3 ms·
> Doesn't the CPU need equal length parallel lines to the memory? Yes, but you could do that within the tower. Maintaining signal integrity through the connect
by mbell 13y ago
> Doesn't the CPU need equal length parallel lines to the memory?
Yes, but you could do that within the tower. Maintaining signal integrity through the connectors and/or propagation delay due to trace length would be the limiters.
> Or is there a serial interface to memory nowadays?
Not for PC level memory speeds.
> Wow.. so in the video they plugin a CPU module.
All the pictures show "CPU / RAM" in the same module, which makes a lot more sense to me as an EE.
- vonmoltke 13y ago> Yes, but you could do that within the tower. Maintaining signal integrity through the connectors and/or propagation delay due to trace length would be the limiters. They can, and probably will, also use signal path equalizers.
- mbell 13y agoThat would be problematic at best given the clock speed and timing requirements of DDR3.
- vonmoltke 13y agoMaxim claims to have the technology for gigabit signal path equalizers: http://pdfserv.maximintegrated.com/en/an/AN996.pdf http://pdfserv.maximintegrated.com/en/an/AN996.pdf
- mbell 13y agoI'm not seeing much connection between the IC being talked about in that App note and what would be needed to support DDR3.
- al2o3cr 13y agoThose are for a single serial signal - as the note indicates, mostly to replace very-short-run fiber optics. The challenges with routing DDR4 signals through connectors, etc are mostly about skew: if any signals are delayed by anything approaching 1/2 a clock period (~1cm on FR4 board) relative to each other, everything is fucked. In addition, some digging on the MAX3800 referenced there indicates that it has a power consumption of 200 mW, and a "budgetary" price of $6.90 each. Since a typical DDR interface is 100+ signals, you're looking at spending 20+ W and the price of a midrange PC just on signal integrity, and that's assuming those chips even do what you want. There are systems that work like Christine - but they are things like IBM mainframes that don't suffer from cost constraints.
- dippyskoodlez 13y agoGigabit? http://en.wikipedia.org/wiki/DDR3_SDRAM#JEDEC_standard_modules http://en.wikipedia.org/wiki/DDR3_SDRAM#JEDEC_standard_modul... Try 17GB with little latency tolerance.