Path: utzoo!attcan!uunet!mcsun!corton!chorus!opera!mir From: mir@opera.chorus.fr (Adam Mirowski) Newsgroups: comp.sys.ibm.pc.hardware Subject: Re: Memory speeds Message-ID: <7813@chorus.fr> Date: 11 Feb 91 14:11:38 GMT References: Sender: mir@chorus.fr Reply-To: mir@opera.chorus.fr (Adam Mirowski) Organization: Chorus systemes, Saint Quentin en Yvelines, France Lines: 38 In article , vcl@mimas.UUCP (Victor C. Limary) writes: %% %% I have a 16MHz 386 computer with 2 megs of mixed 80ns and 100ns SIMMS. %% I am thinking of buying 4 1meg x 9 SIMMS, but I'm not sure about what %% speed memory I should get. Most likely, I will be getting at least 80ns, %% but lately, I've seen lots of 70ns and 60ns RAM. Is there a big %% difference in speed with each 10ns? Prices are about $5-$15 more for %% every 10ns speed increase with the memory. Is getting 70ns or even 60ns %% SIMMs worth the extra money with a 16MHz computer? %% Thanks in advance. RAM chips cannot tell the motherboard that they are faster or slower. Also, the motherboard can't by itself tell the speed of the installed chips... It must be told, either by configuration switches, or by the setup data stored in backed CMOS memory. If you don't tell your motherboard that the new SIMMs are faster than the old ones, it won't tighten the timings and speed the operation. So if your motherboard isn't configurable for faster chips, all you need is 100ns SIMMs (as you already have some and that works). On a 20Mhz 386 I have seen two switches (for reading and writing) that enabled 100ns, 80 and 70ns operation. On my 33Mhz, the built-in setup program lets me choose between 0 and 3 wait states for reading and 0-1 wait states for writing. The board manual shows the correct settings depending on the chip speed. I should warn you that if you change your 8 256K chips (I suppose) against 4 of 1M capacity, you will loose the memory interleaving possibility (if you have a DX) until you have 8 chips (2 banks) again. That will certainly drop your processing speed. Of course, if your 386 is a SX, the bus is only 16 bits wide so even with 4 chips, or 32 bits of memory access, interleave is possible. -- Adam Mirowski, mir@chorus.fr (FRANCE), tel. +33 (1) 30-64-82-00 or 74 Chorus systemes, 6, av.Gustave Eiffel, 78182 Saint-Quentin-en-Yvelines CEDEX