JEDEC Reveals Key Aspects of DDR4
by Kristian Vättö on August 23, 2011 2:01 PM ESTDDR3 made its debut in mid-2007 when Intel released P35 chipset with support for DDR3. Today nearly all desktop, mobile and server platforms support DDR3. iSuppli estimates that DDR3 will account for roughly 90% of DRAM sales this year. However, the next generation DRAM technology is already just around the corner and JEDEC is scheduled to release the full DDR4 specification next year. Yesterday, JEDEC published some of the specifications of the upcoming DDR4 technology.
First and foremost, DDR4 will concentrate on performance and power consumption. The latter is achieved by lowering the voltage to 1.2V, compared to DDR3's 1.5V (although there are DDR3 modules with lower or higher voltage but 1.5V is the standard for most). The performance gain is achieved by increasing the frequency and DDR4 will start from 1600MHz. It's likely that we will see 1866MHz or 2133MHz modules as the standard though, considering that DDR3 went straight for 1066MHz as well, even though a 800MHz specification existed too. The projected maximum speed for DDR4 is 3200MHz but then again, DDR3's maximum is 1600MHz, yet 2133MHz DDR3 modules are available. We will likely see even higher bandwidth DDR4 modules in the future. JEDEC lists the prefetch buffer for DDR4 as 8n, which is identical to DDR3. If this ends up being the case the bulk of the performance increase will be due to higher operating frequencies enabled through more advanced signaling.
The higher operating frequencies come at the expense of some serialization of the interface. The SDRAM memory interface remains one of the last parallel buses in modern PCs. While it doesn't look like DDR4 will change that, we have heard reports of the new memory standard moving to a point-to-point protocol. In other words: one DDR4 module per memory channel. Note that JEDEC hasn't confirmed this will officially make it into the DDR4 spec.
Source: JEDEC
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EJ257 - Tuesday, August 23, 2011 - link
If that is the case, does each chip or combination of chips service one single SP on the GPU specifically? If that chip goes bad, does that SP now perform more poorly because it just lost some of it's RAM?Ryan Smith - Tuesday, August 23, 2011 - link
No. A memory crossbar means that any unit has access to any region of RAM. And if a chip goes bad the video card is rendered inoperable; it has no way of compensating for a missing/damaged memory module.fhaddad78 - Tuesday, August 23, 2011 - link
Ryan Smith.... Are you from the Matrix?silverblue - Wednesday, August 24, 2011 - link
What, by having the surname Smith?Beenthere - Tuesday, August 23, 2011 - link
The current 1.35V DDR3 is good. Higher frequencies don't add any tangible performance benefit with the current bandwidth so it really matters not if it's 1600 or 2000 MHz. AMD's new Zambezi will allow the use of LV DDR3 with a default speed of 1866 MHz.FaaR - Wednesday, August 24, 2011 - link
Buddy, I'm glad we have you here with us, telling us what we don't need, now or in the future. :-PClearly this is a standard that's supposed to last for a number of years ahead of where we are now. With integrated graphics processors in our CPUs, bandwidth will become a more and more pressing concern as time goes on.
Ethaniel - Tuesday, August 23, 2011 - link
... not compatible with DDR3 When you think about retrocompatibility, they don´t.Andrew.a.cunningham - Tuesday, August 23, 2011 - link
It makes sense, really - it's hard to build a memory controller with support for a standard that doesn't exist yet. :-)cosmoanu87 - Wednesday, September 28, 2011 - link
More like they want us to dump old stuff and buy new modules :D what better way than to make DDR3 incompatible? :)fhaddad78 - Tuesday, August 23, 2011 - link
Why is that person holding the memory module like that? I thought it's not a good idea to put your fingers on the contact end of the chip. Clearly this violates Article 15, Section 9, Paragraph 37, Line 12 of the DDR4 handling specification.That person is "holding it wrong."