31–40 of 74 posts
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.
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.
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…
My suspicion is that amplifying the differential voltages produced by femtocoulombs of charge at 100% reliability is a harder problem than moving the DRAM chips closer to the CPU, and that speed-of-light has gotten the blame in "pop architecture" due to sloppy overgeneralization.
2*2 feet is long for a memory bus, but it's partially cancelled
out by the high velocity factor (sorry, "speed of electricity")
of 0.951 in parent's calculations. Instead, I'm going with 0.5*2
feet at a velocity factor of 0.5 for a 2ns roundtrip propagation delay.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.
Games are a special breed of application since they delegate a lot of work to the GPU and often are GPU-bound, not CPU-bound. Other workloads often end up with the CPU waiting for memory accesses. The most obvious example, besides stream-processing, would be garbage-collected languages. Simply scanning the heap will benefit from all the memory bandwidth it can get. Even if speeds don't improve perceptibly because the…
Yeah, and the GPU (at least a dedicated one) has its own VRAM, so accesses for which RAM speed would otherwise be important end up relying on VRAM speed, I assume.
Earlier quoted context omitted.
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…
I keep hearing this, but it doesn't jibe with the RAM timings I see. tRAS is usually 50ns or so, and propagation delay is 2ns or so (see below). What gives? My suspicion is that amplifying the differential voltages produced by femtocoulombs of charge at 100% reliability is a harder problem than moving the DRAM chips closer to the CPU, and that speed-of-light has gotten the blame in "pop architecture" due to sloppy ov…
First word latency: DDR3 SDRAM 6.37ns = 1/156,985,871 of a second.
Earlier quoted context omitted.
I keep hearing this, but it doesn't jibe with the RAM timings I see. tRAS is usually 50ns or so, and propagation delay is 2ns or so (see below). What gives? My suspicion is that amplifying the differential voltages produced by femtocoulombs of charge at 100% reliability is a harder problem than moving the DRAM chips closer to the CPU, and that speed-of-light has gotten the blame in "pop architecture" due to sloppy ov…
https://en.wikipedia.org/wiki/CAS_latency First word latency: DDR3 SDRAM 6.37ns = 1/156,985,871 of a second.
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.
Do you have an SSD yet? A good one? Computers with good SSDs and not too much bloatware (relevant on Windows) do feel faster to me than computers used to be. I think people can get nostalgic accidentally and overestimate how fast things were in the past. I remember multi-minute loads for games on my Commodore 64. I remember multi-minute Windows 3.1 bootups. I remember watching a JPEG progressively creep in on the ear…
I've recently switched from 8GB MBA to 16GB MBP and to be honest, I'm not sure I've noticed any more speed above what's to be expected from any brand new machine before it gets bogged down with shit. My MBA used to be able to handle multiple big programs running in the background - 2 of the Adobe suite + Chrome + small stuff, so I haven't felt much use for the extra juice day-to-day, though I imagine the RAM is useful for video editing etc.
Most laptops shipped this year still has DDR3/LPDDR3 RAM
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.
Earlier quoted context omitted.
>> 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.