IBM Expansion
1-8MB 286 Memory Expansion
4-14MB  Enh 80386 Mem Expansion (FDDE, FDDF)
   Identifying FDDF Old, New, and FDDE 
BOPT103.EXE - Upgrade SC.EXE and Mem Expansion ADF/ROM
   Functions of BOPT

1-8MB 286 Memory Expansion Adapter

ZM28-31, 39-41 30 pin SIMMs 

  This adapter provides 1MB of memory expansion with LIM EMS Version 4.0 support for all PS/2 Models 50, 50Z, 55 SX, 60 and 65 SX. 
       The PS/2 1-8MB 286 Memory Expansion Option is functionally equivalent to IBM's existing 2-8MB 80286 Memory Expansion Option (#8286, 6450609), but with 1MB of standard 85ns memory.  It is expandable in increments of 1MB or 2MB up to a maximum of 8MB by using 1MB SIMMs-85ns or 2MB SIMMs -85n. 

4-14MB Memory Expansion Adapter 

Ed Avis confides to the world:
IIRC there were three variants of the 2-14 card:

- without ROM: this writes IADF code to the MBR of the boot device.
Generally a bit of a pain and won't work with Linux (though I have
heard that it works if you use the Minix bootloader to boot Linux).  I
already have one of those cards.

- with ROM: this counts its memory at the same time as the planar
memory (like the 2-8 card does) and is easier to install.  Apparently
if you have one 'with ROM' card it can also take command of any
'without ROM' cards and let them work without needing boot track

Apparently there are two variants of the 'with ROM', I don't know if
there is any difference in use.

2-14mem.exe Files for 2-14MB 80386 Memory Expansion Adapter
@FDDE.ADF - IBM Enh. 80386 Memory Exp. Adapter w/ROM 
CFDDE.ADF - Init file for @FDDE.ADF 

Enhanced 80386 Memory Exp. Adapter 
@FDDF.ADF - IBM Enh. 80386 Memory Exp. Adapter 
CFDDF.ADF - Init file for @FDDF.ADF - required ! 
IFDDF.ADF - Init file for @FDDF.ADF - required ! 
@FDDF.ADF - IBM Enh. 80386 Memory Exp. Adpt alt file / more settings

J1-J4 72 pin SIMM socket U50 L1A4452

Supports 1MB, 2MB, and 4MB 80nS or 85nS IBM memory. 

Mandatory Replacement ENHANCED Enhanced 80386 Memory Expansion ECA 042

Identifying the FDDE, FDDF (old) and FDDF (new) Adapters
  All three share the same basic outline. The later Enh. 80386 Memory Exp. Adapter (FDDF new) has a single WHITE SIMM socket on the upper right. The FDDF card supports enabling or disabling Matched Memory. 
   The IBM Enh. 80386 Memory Exp. Adapter (FDDF old) totally lacks the resistor networks below the SIMM sockets. It only has two epoxy coated capacitors on the left edge (not three). 

  Which makes me wonder which came first. 
My Pocket Reference sez 

Option#  FRU #    Feature Code      Description
87F9856  87F0075  9856     4MB Mem Adpt (32 bit, 80nS)
87F9860  87F0075  2190     4-14MB Mem Adpt(32 bit, 80nS)

   Look below for the latest Enhanced memory adapter update- BOPT103.EXE, it will update SC.EXE and the BIOS ROM on your adapter. 

BOPT103.EXE (>16MB in a 70/80)

bopt103.exe BOPT103 Upgrade

Note - Your Reference Diskette MUST be:
50/60  version 1.06 or greater
55/65  version 1.04 or greater
70/80  version 1.10 or greater
70-486 version 1.04 or greater

   Reference Diskette update is most easily accomplished on a system with two 3.5 floppy drives. If a single drive is used, diskette swapping is required (may be as high as 55 swaps).
   In order for the new Enhanced Memory Adapter to boot up there must be
at least 1Meg of "free" memory below the 16Meg limit. If the sum
of system planar memory and any non-Enhanced Memory Adapter system memory is 16Meg or more, you must move some of that memory
to the Enhanced Memory Adapter (or remove it from your system) in order
to use the new Enhanced Memory adapter.

What does bopt103.exe do?

Peter woolgathers
  BOPT103 is a workaround to overcome the 16MB RAM limit on Mod.
 70/80 with the crippled DMA with using 1 x FDDE and 1 x FDDF card. It works - but it blocks two 32-bit slots .... leaving only one single 16-bit slot on a Mod. 70 ...
    In simple words the BOPT workaround asks you to install a maximum of 15MB on the systemboard and the FDDE card leaving a 1MB "adressing gap" for the memory on the FDDF card. This results in a total of 31MB in the best case. Don't know if a second FDDF card is also supported, but I don't think so.
     The better choice is to forget about the FDDE and FDDF cards and use e.g. a Kingston KTM-64000 or Acculogic Simmply RAM 32-bit card that have own memory mapper and error-detection logic. I have the Acculogic in one of my Mod. 80-A31 and have a total of 40MB installed. The KTM should be able to push the memory up to 64MB (8MB on the planar - 3 x 16MB + 1 x 8MB on the card) - but I haven't got the chance to test that. The Acculogic supports only 8MB modules. 

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