5 ms·

I really want LPDDR5X (and future better versions) to become standard on desktops, alongside faster and more-numerous memory controllers to increase overall ban

I really want LPDDR5X (and future better versions) to become standard on desktops, alongside faster and more-numerous memory controllers to increase overall bandwidth. Why hasn't CAMM gotten anywhere? I also really want an update to typical form factors and interconnects of desktop computers. They've been roughly frozen for decades. Off the top of my head: - Move to single-voltage power supplies at 36-57 volts. - Move to bladed power connectors with fewer pins. - Get rid of the "expansion card" and switch to twinax ribbon interconnects. - Standardize on a couple sizes of "expansion socket" instead, putting the high heat-flux components on the bottom side of the board. - Redesign cases to be effectively a single ginormous heatsink with mounting sockets to accept things which produce heat. - Kill SATA. It's over. - Use USB-C connectors for both power and data for internal peripherals like disks. Now there's no difference between internal and external peripherals.

gjsman-1000 2y ago
> Why hasn't CAMM gotten anywhere? Framework asked AMD if they could use CAMM for their new Framework Desktop. AMD actually humored the request and did some engineering, with simulations. According to Framework, the memory bandwidth on the simulations was less than half of the soldered version. This completely defied the entire point of the chip - the massive 256 bit bus ideal for AI or other GPU-heavy tasks, which allows this chip to offer the features it does. This is also why Framework has apologized for non upgradability, but said it can’t be helped, so enjoy fair and reasonable RAM prices. Previously, it had been speculated that CAMM had a performance penalty, but Framework’s engineer on video saying it was that bad was fairly shocking.
- arghwhat 2y ago
  I do not believe they were asking for CAMM as replacement for soldered RAM, but as an upgrade for DIMMs in desktop. CAMM is touted as being better than DIMMs when it comes to signal integrity and possible speed. Soldered of course beat any socket, in-package beats any soldered RAM, and on-die beat any external component. That AMD Strix Halo is unable to maintain signal integrity for any socketed RAM is a Strix Halo problem, not a socket problem. They probably backed themselves a bit into a corner with other parts of the design sacrifying tolerances on the memory side, and it's a lot easier to push motherboard design requirements than redoing a chip. If this wasn't a Strix Halo issue, then they would have been able to run with socketed memory with a lower memory clock. All CPUs, this one included, has variable memory clocks that could be utilized and perform memory training as even the PCB traces to the chip cause significant signal degradation.
  - kimixa 2y ago
    For signal integrity issues increasing the link power can often overcome some of the issues caused by longer traces and connectors in the line - while less of an issue for desktop devices, then that goes against the ideal of a low-powered device with limited cooling. Doubly so as it's hard to re-clock in the timescales needed for intermittent use power saving, so will be using that extra power when idle. I suspect the earlier comment about "Half the performance with CAMM" is likely at iso-power, but that might still be a pretty big dealbreaker.
    - arghwhat 2y ago
      More power is to overcome switching losses and parasitic reactances. You can increase drive strength up to a limit to overcome this, but a slight clock reduction will make things work at the same power. CPU's and GPU's reclock extremely fast to my knowledge, but what we're talking about isn't dynamic reclocking, just limiting the max clock as suitable to the system design. We already see this when we have laptop silicon that run faster clocks when using soldered RAM compared to when the same silicon is using socketed counterparts. That this wasn't an option probably mean that they're either far too close to the limit, or unwilling to allow a design that runs below max speed.
