What are “single-sided” and par “double-sided” 72-pin SIMMs?
\par \par All 72-pin SIMMs are 32 bits wide (36 with parity), but \par double-sided SIMMs have four RAS (Row Address Strobe) lines \par instead of two. This can be thought of as two single-sided SIMMs \par wired in parallel. But since there is only one set of data lines, \par you can only access one “side” at a time. Usually, 1Mb, \par 4Mb, and 16Mb 72-pin SIMMs are single-sided, and 2Mb, 8Mb, and \par 32Mb SIMMs are double-sided. This only refers to how the chips \par are wired– SIMMs that are electrically “single-sided” \par may have chips on both sides of the board. Most 486 motherboards \par use memory in banks of 32 bits (plus parity), and may treat a \par double-sided SIMM as “two banks” (see your \par motherboard’s manual for details). Some can take four SIMMs if \par they’re single-sided, but only two if they’re double-sided. \par Others can take four of either type. Pentium (and some 486) \par motherboards use pairs of 72-pin SIMMs for 64-bit memory. Since \par double-sided S
