lane@dalcs.UUCP (John Wright/Dr. Pat Lane) (10/03/88)
I have a few questions about adding RAM to a PC or XT type system:
1. What memory speeds are appropriate for different CPU speeds? What other
factors are involved? Can memory chips with different ratings be mixed?
2. What about 64Kbit chips vs. 256Kbit or whatever? Certain memory boards
I've seen seem to allow different types to be used but it isn't clear
whether they can be used at the same time on a board, what restrictions
there might be on this, or how the board would figure out what was going
on.
3. Could you have 0K on the motherboard and all of the system's RAM on an
expansion board, assuming the expansion board allowed you to the start
it's memory addressing at 0? The system-board switchs on the XT would
appear to have an undefined setting that would logically (to me) be 0K
but not on the PC-1 or PC-2.
Also, on a Compaq 286 with a 2 Meg RAM board presently populated with 1 Meg
of RAM in 4 banks of 9 chips (from which I deduce 256Kbit chips). The chips
are marked:
Hitachi
Jana s-10? (this line I probably have wrong)
8740 299C
HM51258P-100
I have found catalog listings for a DRAM chip HM51258-100 which was indicated
to be a 100 nanosecond CMOS chip. I desire to add the other 1 Meg of RAM:
4. Is my existing memory 256Kbit, 100 nsec, CMOS chips? Would any DRAM chip
for a PC meeting these criteria work? What about the descrepency of "P"
in the name (it was suggested that this refers to the case being plastic
rather than ceramic or whatever)? Do any of the other numbers and markings
on the chip have any significance?
Would be most grateful for any enlightenment on this. Thank you.
--
John Wright ///////////////// Phone: 902-424-3805 or 902-424-6527
Post: c/o Dr Pat Lane, Biology Dept, Dalhousie U, Halifax N.S., CANADA B3H-4H8
Cdn/Bitnet: lane@cs.dal.cdn Arpa: lane%dalcs.uucp@uunet.uu.net
Uucp: lane@dalcs.uucp or {uunet,watmath,utai,garfield}!dalcs!lane pshen@mit-atrp.UUCP (Paul Shen) (10/05/88)
In article <3012@dalcs.UUCP> lane@dalcs.UUCP (John Wright/Dr. Pat Lane) writes: >I have a few questions about adding RAM to a PC or XT type system: > >1. What memory speeds are appropriate for different CPU speeds? What other > factors are involved? Can memory chips with different ratings be mixed? > For 10MHz system, 100ns is required. For 12MHz system, 80ns is required. As the thumb of the rule, memory speed has to satisfy memory speed < 1 / system colck If you mix the different ratings, it will work as long as all the chips satisfy the above requirement. >2. What about 64Kbit chips vs. 256Kbit or whatever? Certain memory boards > I've seen seem to allow different types to be used but it isn't clear > whether they can be used at the same time on a board, what restrictions > there might be on this, or how the board would figure out what was going > on. There is dip switches to set for the appropriate type of ram chip. Paul Shen pshen@atrp.media.mit.edu