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With regards to RAM price I never understood the following: A 16GB RAM stick has 16*8=128 billion bits, with 1 transistor per bit, thats still 128B, yet its sup
by torginus 3mo ago
With regards to RAM price I never understood the following: A 16GB RAM stick has 16*8=128 billion bits, with 1 transistor per bit, thats still 128B, yet its supposed to cost like $60 before the price hikes? In contrast, a 5090 GPU was $2000 (true it has RAM, but you're paying for the GPU ASIC really, I guess the rest of the GPU was less than $500), it had 93B transistors.
GPU transistors are smaller due to the more advanced process node (cost per transistor metrics aren't really clear, if they improve on advanced node or not, but I'd say they get cheaper as they get smaller, as technology costs are amortized).
I'm sure both RAM and logic use a process that is quite similar in both inputs and manufacturing steps. So while RAM is a commodity product, this insane price difference didn't make any sense.
So I guess when those fundamental inputs become a constraint, it would make sense for $/transistor move closer for both, which is a massive hike for RAM.
- ismaVQ 3mo agonewer process node are smaller but very expensive compared to mature ones, each wafer from TSMC latest process is costly and with lower yield due to GPU large die size (+700mm2 compared to around 60mm2 per DRAM die)
- Lomlioto 3mo agoA GPU Transistor is a lot more complicated than a RAM transistor and the size of these are quite different too. Bleeding edge vs. a known process with know machines and written off machines. Also you calculate in the machine cost and R&D. RAM hiked because the demand spiked and these companies are now in power. Before apple and other companies told them the prices and had hardly any money for investment.
- mschuster91 3mo ago> So while RAM is a commodity product, this insane price difference didn't make any sense. Supply and demand coupled with the fact that a RAM fab can't (trivially) output compute chips, and vice versa, a compute fab can't output RAM. It's two completely different supply chains.
- rmu09 3mo agoThe thing that defines performance of DRAM is AFAIK the capacitor of the bit cells and not the transistor driving it. And also AFAIK the process to create those capacitors is quite unique to DRAM, so you can't just go and use a "logic" process unchanged and produce DRAMs.
- adastra22 3mo agoWhy would you expect smaller transistors to be cheaper?
- jeffbee 3mo agoThat is what Moore's Law said.
- xandrius 3mo agoNot really a law though.
- jeffbee 3mo agoNobody voted for it, that's true. But since reality held closely to it for decades right up to the present, it's reasonable to believe that transistors get smaller and cheaper as time passes.
- tliltocatl 3mo ago"Moore's law" is a marketing gimmick. The real physical law that held for decades is Dennard scaling, which stopped to apply already in 2006 once transistors got too small so short channel effects and gate leakage kicked in.
- jeffbee 3mo agoDennard scaling hit a wall but Moore's Law did not. Worth considering why. One of these is physical and the other is economic.
- torginus 3mo agoBecause you are paying for silicon, and processes, not transistors. Wafers have a certain cost, and litographic processes can illuminate a certain X mm2 of dies in an hour. If a transistor gets smaller, more of them fit in a certain area. Granted the machines that make them become more expensive, but that's capital expenditure, which gets amortized as time goes on. So there are two forces here working against each other.
- rcxdude 3mo agoChip fabrication processes are not fungible: GPUs and CPUs might be made on roughly the same process, but DRAM is not (flash is a different process again, as is power electronics, analog electronics, MEMS, etc. And even within those broader categories there are different variations). While there are some overlaps in machines and techniques, a fab set up for one cannot generally switch to the other, and the economics of each process can also be drastically different.
- joha4270 3mo agoYou're not the first person to say so (and I don't mean to dispute it), but I have never been able to find a clear answer for /why/ those processes are incompatible. Is it built in different silicon, is it physical steps that's incompatible (ie its actually incompatible), is it different physical preparations that needs to be made (making it economically infeasible to combine) I cannot help but wonder, even if the answer doesn't change anything in my life.
- malfist 3mo ago[flagged]
- kjs3 3mo agoOr, you could look at your peer answers where people very much do provide a non hand-wave answers. Chip fabrication isn't undergrad philosophy; there are well understood reasons for why things are done if you care to find and understand them. And there are stakes in the millions or billions of US$ for getting them wrong.
- jahnu 3mo agohttps://www.reddit.com/r/Semiconductors/comments/r1dqmw/how_memory_and_microprocessors_differ_in/hlycuk8/ https://www.reddit.com/r/Semiconductors/comments/r1dqmw/how_... A Reddit user explains a bit here.
- wolfi1 3mo agofrom my basic understanding, memory is much easier to produce then logic chips like GPUs and CPUs, they don't need that many photolithographic layers. while it could be possible to produce memory in fabs for CPUs (though not really desirable in regard to costs) the other way round is more difficult
- gloryjulio 3mo agoRAM is a commodity. It has much less moat to prevent competitions. When the rams flood the market that's when the bubble ends, until the next cycle arrives. Processors are much harder to design and commoditize.
- WmWsjA6B29B4nfk 3mo agoOn top of everything said, 5090 die size is 10x than typical DDR5 die size. One RAM module is 8-16 dies, so you do get more silicon in the end, but larger dies are extremely expensive to produce due to sharply decreasing yields.
- NooneAtAll3 3mo agoRAM is literally copy-paste of the same circuit over and over, you're trying to compare cost to produce million AK-47 with 1 carrier and cost per transistor stopped decreasing at ~20-30nm, now small nodes are targetting energy efficiency (and thus performance, since heat is the main limiter)
- fc417fc802 3mo agoConsider that the R&D cost of the GPU (>>> RAM) must be amortized across total units sold (<<< RAM).