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DDR5 memory is on its way, twice as fast as DDR4

pcworld.com

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Re: DDR5 memory is on its way, twice as fast as DDR4

#21

Post by fiedzia »

refrigerator wrote: post #5

Would the equivalent amount of DDR5 actually feel any different to DDR4 to the end user? It seems like hardware is getting better but basic software (web browser etc) is getting more complicated/bloated at the same rate, so things don't actually feel 10x faster than they did a few years ago.

>Would the equivalent amount of DDR5 actually feel any different to DDR4 to the end user?

Most likely not at all. Browser speed has more to do with network speed and browser/website design than your hardware. Browsers and websites still make poor use of multiple cores, and making sites performing well is a never ending chase between designers adding more ads, images and visual effects, browsers trying to figure out tricks to make coping with that possible and developers implementing those tricks.

Re: DDR5 memory is on its way, twice as fast as DDR4

#24

Post by axelfontaine »

TazeTSchnitzel wrote: post #19

Are there applications which will see significant benefit from a new generation of DRAM, or higher speeds? Games, for instance, seem to see only very small performance differences from changing RAM speeds.

In-memory datastores like Redis. They are also the ones who benefit the most from faster XMP DDR4.

Re: DDR5 memory is on its way, twice as fast as DDR4

#25

Post by Retric »

trey-jones wrote: post #6

So, it's been a while since I tinkered with hardware, but I'm making the blind assumption that although the bus speed is twice as fast as DDR4, there is also twice the read latency, as has always been the case with DDR memory, meaning the net read latency improvement is basically nil. Of course we expect every generation of Double Data Rate memory to double the data rate. But it's always been a bit misleading to say…

Latency is limited by the speed of electricity which is a large fraction of the speed of light, so unless you move DDR closer to the CPU it physically can't get 2x as fast... ever. light speed * 0.951 (electricity) / 2 (round trip) / 2 feet (CPU to furthest RAM chip along a wire) ~= 250 million cycles per second.

However, cache is now huge. So, it's latency is usually less of an issue than sequential reads/writes and total size.

Re: DDR5 memory is on its way, twice as fast as DDR4

#26

Post by plopz »

sp332 wrote: post #14

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.

When you see RAM listed at 4200, its the same as the 2133 but the sticks have been tested to be able to overclock to 4200.

Re: DDR5 memory is on its way, twice as fast as DDR4

#27

Post by pmalynin »

phkahler wrote: post #18
sp332 wrote: post #14

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.

Above 8 gigs per module you're going to need buffered ram. Check in the ECC section.

Re: DDR5 memory is on its way, twice as fast as DDR4

#28

Post by Retric »

petra wrote: post #17
dom0 wrote: post #15

Earlier quoted context omitted.

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 ?

Heat, RAM puts out a lot more than you might think. That said, for low power devices like cellphones you can use different packaging and cut latency.

Also, AMD for example uses stacked ram (HBM), but that needs very special packaging and active cooling. http://www.amd.com/en-us/innovations/software-technologies/h... https://en.wikipedia.org/wiki/High_Bandwidth_Memory

Re: DDR5 memory is on its way, twice as fast as DDR4

#29

Post by phire »

mikhailt wrote: post #23
akmittal wrote: post #2

Most laptops shipped this year still has DDR3/LPDDR3 RAM

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.

Re: DDR5 memory is on its way, twice as fast as DDR4

#30

Post by sp332 »

plopz wrote: post #26
sp332 wrote: post #14

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.

When you see RAM listed at 4200, its the same as the 2133 but the sticks have been tested to be able to overclock to 4200.

Right, but it's only an "overclock" because the official spec only goes to 2133. And that means that compatibility is very hit-or-miss. It could benefit from being more standardized.
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