4 ms·

Random Idea: If we think about it, computers today have a limited number of RAM expansion slots, even on server motherboards, the number of RAM slots might be l

Random Idea: If we think about it, computers today have a limited number of RAM expansion slots, even on server motherboards, the number of RAM slots might be limited to say, 32. So, I'm wondering (and maybe something like this already exists) what if RAM could be placed at the end of a high-speed serial cable of some sort. Like Firewire, Ethernet, Fast USB, or some kind of LVDS high-speed data serial cable... Now, this RAM (because it would allow for long cable sizes, because we'd like to connect more of it to a PC, and thus the serial cable speed would be a bit reduced due to length) would not be intended as System RAM -- but more like a faster-than-SSD hard drive -- although perhaps it could be used as System RAM, just as slightly slower System RAM... Note To Future Self: Look into the various ways that RAM can be connected via high-speed serial links (also, in the future, such links might include optical fiber...). So, high speed serial links AND optical fiber...

GrumpyYoungMan 6y ago
It's been tried but never achieved any significant commercial success. https://en.wikipedia.org/wiki/Texas_Memory_Systems https://en.wikipedia.org/wiki/Texas_Memory_Systems https://en.wikipedia.org/wiki/I-RAM https://en.wikipedia.org/wiki/I-RAM https://en.wikipedia.org/wiki/HyperOs_HyperDrive https://en.wikipedia.org/wiki/HyperOs_HyperDrive
garaetjjte 6y ago
> Look into the various ways that RAM can be connected via high-speed serial links https://www.devever.net/~hl/omi https://www.devever.net/~hl/omi
meepmorp 6y ago
Look at CXL for what industry is doing in that general direction, and Gen-Z which kinda sorta extends the general idea beyond a box/rack with pooled accelerators and memory Edit: and IBM’s CAPI
- splistud 6y ago
  This plus NAND is where we're headed I believe
azornathogron 6y ago
It's not precisely what you're talking about, but you might be interested in Remote DMA: https://en.m.wikipedia.org/wiki/Remote_direct_memory_access https://en.m.wikipedia.org/wiki/Remote_direct_memory_access
t0mbstone 6y ago
The problem with putting RAM at the end of a cable is that RAM latency is highly dependent on distance from the CPU. Assuming RAM is 2 inches away from the cpu, and assuming the CPU is operating at 3 ghz, you are looking at 3 billion round trips per second over the distance of 2 inches, or a grand total of 12 billion inches of wire being crossed per second. Electric signals are limited by the speed of light, though. In a vacuum, light travels at 299,792,458 meters per second, or 11,802,852,677 (11 billion) inches per second. Do you see the bottleneck?
- mechagodzilla 6y ago
  That's not really how CPUs / RAM have worked since the 1980s. The CPU doesn't operate synchronously out of RAM, fetching data on each clock cycle. It operates from a hierarchical series of on-die caches, with only the L1 cache (typically a few 10s of kilobytes at most) operating close to how you describe. Logic on the CPU will send a series of commands to the RAM (along with data if it's a write), and there will be many commands 'in-flight' around the system at any given time, to hide the relatively high latencies involved (many 10s of nanoseconds). The actual propagation delay (around ~1 nanosecond/foot for cables) barely figures into it. Even the cables can have many 'bits' in flight at a time on them, and typically each 'direction' of the link forwards a clock along with the data (or it's embedded in the data stream) to avoid messy synchronization issues.
- peter_d_sherman 6y ago
  I do see the bottleneck! But, short of having a "how to subvert the speed of light" discussion, which would be exceedingly long (and probably unproductive!) -- you've given me an idea! Yes, you are correct that the speed of electrical propagation is limited, and does limit things! We're completely agreed there! OK, so here's my idea! F--- the electrical cable entirely! So, we have Quantum computers, Quantum bits, and all sorts of research on how to compute things with them, all kinds of professors and papers and companies and venture capital all researching how to do Quantum Computation... Well, I say F--- all of that! (In a polite, friendly, "yes your work is really genius and I acknowledge all of your brilliant contributions kind of way!"). Here's the grail! The grail of Quantum is NOT Quantum Computation -- but rather Quantum Communication! In other words, get rid of the damn electrical cable, and figure out a way to do that communication with a pair of connected-at-a-distance Quantum bits; that is -- Quantum Communication! In other words, Quantum Communication -- should replace wires and busses of all sorts, serial, parallel, electrical, light, what-have-you. That's the damn grail!... (pardon my language!) Not Quantum Computing!!! (brilliant though it is, I am not trying to knock it in any way, far from, quite the opposite!) Quantum Communication -- replacing wires and busses of all sorts, serial, parallel, electrical, light -- would be the Holy Grail -- of being able to build bigger computers (like imagine close-to-infinite RAM -- on one motherboard! Close-to-infinite RAM! Well, it would be off that motherboard... but Quantum Communication, if it were available, would, for all intensive purposes, make that RAM so connected, would have the net effect -- of physically existing on the motherboard, even though in actuality it would not be so!) So, to answer your question... YES, I DO SEE THE BOTTLENECK! But... equal-and-oppositely... Do you see my point?
simplyinfinity 6y ago
This is where Optane comes in. Faster than SSD, but larger than RAM: https://www.youtube.com/watch?v=cwy4ujt0qHM https://www.youtube.com/watch?v=cwy4ujt0qHM https://youtu.be/uHAfTty9UWY?t=263 https://youtu.be/uHAfTty9UWY?t=263
ksec 6y ago
> used as System RAM, just as slightly slower System RAM Intel Optane DIMM and Intel Optane SSD. Although Micron is selling their "Optane" Fab and Intel has yet to announce if they intend to buy it. >such links might include optical fiber Intel has been working on this for many years, Silicon Photonics and the goal is to have Compute, Memory and Storage in different "box" or even "Racks". >can be connected via high-speed serial links IBM OpenCAPI and OMI. Which allows up to 5PB of memory ( No more Big Data crap ) , and if I remember correctly with additional 10ns latency.
- dharmab 6y ago
  > Although Micron is selling their "Optane" Fab and Intel has yet to announce if they intend to buy it. I have several close friends working at that fab and I am astounded that Micron is both still in business and hasn't caused a chemical disaster in Lehi yet. It's a fantastically mismanaged and unsafe workplace.