- sunshowers 2y ago
  I'm curious how much the CUDIMM thing Intel is doing, where the RAM has its own clock, can help in the CAMM context. The Zen 4/5 memory controller doesn't support it but a future one might.
- Tuna-Fish 2y ago
  The problem was specifically routing the 256-bit LPDDR5X out of the chip into the CAMM2 connector. This is hard to do with such a wide bus, because LPDDR5X wasn't originally designed for it. LPDDR6X is designed for it, and an use CAMM2.
  - gjsman-1000 2y ago
    Judging by that LPDDR5X was announced in 2019; and LPDDR6X was just announced in 2024... we're still a full laptop/desktop cycle away.
simoncion 2y ago
> - Move to single-voltage power supplies at 36-57 volts. Why? And why not 12V? Please be specific in your answers. > - Get rid of the "expansion card" and switch to twinax ribbon interconnects. If you want that, it's available right now. Look for a product known as "PCI Express Riser Cable". Given that the "row of slots to slot in stiff cards" makes for nicely-standardized cases and card installation procedures that are fairly easy to understand, I'm sceptical that ditching slots and moving to riser cables for everything would be a benefit. > - Kill SATA. It's over. I disagree, but whatever. If you just want to reduce the number of ports on the board, mandate Mini SAS HD ports that are wired into a U.2 controller that can break each port out into four (or more) SATA connectors. This will give folks who want it very fast storage, but also allow the option to attach SATA storage. > - Use USB-C connectors for both power and data for internal peripherals like disks. God no. USB-C connectors are fragile as all hell and easy to mishandle. I hate those stupid little almost-a-wafer blades. > - Standardize on a couple sizes of "expansion socket" instead... What do you mean? I'm having trouble envisioning how any "expansion socket" would work well with today's highly-variably-sized expansion cards. (I'm thinking especially of graphics accelerator cards of today and the recent past, which come in a very large array of sizes.) > - Redesign cases to be effectively a single ginormous heatsink with mounting sockets... See my questions to the previous quote above. I currently don't see how this would work.
- deleted 2y ago
  [deleted]
- arghwhat 2y ago
  > Why? And why not 12V? Please be specific in your answers. Higher voltages improve transmission efficiency, in particularly for connectors, as long as sufficient insulation is easy to maintain. Datacenters are looking at 48V for a reason. Nothing comes for free though, and it makes for slightly more work for the various buck converters. > God no. USB-C connectors are fragile as all hell and easy to mishandle. I hate those stupid little almost-a-wafer blades. They are numerous orders of magnitude more rugged than any internal connector you've used - most of them are only designed to handle insertion a handful of times (sometime connectors even only work once!), vs. ten thousand times for the USB-C connector. In that sense, a locking USB-C connector would be quite superior. ... on that single metric. It would be ridiculously overcomplicated, driving up part costs when a trivial and stupidly cheap connector can do the job sufficiently. Having to run off 48V to push 240W and have no further power budget at all also increase complexity, cost and add limitations. USB-C is meant for end-user things where everything has to be crammed into the same, tiny connector, where it does great.
wmf 2y ago
There's a rumor that future desktops will use LPDDR6 (with CAMMs presumably) instead of DDR6. Of course CAMMs will be slower so they might "only" run at ~8000 GT/s while soldered LPDDR6 will run at >10000.
- Tuna-Fish 2y ago
  LPDDR6 won't go that low, even on CAMM2. The interface is designed for up to 14.4Gbps, with initial modules aiming for 10.6Gbps.
- nsteel 2y ago
  What's the advantage of LPDDR6 Vs DDR6 given the latter will be faster ?

