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JEDEC officially specs DDR4 RAM up to 2133 MHz. But manufacturers seem to have left this far behind already, with Corsair and G.Skill shipping modules at 4200 MHz. I don't see why JEDEC doesn't just add a few more rows to the table of official speeds. The only real advantage for a new spec is to bump the density.
And they better have, because Intel already standardized 2400 as the recommended speed for Skylake.
Is DDR4 memory a major bottleneck in systems today?
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Because LPDDR4 wasn't available in sufficient quantities or not supported by the platform SkyLake only supported LPDDR3 and the current KabyLake SKUs also do not support LPDDR4.
Is LPDDR3 what is also referred to as DDR3L, or is that different?
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That's due to integrating the memory controller onto the CPU, you can't switch memory controller to use a newer spec, you're stuck with whatever the CPU supports.
These laptops ship with broadwell/skylake/kabby lake processors, which support both DDR-3L and DDR4 memory. But for price/power-budget reasons, they ship with the DDR-3L option.
JEDEC officially specs DDR4 RAM up to 2133 MHz. But manufacturers seem to have left this far behind already, with Corsair and G.Skill shipping modules at 4200 MHz. I don't see why JEDEC doesn't just add a few more rows to the table of official speeds. The only real advantage for a new spec is to bump the density.
>> The only real advantage for a new spec is to bump the density. And DDR4 can apparently support 128GB per module. Those apparently exist, but you can't find even a 32GB at Newegg.
http://thememoryguy.com/samsungs-colossal-128gb-dimm/
But that was the end of 2015, we are into 2017 and i have yet to see this again on the market. And they are likely very expensive.
I really hope DDR5 bumps the spec to 512GB rather then 256GB. Unfortunately the DDR memory / GB prices is actually on the rise. The only thing i could see changes in the market is when all the Fabs from China goes online in 2018, and China continue to pour in tens of billions of money in it.
Is DDR4 memory a major bottleneck in systems today?
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https://en.wikipedia.org/wiki/CAS_latency First word latency: DDR3 SDRAM 6.37ns = 1/156,985,871 of a second.
tCL is (very) roughly the RAM equivalent of sequential access time. I'm talking random access time, tRAS, which includes closing the last row (precharging the diff amps) and opening the next (waiting for the amps to stabilize). It's called Random Access Memory, so I think it's more fair to judge it by its random access time.
DDR is not really setup for random access, because it's setup for talking to L2/L3 cache not registers. tRAS ~= tCL + tRCD + tRP which kind of but not exactly exactly what you want for random access.
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That's not a very accurate analogy, since sequential reads do improve. CAS latency is one limiting factor on random reads, which has been constant / only slightly improving for a very long time; significant improvements last happened here around with DDR and SDR (i.e. 20 years ago). This is a central reason why the cache size per thread has not changed much in the last 20 years (beside of course fabbing/yield limits)…
If cas latency haven't changed for 20 years, and the memory wall in general being a huge pain, does anybody know why didn't some sort of 2.5D memory(even using low-resolution lithography and carriers cheaper than silicon), haven't entered the market ?
How much difference is there between GDDR and regular DDR? I think that GDDR runs at higher voltages and temps than regular DDR. I'm assuming if GDDR5 is available, then it's kind of inevitable that regular DDR 5 would be coming at some point.
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>> The only real advantage for a new spec is to bump the density. And DDR4 can apparently support 128GB per module. Those apparently exist, but you can't find even a 32GB at Newegg.
Above 8 gigs per module you're going to need buffered ram. Check in the ECC section.