Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!sun-barr!lll-winken!ames!vsi1!altos!altos86!rcollins From: rcollins@altos86.Altos.COM (Robert Collins) Newsgroups: comp.sys.ibm.pc.hardware Subject: Re: Mixing 1M and 256K simms- Why not? Keywords: Reasons for disallowing? Message-ID: <11@altos86.Altos.COM> Date: 26 Feb 91 17:18:57 GMT References: <1991Feb23.045704.985@cbnewsd.att.com> Reply-To: rcollins@altos86.UUCP (Robert Collins) Organization: Altos Computer Systems, San Jose, CA Lines: 48 In article <1991Feb23.045704.985@cbnewsd.att.com> bash@cbnewsd.att.com (thomas.w.basham) writes: > >There seems to be a consensus (or myth) that a system using SIMM >memory can't mix 1M and 256K simms. My machine uses two banks of > >Seems to me it's nothing but poor BIOS programming that can't access >the separate banks with different ranges. I've mixed ram types in As a BIOS programmer who has ported to a few chipsets, I think it is safe to say that it depends on the capabilities of the chipset. I can't think of a single BIOS implementation doesn't take full advantage of the chips used in the system. Consider the C&T NEAT chipset. The following is a list of valid configurations in the NEAT (& LEAP): BANK0 BANK1 BANK2 BANK3 Total 1 0k 0k 0k 0k 0k 2 256k 0k 0k 0k 512k 3 1M 0k 0k 0k 2M 4 256k 64k 0k 0k 640k 5 256k 256k 0k 0k 1M (+) 6 1M 1M 0k 0k 4M (+) 7 256k 256k 256k 0k 1.5M 8 256k 256k 1M 0k 3M 9 1M 1M 1M 0k 6M 10 256k 64k 256k 256k 1.64M 11 256k 256k 256k 256k 2M (*) 12 256k 64k 1M 1M 6.64M 13 256k 256k 1M 1M 5M (+) 14 1M 1M 1M 1M 8M (*) (+) = 2-way page interleave mode (*) = 4-way page interleave mode The above description is EVERY possible configuration this chipset allows. As you can see, not every permutation of 256k, 64k, and 1M chips is programmable into this chipset. So to answer your question: it is not sloppy BIOS programming that inhibits the mixture, it's most likely the chipset. -- "Worship the Lord your God, and serve him only." Mat. 4:10 Robert Collins UUCP: ...!sun!altos86!rcollins HOME: (408) 225-8002 WORK: (408) 432-6200 x4356