Apple Macintosh Performa 6400 Series - Manual (Page 167)

You can increase your computer’s DRAM to up to a maximum of 136 MB.
Your computer already comes with 8 MB soldered on your computer’s main
logic board plus 8 MB installed in one of the DIMM slots, for a total of
16 MB of DRAM. One DIMM slot remains for installing an additional 8-MB,
16-MB, 32-MB, or 64-MB DIMM, for a total of 24 MB, 32 MB, 48 MB, or 80
MB of DRAM respectively. (If you want to install the maximum amount of
memory, you need to replace the 8-MB DIMM already installed in one of the
DIMM slots with a 64-MB DIMM, and then install a 64-MB DIMM in the
remaining slot, for a total of 136 MB of DRAM.)
IMPORTANT The DIMMs should be 64-bit wide, 168-pin fast-paged mode,
with 70-nanosecond (ns) RAM access time or faster and a 1K or 2K refresh
count. The Single Inline Memory Modules (SIMMs) from older Macintosh
computers are not compatible with your computer and should not be used.
DIMMs that support a 4K refresh count also should not be used.
If you decide to have additional DRAM installed in your computer, the
DIMMs can be installed one at a time in any order in either of the
memory slots.
High Performance Module configurations
A High Performance Module (level 2 memory cache) provides an overall
increase in your computer’s performance. Although the megahertz processor
speed stays the same when you install a High Performance Module (see your
Technical Information booklet for the exact speed), your computer performs
tasks significantly faster with a High Performance Module installed. You can
add a High Performance Module by installing the module on the main logic
board of your computer.
Installing the DIMM or High Performance Module
Installing memory involves three steps:
m opening the computer
m inserting the DIMM or High Performance Module into a specific slot
m closing the computer
167 Installing Additional Memory