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> 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 e
by 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 agoI 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 agoFor 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 agoMore 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 agoI'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 agoThe 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 agoJudging by that LPDDR5X was announced in 2019; and LPDDR6X was just announced in 2024... we're still a full laptop/desktop cycle away.