When memory channel is 64bits wide using differential signaling the pcb designer must keep wire lengths identical within few millimeters for 128 lines. Half of which are coming much closer to memory socket than the other half.
End result is that the wires that leave from the ”bottom” of the chip need to do extra curves to have roughly same electrical distance. This requires space on pcb. Or additional layers, which cost money.
At those sizes RAM certainly seems to eat more of the invest than CPUs, but I wonder if that's also true for energy consumption: Just how much engineering goes into "energy proportional RAM usage"
Memory is cheaper. But capacities also go up. Geeze, I remember when one 1K board of RAM for my S-100 buss computer cost close to $400 (in 1976 dollars!). How much would 256GB RAM cost at that price?
Not always true, depends on what you are running, in many cases AMD's solution looks better and better, except for maybe the powerscaling of infinity fabric.
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iwod - Saturday, October 20, 2018 - link
Sigh, when are we going to get cheaper memory?yuhong - Sunday, October 21, 2018 - link
It must get cheaper for 16Gbit DDR4 to catch on.CrazyElf - Sunday, October 21, 2018 - link
Possibly once China begins large scale production of DRAM. NAND prices might fall even more if that happens as well.rpg1966 - Sunday, October 21, 2018 - link
Why are the recent dual-height DIMMs required, when the chips can be packed as efficiently as these into what appears to be a much lower height?zepi - Sunday, October 21, 2018 - link
When memory channel is 64bits wide using differential signaling the pcb designer must keep wire lengths identical within few millimeters for 128 lines. Half of which are coming much closer to memory socket than the other half.End result is that the wires that leave from the ”bottom” of the chip need to do extra curves to have roughly same electrical distance. This requires space on pcb. Or additional layers, which cost money.
rpg1966 - Monday, October 22, 2018 - link
Thanks zepi. Compared to those DIMMs, what's different about these 256GB RDIMMs - the bus width, the number of lines, the signalling type...?abufrejoval - Sunday, October 21, 2018 - link
At those sizes RAM certainly seems to eat more of the invest than CPUs, but I wonder if that's also true for energy consumption: Just how much engineering goes into "energy proportional RAM usage"melgross - Sunday, October 21, 2018 - link
Memory is cheaper. But capacities also go up. Geeze, I remember when one 1K board of RAM for my S-100 buss computer cost close to $400 (in 1976 dollars!). How much would 256GB RAM cost at that price?Chaotic42 - Sunday, October 21, 2018 - link
$102.4 Billion, though I'm guessing you could get a volume discount.rpg1966 - Monday, October 22, 2018 - link
I had an S-100 box connected to my Exidy Sorcerer. Those were the days!mjz_5 - Monday, October 22, 2018 - link
I bought 32GB of DDR3 ram for 150$ 5 years ago. 32GB of ram now is 300!.. that doesn't make sensemsroadkill612 - Sunday, October 21, 2018 - link
Would it be true that a server needing as much memory as possible, is also likely to need as many cores as possible?Epyc would win on both counts I presume.
Zoolook - Monday, October 22, 2018 - link
Not always true, depends on what you are running, in many cases AMD's solution looks better and better, except for maybe the powerscaling of infinity fabric.Diji1 - Monday, October 22, 2018 - link
No one needs more than 640K surely?shwick - Thursday, October 25, 2018 - link
take this, add a battery, no more hard drivecarcakes - Sunday, February 23, 2020 - link
Triple sockets DDR4 vs 24TB optane memory vs 8GB hbm2