munish@ms.uky.edu (Munish Mehra) (09/20/89)
I am putting together a 386 which will be used for graphics along with other things. My question is that does the cache make a significant difference and if so how much ? I have heard opposing views. i.e. the cache doesn't really make any difference and that it makes a big difference. Since 386 motherboards with cache are about $300 to $400 more expensive, I think it is better to use that towards a start on a good graphics coprocessor. Any views will be appreciated. Thanks
davidsen@crdos1.crd.ge.COM (Wm E Davidsen Jr) (09/21/89)
In article <12718@s.ms.uky.edu>, munish@ms.uky.edu (Munish Mehra) writes: | I am putting together a 386 which will be used for graphics along | with other things. | | My question is that does the cache make a significant difference | and if so how much ? It depends on the speed of the memory you use with the system. If you have 60ns interleaved column static you will not save much. If you have slow memory you will save a lot. Two reference points: System A: AMI MB, 32 bit 0w/s on MB, 16 bit 1w/s memory on AT bus. Without cache the 16 bit memory is 35-40% slower. With cache enabled 10-15% slower. System B: AMI 25 MHz with 4MB 60ns, 32 bit 0w/s on board. Turning on cache saves about 5%. If you will be running fast interleaved memory the cache will be of less use than if you have to save a few bucks and go with slower memory. You can pay for the cache, or pay for the memory and fancy circuitry. Another consideration is that if you run DOS and use extra memory for RAM, EMS, etc, you are not *executing* in the memory above 1MB, so a system which has a fast 1MB on the MB may be fine without cache. If you run UNIX or OS/2 you take a much larger performance hit. Sorry there's no one yes or no answer. -- bill davidsen (davidsen@crdos1.crd.GE.COM -or- uunet!crdgw1!crdos1!davidsen) "The world is filled with fools. They blindly follow their so-called 'reason' in the face of the church and common sense. Any fool can see that the world is flat!" - anon