watt@eleazar.dartmouth.edu (Gill Watt) (03/01/91)
howdy, I have a curiosity question: Why do the mac laptops use SRAMS instead of the standard DRAMS? Is it because DRAM refresh circuitry consumes a lot more power? If so, how much more? Anyone know any other reasons? Thanks. -- --------------------------------------------------------------------- Gill Watt (watt@eleazar.dartmouth.edu) Thayer School of Engineering, Dartmouth College, Hanover, NH 03755 ---------------------------------------------------------------------
henry@zoo.toronto.edu (Henry Spencer) (03/02/91)
In article <1991Mar1.020935.7107@dartvax.dartmouth.edu> watt@eleazar.dartmouth.edu (Gill Watt) writes: >Why do the mac laptops use SRAMS instead of the standard DRAMS? >Is it because DRAM refresh circuitry consumes a lot more >power? If so, how much more? It's not the refresh circuitry so much as the DRAMs themselves. DRAMs simply are not low-power technology. The right sort of SRAMs are. There is no single meaningful answer to "how much more". It can be orders of magnitude, if you really work at making the SRAM system economical. In particular, where DRAMs draw milliamps, SRAMs in low-voltage standby typically draw nanoamps. -- "But this *is* the simplified version | Henry Spencer @ U of Toronto Zoology for the general public." -S. Harris | henry@zoo.toronto.edu utzoo!henry
rashid@magnus.ircc.ohio-state.edu (Robert G Rashid) (03/03/91)
In article <1991Mar1.020935.7107@dartvax.dartmouth.edu> watt@eleazar.dartmouth.edu (Gill Watt) writes: > >howdy, > >I have a curiosity question: > >Why do the mac laptops use SRAMS instead of the standard >DRAMS? > >Is it because DRAM refresh circuitry consumes a lot more >power? If so, how much more? > >Anyone know any other reasons? > >Thanks. > > >-- >--------------------------------------------------------------------- >Gill Watt (watt@eleazar.dartmouth.edu) >Thayer School of Engineering, Dartmouth College, Hanover, NH 03755 >--------------------------------------------------------------------- There is a company that makes a memory board for the portable which uses drams as the memory chip. The board takes care of memory refresh, as I understand, and the total power consumption is less than the equivalent sram or static ram chip. The drawback is in sleep mode, where the chips require power to maintain memory. This is not the case with sram and static ram chips. I just got the board from Computer Care, and am happy with it. They have 4M chips on the board, but it was cheaper than 4M (or 3M) of static ram,etc. Since I am usually near power a few times a day, I can charge if nec. and still use without power for a few hours. I notice that there is more power used now that I have 4M than when I had 1M (no suprise). Disclaimer: I have no connections with Computer Care, except as a satisfied customer. -- | Bob Rashid | Rashid.1@osu.edu | | College of Dentistry | 305 W. 12th Ave. | | The Ohio State University | Columbus, OH 43210 |