GrumpyYoungMan 6y ago

It's been tried but never achieved any significant commercial success. https://en.wikipedia.org/wiki/Texas_Memory_Systems https://en.wikipedia.org/wiki/Texas_Memory_Systems https://en.wikipedia.org/wiki/I-RAM https://en.wikipedia.org/wiki/I-RAM https://en.wikipedia.org/wiki/HyperOs_HyperDrive https://en.wikipedia.org/wiki/HyperOs_HyperDrive

garaetjjte 6y ago

> Look into the various ways that RAM can be connected via high-speed serial links https://www.devever.net/~hl/omi https://www.devever.net/~hl/omi

meepmorp 6y ago

Look at CXL for what industry is doing in that general direction, and Gen-Z which kinda sorta extends the general idea beyond a box/rack with pooled accelerators and memory Edit: and IBM’s CAPI

splistud 6y ago
This plus NAND is where we're headed I believe

azornathogron 6y ago

It's not precisely what you're talking about, but you might be interested in Remote DMA: https://en.m.wikipedia.org/wiki/Remote_direct_memory_access https://en.m.wikipedia.org/wiki/Remote_direct_memory_access

t0mbstone 6y ago

The problem with putting RAM at the end of a cable is that RAM latency is highly dependent on distance from the CPU. Assuming RAM is 2 inches away from the cpu, and assuming the CPU is operating at 3 ghz, you are looking at 3 billion round trips per second over the distance of 2 inches, or a grand total of 12 billion inches of wire being crossed per second. Electric signals are limited by the speed of light, though. In a vacuum, light travels at 299,792,458 meters per second, or 11,802,852,677 (11 billion) inches per second. Do you see the bottleneck?

