Path: utzoo!utgpu!news-server.csri.toronto.edu!bonnie.concordia.ca!uunet!zaphod.mps.ohio-state.edu!think.com!snorkelwacker.mit.edu!bloom-picayune.mit.edu!athena.mit.edu!pshuang From: pshuang@athena.mit.edu (Ping-Shun Huang) Newsgroups: comp.sys.ibm.pc.hardware Subject: Re: What is the difference between SIMMs and DRAMs? Message-ID: Date: 30 Jun 91 04:15:44 GMT References: <3155@amsaa-cleo.brl.mil> Sender: news@athena.mit.edu (News system) Organization: Massachusetts Institute of Technology Lines: 33 In-Reply-To: cgaeth@amsaa-cleo.brl.mil's message of 28 Jun 91 15:10:52 GMT In article <3155@amsaa-cleo.brl.mil> cgaeth@amsaa-cleo.brl.mil (Christopher Gaeth) writes: > I would like to know the difference between SIMM chips and DRAM > chips. I'm planning on adding more memory to my machine and it takes SIMMS > and I was wondering why they are so much more expensive (10X's as much). SIMM's cost much more than DRAM chips in terms of dollars per unit, but that's because SIMM's provide more RAM per unit. A SIMM (Single Inline Memory Module) bank contains either eight or nine (depending on whether your machine wants parity) DRAM chips. Something which is rather confusing is the abbreviation "b". For DRAM chips, the abbreviation stands for bits, but for SIMM's the abbreviation stands for bytes. A machine with eight 1Mb SIMM's has eight times the memory of a machine with eight 1Mb DRAM chips. Commonly seen labels for RAM expansion parts: ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 1Mbx9 SIMM provides one megabytes of memory 1Mbx8 SIMM one megabyte 256Kbx9 SIMM two hundred fifty-six kilobytes 256Kbx8 SIMM two hundred fifty-six kilobytes 1Mb DRAM one megabit = one hundred twenty-eight kilobytes 256Kb DRAM two hundred fifty-six kilobits = thirty-two kilobytes [Additional numbers which are multiples of ten running from about 60 to 120 are likely to indicate the access speed in nanoseconds.] Hope that helps clear up any confusion. -- Above text where applicable is (c) Copyleft 1991, all rights deserved by: UNIX:/etc/ping instantiated (Ping Huang) [INTERNET: pshuang@athena.mit.edu]