Hi, Guys,
I'm not going to try to get very technical here, so I might be accusable ov
oversimplification, even to the possible detriment or what I'm saying here.
Since this thread is dealing with 30-pin SIMM sticks, we won't go into
72-pin versions here. As far as I know, there were no 30-pin EDO SIMMs
made, unless they were specially produced by a memory company like
Shenandoah Memory Systems in Virginia, who buy brand-name memory chips and
surface mount or solder them onto blank modules to order for some customers.
When considering SIMMs for a fast 80386 machine, or a 80486 machine, you'd
generally use ones speed rated for 80- 70- or 60NS. They could be
non-parity modules, even number of bits, in which case you would disable
parity checking in the motherboard's BIOS, or by setting a combination of
jumpers or dip switches, depending on the motherboard. There were true
parity SIMMs which had an extra bit always active for each 8-bits of memory.
There were also SIMMs that used parity emulation, in which there was an
extra bit for each of the 8 regular bits active only if one chip had an
error and the bit was slid over to the extra chip on the stick. Both the
true parity modules and the ones that used parity emulation have an odd
number of memory chips on each stick. A motherboard, such as the Compaq
DeskPro mother boards, and the Intel RapidCAD boards required the use of
true parity, and often fast-paging memory modules. Parity emulation would
not work, or at best would often return memory size and/or memory allocation
error messages.
IBM's PS/2 models required IBM PS/2 SIMMs, which often used different pins
for different addressing than standard SIMMs that worked in other machines.
IBM PS/2 SIMMs might not work in a non-IBM PC, although standard SIMMs with
IBM memory chips on the stick might work in a standard clone PC. Macintosh
memory chips will physically fit into the appropriate SIMM sockets of a PC,
but the system will most likely not recognize them as being installed.
There were so many permutations and combinations for banking, matching
and/or mixing various types of memory, as many as there were motherboards,
that you almost have to have documentation for that motherboard to know in
which order you may or may not plug which types of memory modules. You
almost must have documentation, unless you have a large number of every type
of SIMM made and are very careful and methodical in your testing, and have
lots of time on your hands to continuously swap out memory chips and writing
down all your combinations until you find the one that works.
I've never seen a 30-pin SIMM with more than 4MB memory chips on it, so if
the board has eight 30-pin SIMM sockets and no 72-pin ones, and if it can
accept 4MB SIMMs, then you max that board out at 32MB. The only way to get
more is to get one of those funky memory expansion cards like the Intel
AboveBoard 386, of AST's RAMPage 386 card of several other such ones that
were made. Then , you might be able to get all the way to 64MB on some
systems if you could find the cards that took 30-pin SIMMs.
Reply to: [EMAIL PROTECTED]
Brent Reynolds, Atlanta, GA USA
I have dynamic memory, it needs refreshing.
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