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On July 20, 1998 John Rinehart wrote:

To go back to the original question that I asked, I would like to upgrade the
memory on an older Packard Bell system.  The system has an AMI MB and BIOS.
The chipset on the MB is an Intel Neptune chip set 82433NX (LBX), 82434NX (PCMC)
, and 82378ZB (SIO.G).

Information in Packard Bell's WEB site states for this system PB550:

1. SIMM speed must be 70ns or faster.
2. The SIMMs are 72-pin and can be x32 or x36. The motherboard design does not
require parity checking  The motherboard will not use EDO,
only Fast Page Mode SIMMs will operate correctly in this motherboard.

And yet Scott Mueller's Upgrading and Repairing PC's states on page 803
paragraph 2 of the 8th edition, "You can install EDO memory in older systems
that do not support it because EDO is backward-compatible with standard (called
fast page mode) memory."

Sincerely, John

I can't argue with your experts, but I have never had a motherboard pass the POST
test with EDO accidently installed when the motherboard specifically stated fast
page mode ram was required (and I have accidently done this too often, I admit.)
However, there are such things as auto sensing SIMM sockets, and I have several
Pentium boards using the VIA VPX / 97 chipset that can use mixed edo and fast page
as long as it is installed in pairs.  I also have two Taiwanese 486 socket 3 boards
of no brand name that I bought from an OEM and they support EDO and fast page
mixing.  Like most 486 boards the simms do not have to be installed in matching
pairs.
Tom Turak