I've sent these instructions to the coreboot mailing list as well:
http://coreboot.org/pipermail/coreboot/2008-June/035915.html
http://coreboot.org/pipermail/coreboot/2008-July/036716.html

From: Peter Stuge <peter@stuge.se>
Subject: [coreboot] GA-M57SLI-S4 rev 2.0 dual flash chip modification recipe

The board can be modified in two ways. One is simpler and less
reliable, the other is more complex but much more robust.

Material needed:
1x SO-8 SPI flash chip, ideally 200mil but 150mil can work too
   Spansion S25FL016A is easy to get, Macronix has the 32Mbit MX25L3205.
2x 0402 100k chip resistors
1x SPDT (Single Pole Dual Throw) switch and three wires

For the better modification, you also need:
2x 0402 4k7 chip resistors (1k is OK too, 10k does not work!)
2x 0603 100k chip resistors
2x SOT-23 BC847C transistors
1cm AWG 30 wire (but get some extra so there is some to work with)


See m57sli_soic_detail_labels.jpg for reference.
Common steps always needed:
1. U9: Populate flash chip.
2. R509: Remove.
3. R89,R130: Populate 0402 100k resistors.

Simple:
NOTE: Keep wires to the switch short! Only a few centimeters/one inch.
4. Solder center contact on switch to Q4-3 or Q5-3. Either is OK.
5. Solder one side contact on switch to Q4-1.
6. Solder other side contact on switch to Q5-1.
7. DONE!

Better:
NOTE: Switch wires can be long. Several meters has been tested.
4. R90,R91: Populate 0402 4k7 resistors.
5. Q2,Q43: Solder 5mm or so of AWG 30 wire between Q2-2 and Q2-3.
           Solder another wire between Q43-2 and Q43-3.
6. R86,R389: Populate 0603 100k resistors.
7. Q4,Q5: Populate SOT-23 BC847C transistors.
8. Solder center contact on switch to VCC, e.g. at BC54-2.
9. Solder one side contact on switch to R86-2.
10. Solder other side contact on switch to R389-2.
11. DONE!

I am happy to sell boards pre-modified with the better modification.
Unfortunately I cannot offer these boards to consumers in all EU
member states because of EU environmental regulations, but many are
OK.

//Peter
Member stateConsumers?Businesses?
AustriaOKOK
BelgiumOKOK
BulgariaOKOK
CyprusOKOK
Czech RepublicOKOK
DenmarkSorryOK
EstoniaSorryOK
FinlandOKOK
FranceSorryOK
GermanyOKOK
GreeceSorryOK
HungarySorryOK
IrelandSorryOK
ItalyOKOK
LithuaniaOKOK
MaltaOKOK
NetherlandsOKOK
PolandOKOK
SlovakiaOKOK
SloveniaOKOK
SwedenOKOK
Latvia,
Luxembourg,
Portugal, Romania,
Spain and the
United Kingdom
Sorry :\

This is what a finished better modification looks like: (click for large version)


m57sli_soic_detail_labels.jpg is a closeup of the relevant part of the board with components labeled.
You will need this if you want to do the modification yourself.


Below are some photos demonstrating the principle for the simple modification:
The following photos by Peter Stuge are placed in the public domain.
overview.jpg  overview of how the switch and resistors should be connected to U5 and U9
U5.jpg        detail of the switch and resistor connections at U5
U9.jpg        detail of the switch and resistor connection at U9