I have a system with an AMD 486DX4/100 and 256K of direct-mapped
write-back cache and 12 megs of 70 ns ram. This system has an
AMI BIOS Dated 07/25/94 and a SIS chipset. I can easily expand
this motherboard to either 16 megs or 28 megs by adding one 72
pin single sided SIMM.
I have read that if systems with direct mapped caches are
expanded to more than 16 megs of ram they get much slower
because every time the processor changes which 16 meg it
addresses the cache becomes invalid. Is this true?
Is there any way I can prevent this other than disabling the
external cache entirely or replacing the motherboard? Would
increasing the total amount of cache ram to 512K or one meg help?
This BIOS allows the user to set two areas of memory as non-
cacheable but they seem to be limited to four megs each. Would
it help to make eight of the 28 megs non-cacheable?
With my motherboard, would it be better for me to upgrade to 16
megs or 28 megs for running OS/2 or Windows 95? Thank you in
advance for all replies.
If there is another newsgroup that would be more appropriate for this
question, please let me know.
If it is not too much trouble, please send e-mail as well as
answering in the newsgroup. My news feed is not always that
reliable (I see replies to messages I never see every day) and I
am sometimes too ill to check my newsgroups for several days.
Thank you in advance for all replies.