toma@swsrv1.cirr.com (Tom Armistead) (04/15/91)
Could someone tell me how to figure what the speed of RAM needs to be for
different speed of PC's. For instance, how fast does the RAM need to be
for a 33mhz 386? 80 or 70 nanoseconds? How about for a 33mhz 486?
Thanks,
Tom
--
Tom Armistead - Software Services - 2918 Dukeswood Dr. - Garland, Tx 75040
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toma@swsrv1.cirr.com {egsner,ozdaltx,void}!swsrv1!tomaphil@brahms.amd.com (Phil Ngai) (04/16/91)
toma@swsrv1.cirr.com (Tom Armistead) writes: >Could someone tell me how to figure what the speed of RAM needs to be for >different speed of PC's. It's very simple. Get the manual for the motherboard and read it. "Could someone tell me how to figure out what size tires you need for different model of cars?" -- The best way to preserve your RKBA is to vote Libertarian.
dorsai@iear.arts.rpi.edu (gregory d moncreaff) (04/16/91)
In article <1991Apr15.233221.18417@amd.com> phil@brahms.amd.com (Phil Ngai) writes: >toma@swsrv1.cirr.com (Tom Armistead) writes: > >>Could someone tell me how to figure what the speed of RAM needs to be for >>different speed of PC's. > >It's very simple. Get the manual for the motherboard and read it. > >"Could someone tell me how to figure out what size tires you need for >different model of cars?" lighten UP! please. all the guy seemed to want to know was what the general relation between processor chip clock speed (MHz) and the access time (ns) required for the rams. while it is all very well to sit there and say RTFM over and over, you do little to fufill the needs of many of the usenet community. Mr Armistead may well have a motherboard manual or two at his disposal but that would prove insufficient for answering a question of the bredth which he set forth. Mr Artmistead would require motherboard manuals for xt's at's 386sx 386's and 486's as for the requested information, i believe that anything running under 12MHz should be able to use 100ns rams. i have seen 80ns rams used from 16Mhz 386sx and 20MHz 286 upto 25MHz. this is from practical, life experience. getting theoretical, on the other hand, my memory controller, in a 386sx-16Mhz board, the 82c212, says that it will support 0 wait states with 120ns ram. as the motherboard was sent to me with 80ns rams on it i am slightly confused. perhaps Mr Ngai can enligten us? -- "A perfect democracy, a 'warm body' democracy in which every adult may vote and all votes count equally, has no internal feedback for self-correction. It de- pends solely on the wisdom and self restraint of citizens ... which is opposed by the folly and lack of self-restraint of other citizens. What is supposed to
phil@brahms.amd.com (Phil Ngai) (04/16/91)
dorsai@iear.arts.rpi.edu (gregory d moncreaff) writes: >please. all the guy seemed to want to know was what the general relation >between processor chip clock speed (MHz) and the access time (ns) required Unfortunately, there is no general relationship. It depends on: the processor (286 is different from 386 is different from 486) the motherboard (some motherboards automatically put in a wait state), whether there is cache whether the memory is interleaved whether it is paged the chipset how the chipset is configured how much memory you have how big your memory chips are what kind of memory chips you have (1megx1 or 256Kx4) And a whole bunch of other things. Just because you want a simple answer doesn't mean there is one. >getting theoretical, on the other hand, my memory controller, in a 386sx-16Mhz >board, the 82c212, says that it will support 0 wait states with 120ns ram. as >the motherboard was sent to me with 80ns rams on it i am slightly confused. >perhaps Mr Ngai can enligten us? You prove my point. -- The best way to preserve your RKBA is to vote Libertarian.
velasco@beowulf.ucsd.edu (Gabriel Velasco) (04/20/91)
dorsai@iear.arts.rpi.edu (gregory d moncreaff) writes: >... on the other hand, my memory controller, in a 386sx-16Mhz >board, the 82c212, says that it will support 0 wait states with 120ns ram. as >the motherboard was sent to me with 80ns rams on it i am slightly confused. The 120ns and 80ns times refer to how long it takes for the memory chip to return the data that have been requested. Clearly, an 80ns chip is faster than a 120ns chip because it takes less time to access it. A wait state is exactly that. The CPU has to wait because the memory takes too long to return the data that the CPU has requested. A very fast CPU coupled with slow memory may have to wait many cycles before it gets it data. During this time, it does nothing. Memory access time can place a lower bound on system performance. Since your CPU will support 0 wait states (i.e., it doesn't have to wait) with a 120ns ram, it seems logical that it would support 0 wait states with faster 80ns ram. Even though 80ns chips are usually more expensive than 120ns chips, manufacturers often run out of the more common, less expensive chips and have to substitute the more expensive chips that they have lying around rather than stop production. -- ________________________________________________ <>___, / / | ... and he called out and said, "Gabriel, give | /___/ __ / _ __ ' _ / | this man an understanding of the vision." | /\__/\(_/\/__)\/ (_/_(/_/|_ |_______________________________________Dan_8:16_|