Hi John Walliker; That Micron data sheet is just the
short form. If you want links to full data sheets, I've
thrown some into this post. (But they are big!)
You supposed that rambus interface will have a lower power
consumption than the DDR one. This may be true, but the
vast majority of the power consumption in a DRAM based
memory system is in the memory chips, and rambus chips are
power hogs.
Samsung has a full data sheet on DDR, so we can compare
power consumption between RDRAM, DDR and SDRAM...
Comparing power consumption of 64Mb, x16 size parts from
Samsung:
Oper. P.Dn P.Up Brst Refr
ICC1 ICC2P ICC2N ICC4 ICC5
SDRAM: 110 1 20 145 150 mA (max)
DDR: 125 20 45 TBD 200 mA (max)
IDD,STBY IDD,ATTN IDD,ATTN-W IDD,ATTN-R
Rambus (a): 120 200 700 575(b) mA (max)
notes
a. The CMOS interface consumes power in all power states.
b. This does not include the IOL sink current. The RDRAM
dissipates IOLxVOL in each output driver when a logic
one is driven.
From the above, it is quite obvious that given two memory
systems of the same size, the rambus memory system is going
to use about twice as much power. If you doubt this, why
don't you go find the articles published in EE-Times
announcing new heat sinks devoted to rambus chips? You
won't see any such parts announced for DDR SDRAMs, and the
reason is that they are a lot more energy efficient.
As I, and many (non INTC or RMBS) industry experts have
said before, rambus is a technology that is optimal for
very small memory systems, such as the ones used in
playstations. To use this technology for large memories
isn't real bright, because of power consumption, chip cost,
ease of design, and ease of manufacture.
-- Carl |