mechagodzilla 6y ago
That's not really how CPUs / RAM have worked since the 1980s. The CPU doesn't operate synchronously out of RAM, fetching data on each clock cycle. It operates from a hierarchical series of on-die caches, with only the L1 cache (typically a few 10s of kilobytes at most) operating close to how you describe. Logic on the CPU will send a series of commands to the RAM (along with data if it's a write), and there will be many commands 'in-flight' around the system at any given time, to hide the relatively high latencies involved (many 10s of nanoseconds). The actual propagation delay (around ~1 nanosecond/foot for cables) barely figures into it. Even the cables can have many 'bits' in flight at a time on them, and typically each 'direction' of the link forwards a clock along with the data (or it's embedded in the data stream) to avoid messy synchronization issues.
peter_d_sherman 6y ago
I do see the bottleneck! But, short of having a "how to subvert the speed of light" discussion, which would be exceedingly long (and probably unproductive!) -- you've given me an idea! Yes, you are correct that the speed of electrical propagation is limited, and does limit things! We're completely agreed there! OK, so here's my idea! F--- the electrical cable entirely! So, we have Quantum computers, Quantum bits, and all sorts of research on how to compute things with them, all kinds of professors and papers and companies and venture capital all researching how to do Quantum Computation... Well, I say F--- all of that! (In a polite, friendly, "yes your work is really genius and I acknowledge all of your brilliant contributions kind of way!"). Here's the grail! The grail of Quantum is NOT Quantum Computation -- but rather Quantum Communication! In other words, get rid of the damn electrical cable, and figure out a way to do that communication with a pair of connected-at-a-distance Quantum bits; that is -- Quantum Communication! In other words, Quantum Communication -- should replace wires and busses of all sorts, serial, parallel, electrical, light, what-have-you. That's the damn grail!... (pardon my language!) Not Quantum Computing!!! (brilliant though it is, I am not trying to knock it in any way, far from, quite the opposite!) Quantum Communication -- replacing wires and busses of all sorts, serial, parallel, electrical, light -- would be the Holy Grail -- of being able to build bigger computers (like imagine close-to-infinite RAM -- on one motherboard! Close-to-infinite RAM! Well, it would be off that motherboard... but Quantum Communication, if it were available, would, for all intensive purposes, make that RAM so connected, would have the net effect -- of physically existing on the motherboard, even though in actuality it would not be so!) So, to answer your question... YES, I DO SEE THE BOTTLENECK! But... equal-and-oppositely... Do you see my point?

simplyinfinity 6y ago

This is where Optane comes in. Faster than SSD, but larger than RAM: https://www.youtube.com/watch?v=cwy4ujt0qHM https://www.youtube.com/watch?v=cwy4ujt0qHM https://youtu.be/uHAfTty9UWY?t=263 https://youtu.be/uHAfTty9UWY?t=263

ksec 6y ago

> used as System RAM, just as slightly slower System RAM Intel Optane DIMM and Intel Optane SSD. Although Micron is selling their "Optane" Fab and Intel has yet to announce if they intend to buy it. >such links might include optical fiber Intel has been working on this for many years, Silicon Photonics and the goal is to have Compute, Memory and Storage in different "box" or even "Racks". >can be connected via high-speed serial links IBM OpenCAPI and OMI. Which allows up to 5PB of memory ( No more Big Data crap ) , and if I remember correctly with additional 10ns latency.

dharmab 6y ago
> Although Micron is selling their "Optane" Fab and Intel has yet to announce if they intend to buy it. I have several close friends working at that fab and I am astounded that Micron is both still in business and hasn't caused a chemical disaster in Lehi yet. It's a fantastically mismanaged and unsafe workplace.