One of the big launches this year will be the Haswell-E platform.  It is pretty much common knowledge in hardware discussions that this means Haswell-E, X99 and DDR4 will effectively launch to the consumer on the same day.  One element of that link that we have the fewest leaks and information from is the DRAM side.  I explicitly asked the DRAM manufacturers I have most contact with if they would be showing any DDR4 – either modules, specifications or in action.  Many of them obliged – it helps that a fair number also make SSDs and so Kristian was able to get a few snapshots.  But talking to GeIL at Computex also revealed something a little more interesting: CAS Latencies.

Memory, as I attempt to convey in reviews, is more than just the frequency stated.  There are several sets of subtimings associated with the memory, often divided up into primary subtimings, secondary and tertiary.  The primary ones are the most important, and arguably one of the most important of those is called the CAS Latency, or CL for short.  Memory is usually quoted as a combination of frequency and CL, and in the past it has been easy to compare kits by comparing the results of Frequency divided by CL, such that the kit with the higher result is often the better performing.

Moving from DDR3 to DDR4 means a move from 280-pin to 288-pin connections.  The layout of the modules is slightly different, with the pins being different lengths (notice in the image above how the pins in the middle are longer than those at the edge) in order to help installing memory.  Voltage moves down from 1.5 V to 1.2 V, and processors are expected to support DDR4-2133 by default.

Most manufacturers on the Computex show floor were coy with what sub-timings they will aim for their modules, whereas GeIL had a handy list:

So when GeIL offers below 2133 MHz, I am a little taken aback, because their answer is ‘because some people will use it’.  I hope that the reason they will use it is because the processor will not support above 1600 MHz.  But this list gives that clear indication of CAS Latency between 1600 Mhz and 2400 MHz, with indications that 2666 MHz and 3200 MHz might be more common than we think.

CAS Latency for DDR4 does seem a little down compared to DDR3, though this might be due to the initial batches of ICs coming through.  I remember 2133 C11 being the first 2133 MHz DRAM off of the shelf, but now we can buy 2133 C8 very easily.

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  • Ian Cutress - Friday, June 13, 2014 - link

    Correct. Five years of writing DDR3-2133 and it gets stuck. Updated :)
  • ikjadoon - Sunday, June 22, 2014 - link

    Haha, I understand...actually, when I wrote my comment, I wrote accidentally wrote "DDR3-2133", too, lol.
  • toncij - Friday, June 13, 2014 - link

    So this means we will get DDR4 desktop platforms by end of Q3?
  • extide - Friday, June 13, 2014 - link

    Yeah, if you are going to buy a Haswell-E system. For the "normal" desktop stuff, it won't be until 2016 with Skylake.
  • CaedenV - Friday, June 13, 2014 - link

    I am patiently awaiting that day! Things like DDR4 and new HDD connectivity standards are just about the only reason to upgrade a core system anymore. CPUs are continuing to improve... but the practicality of their improvements outside of competitive overclocking and extreme production environments is questionable at best. SSDs continue to get faster, but without new connection standards there are diminishing returns. PCIe v4 will be overkill by the time it is released, but it will allow PCIex8 graphics slots to be used without bottleneck to allow PCIe lanes to be freed up for other uses (thunderbolt, HDDs, etc.).
    It is weird to not have any real want to upgrade my PC after 3 years. Hopefully Skylake will offer something worth upgrading to.
  • jdub_06 - Monday, November 3, 2014 - link

    im still rocking a i7 1366, 12gb ddr3 it with a real hardware raid controller and 4ssds (ocz vertex 3) + 3hdds and semi recent graphics card (amd 7980)...

    the mobo and cpu are 5 years old now and i still dont see much of a reason to update. ill probably end up going through one more gfx card in before i do (i update about every 2 generations).

    sure its not the fastest rig around anymore but 5 years later it still outdoes some mid level offerings and feels fast day to day.

    even when I do retire it, it will probably make a nice hypervisor system for a few linux servers.
  • toncij - Friday, June 13, 2014 - link

    I would love to be able to buy something worth buying... I could use 4 more real cores, I need more SATA2 connections, I need cheaper PCIE SSDs too tho, but seems nothing worth buying is coming soon. If Haswell-E will offer 8/16 @4GHz with turbo @4,4 (like refresh), native SATA2 of at least 6 and DDR4 faster than 2,4GHz... it may be worth buying.
  • celestialgrave - Friday, June 13, 2014 - link

    Look at the history of ddr memory, every advance lowers the voltage and raises the CL. I still have a Barton system running Hyper X DDR2 at CL 4.
  • ViRGE - Friday, June 13, 2014 - link

    If you compensate for clockspeed increases, what you'll find is that latency on an absolute (temporal) basis isn't much changed from before. It still takes so many nanoseconds to fetch data. We're now just able to fetch more at once.
  • Revolution11 - Friday, June 13, 2014 - link

    Also, if you keep in mind the voltage required, RAM has become more efficient over time, trading latency for reduced voltage. Obviously if you pump up the voltage on a IC, latency can be reduced. ShieTar explains it better and with formulas, read his post.

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