful of motherboard manufacturers are building boards which support 400Mhz data-rate, since Intel roadmap does not plan to have a chipset to support 400Mhz.

DDR400 Picture
So if you are out shopping for PC3200 memory which should work at a lower frequency, the following are some sample pictures of PC3200 DIMM memory:

PC3200 256MB DDR DIMM using TSOP

PC3200 256MB DDR DIMM using TinyBGA

OCZ Technology
PC3200 256MB DDR DIMM using TSOP

PC3200 128MB DDR DIMM using TSOP

PC3200 128MB DDR DIMM using TSOP

To read the previous article regarding PC2700 DDR Memory –
Click Here

To read the previous article regarding PC2400 DDR Memory –
Click Here

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By: DocMemory
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