gjsman-1000 2y ago

> Why hasn't CAMM gotten anywhere? Framework asked AMD if they could use CAMM for their new Framework Desktop. AMD actually humored the request and did some engineering, with simulations. According to Framework, the memory bandwidth on the simulations was less than half of the soldered version. This completely defied the entire point of the chip - the massive 256 bit bus ideal for AI or other GPU-heavy tasks, which allows this chip to offer the features it does. This is also why Framework has apologized for non upgradability, but said it can’t be helped, so enjoy fair and reasonable RAM prices. Previously, it had been speculated that CAMM had a performance penalty, but Framework’s engineer on video saying it was that bad was fairly shocking.

arghwhat 2y ago
I do not believe they were asking for CAMM as replacement for soldered RAM, but as an upgrade for DIMMs in desktop. CAMM is touted as being better than DIMMs when it comes to signal integrity and possible speed. Soldered of course beat any socket, in-package beats any soldered RAM, and on-die beat any external component. That AMD Strix Halo is unable to maintain signal integrity for any socketed RAM is a Strix Halo problem, not a socket problem. They probably backed themselves a bit into a corner with other parts of the design sacrifying tolerances on the memory side, and it's a lot easier to push motherboard design requirements than redoing a chip. If this wasn't a Strix Halo issue, then they would have been able to run with socketed memory with a lower memory clock. All CPUs, this one included, has variable memory clocks that could be utilized and perform memory training as even the PCB traces to the chip cause significant signal degradation.
- kimixa 2y ago
  For signal integrity issues increasing the link power can often overcome some of the issues caused by longer traces and connectors in the line - while less of an issue for desktop devices, then that goes against the ideal of a low-powered device with limited cooling. Doubly so as it's hard to re-clock in the timescales needed for intermittent use power saving, so will be using that extra power when idle. I suspect the earlier comment about "Half the performance with CAMM" is likely at iso-power, but that might still be a pretty big dealbreaker.
  - arghwhat 2y ago
    More power is to overcome switching losses and parasitic reactances. You can increase drive strength up to a limit to overcome this, but a slight clock reduction will make things work at the same power. CPU's and GPU's reclock extremely fast to my knowledge, but what we're talking about isn't dynamic reclocking, just limiting the max clock as suitable to the system design. We already see this when we have laptop silicon that run faster clocks when using soldered RAM compared to when the same silicon is using socketed counterparts. That this wasn't an option probably mean that they're either far too close to the limit, or unwilling to allow a design that runs below max speed.
sunshowers 2y ago
I'm curious how much the CUDIMM thing Intel is doing, where the RAM has its own clock, can help in the CAMM context. The Zen 4/5 memory controller doesn't support it but a future one might.
Tuna-Fish 2y ago
The problem was specifically routing the 256-bit LPDDR5X out of the chip into the CAMM2 connector. This is hard to do with such a wide bus, because LPDDR5X wasn't originally designed for it. LPDDR6X is designed for it, and an use CAMM2.
- gjsman-1000 2y ago
  Judging by that LPDDR5X was announced in 2019; and LPDDR6X was just announced in 2024... we're still a full laptop/desktop cycle away.

simoncion 2y ago

> - Move to single-voltage power supplies at 36-57 volts. Why? And why not 12V? Please be specific in your answers. > - Get rid of the "expansion card" and switch to twinax ribbon interconnects. If you want that, it's available right now. Look for a product known as "PCI Express Riser Cable". Given that the "row of slots to slot in stiff cards" makes for nicely-standardized cases and card installation procedures that are fairly easy to understand, I'm sceptical that ditching slots and moving to riser cables for everything would be a benefit. > - Kill SATA. It's over. I disagree, but whatever. If you just want to reduce the number of ports on the board, mandate Mini SAS HD ports that are wired into a U.2 controller that can break each port out into four (or more) SATA connectors. This will give folks who want it very fast storage, but also allow the option to attach SATA storage. > - Use USB-C connectors for both power and data for internal peripherals like disks. God no. USB-C connectors are fragile as all hell and easy to mishandle. I hate those stupid little almost-a-wafer blades. > - Standardize on a couple sizes of "expansion socket" instead... What do you mean? I'm having trouble envisioning how any "expansion socket" would work well with today's highly-variably-sized expansion cards. (I'm thinking especially of graphics accelerator cards of today and the recent past, which come in a very large array of sizes.) > - Redesign cases to be effectively a single ginormous heatsink with mounting sockets... See my questions to the previous quote above. I currently don't see how this would work.

deleted 2y ago
[deleted]
arghwhat 2y ago
> Why? And why not 12V? Please be specific in your answers. Higher voltages improve transmission efficiency, in particularly for connectors, as long as sufficient insulation is easy to maintain. Datacenters are looking at 48V for a reason. Nothing comes for free though, and it makes for slightly more work for the various buck converters. > God no. USB-C connectors are fragile as all hell and easy to mishandle. I hate those stupid little almost-a-wafer blades. They are numerous orders of magnitude more rugged than any internal connector you've used - most of them are only designed to handle insertion a handful of times (sometime connectors even only work once!), vs. ten thousand times for the USB-C connector. In that sense, a locking USB-C connector would be quite superior. ... on that single metric. It would be ridiculously overcomplicated, driving up part costs when a trivial and stupidly cheap connector can do the job sufficiently. Having to run off 48V to push 240W and have no further power budget at all also increase complexity, cost and add limitations. USB-C is meant for end-user things where everything has to be crammed into the same, tiny connector, where it does great.

wmf 2y ago

There's a rumor that future desktops will use LPDDR6 (with CAMMs presumably) instead of DDR6. Of course CAMMs will be slower so they might "only" run at ~8000 GT/s while soldered LPDDR6 will run at >10000.

Tuna-Fish 2y ago
LPDDR6 won't go that low, even on CAMM2. The interface is designed for up to 14.4Gbps, with initial modules aiming for 10.6Gbps.
nsteel 2y ago
What's the advantage of LPDDR6 Vs DDR6 given the latter will be faster ?