yarvin-norman@CS.YALE.EDU (Norman Yarvin) (06/14/90)
In article <1990Jun13.051957.17219@portia.Stanford.EDU> dhinds@portia.Stanford.EDU (David Hinds) writes: > It isn't clear to me why DRAM's are nearly always bit-wide or nibble- >wide, besides tradition. A couple of reasons come to mind: To make external address decode easier. Building an 8-bit-wide 256K byte memory module with 256K x 1 chips requires no external address decode; all the chips can be enabled whenever you're accessing memory. Building it with 32K x 8 chips requires you to have a decoder feeding the enable lines -- an extra chip and reduced speed. To reduce pin count. A 256K x 1 chip needs 18 address bits and one data bit; a 32Kx8 chip needs 15 address bits and 8 data bits. That's 4 more bits that have to go into/out of the chip for each access. -- Norman Yarvin yarvin-norman@cs.yale.edu "Obviously crime pays, or there'd be no crime." -- G. Gordon Liddy