DuhSesame

mfryd said:

melgross said:

Ok, so the writer gets it wrong, as so many others have when it comes to the M series RAM packaging. One would think that’s this simple thing would be well understood by now. So let me make it very clear - the RAM is NOT on the chip. It is NOT “in the CPU itself”. As we should all know by now, it’s in two packages soldered to the substrate, which is the small board the the SoC is itself soldered to. The lines from Apple’s fabric, which everything on the chip is connected with, extend to that substrate, to the RAM chips. Therefore, the RAM chips are separate from the SoC, and certainly not in the CPU itself. As we also know, Apple offers several different levels of RAM for each M series they sell. That means that there is no limit to their ability to decide how much RAM they can offer, up to the number of memory lines that can be brought out. This is no different from any traditional computer. Every CPU and memory controller has a limit as to how much RAM can be used. So, it seems to me that Apple could, if it wanted to, have sockets for those RAM packages, which add no latency, and would allow exchangeable RAM packages. Apple would just have to extend the maximum number of memory lines out to the socket. How many would get used would depend on the amount of RAM in the package. That’s nothing new. That’s how it’s done. Yes, under that scheme you would have to remove a smaller RAM package when getting a larger one, but that's also normal. The iMac had limited RAM slots and we used to do that all the time. Apple could also add an extra two sockets, in addition to the RAM that comes with the machine. So possibly there would be two packages soldered to the substrate, and two more sockets for RAM expansion. Remember that Apple sometimes does something a specific way, not because that’s the way it has to be done, but because they decided that this was the way they were going to do it. We don’t know where Apple is going with this in the future. It’s possible that the M2, which is really just a bump from the M1, is something to fill in the time while we’re waiting for the M3, which with the 3nm process it’s being built on, is expected to be more than just another bump in performance. Perhaps an extended RAM capability is part of that.

Actually, moving the memory further away from the CPU does add latency.  Every foot of wire adds about a nanosecond of delay.

Then there is the issue of how many wires you run.  When the memory is physically close to the CPU you can run more wires from the memory to the CPU, this allows you to get data to/from the CPU faster.   It's not practical to run a large number of wires to a socket that might be a foot or more of cable run away.  That means you transfer less data in each clock cycle.

Generally socketed memory is on an external bus.  This lets various peripherals directly access memory.  The bus arbitration also adds overhead.


Traditional CPUs try to overcome these memory bottlenecks by using multiple levels of cache.  This can provide a memory bandwidth performance boost for chunks of recently accessed memory.  However, tasks that use more memory than will fit in the cache, may not benefit from these techniques.

Apples "System on a Chip" design really does allow much higher memory bandwidth.   Socketing the memory really would reduce performance.

cloudguy said:

saarek said:

I hope this isn’t true.

I’m hoping for a true performance king that humiliates AMD & Intel and sets the bar in terms of performance. Primarily GPU based upgrades over the M1 wouldn’t be the big step up in the true “Pro” Macs over the current M1 that I was hoping for.

With all due respect why do you believe that this is even possible? As I have stated numerous times, the idea that ARM is inherently superior to x86 was wishful thinking. If it were true, ARM would have more than 3% of the server market. As I have also stated, most of the benchmarking was skewed: it only compared the M1 to the Intel chips that it replaced in macOS devices. Those were mostly 2 and 4 core "mobile" chips. They were also outdated chips: 9th and 10th gen. There were already 11th gen Intel chips on the market when the M1 Macs were introduced.

 Yet all the M1 crushes Intel who is now doomed! "benchmarks" ignored them just as they ignored how comparing 2 and 4 core "mobile" chips to a chip with 4 performance + 4 efficiency cores never made any sense. They just took Apple's claim - unsubstantiated by any data - that the M1 was faster than "80% of Windows PCs" and ran with it. Also, 4Q this year we are going to see 10nm big.LITTLE chips from Intel followed by 5nm Zen 4 chips - Athlon architecture, not big.LITTLE - chips from AMD. Intel hasn't started hyping their 12th gen chips yet, but AMD is claiming that their Zen 4 chips will have up to 40% performance gains over their current chips. 

Thinking that Apple was going to dominate Intel and AMD in PCs the way they dominate Qualcomm and Samsung in mobile never made any sense. Especially if it was based on the superiority of ARM because Qualcomm and Samsung make ARM chips too. Apple versus Qualcomm was "ARM CPU with laptop performance versus ARM CPU with embedded appliance performance." Fine. Apple versus Intel and AMD: ARM CPU with laptop performance versus x86 CPUs that power 97% of the world's servers. A totally different ballgame.