hardware fixes
Adding BF2 jumper on older Socket 7 mainboards
Most older mainboards featuring Socket 7 were designed for processors available
at RTM schedule (RTM - release to market). Therfore manufacturers thought not
of implementing multipliers higher than 3.5x because intel's flagship processor
this time was a Pentium 233 MMX. It was designed to run with a 66MHz FSB (FSB
- front side bus) and a multiplier of 3.5x (3.5x 66MHz = 233MHz). A Pentium MMX
CPU has a maximum multiplier of 3.5x although some notebook versions (Tillamook)
feature multipliers up to 4.5x but were manufactured using a different socket
format (MMC - mobile module cartridge).
Later AMD introduced Socket 7 processors (K6, K6-2, K6-III) with frequencies above
233MHz (reaching up to 550MHz with K6-2 and K6-III). To get support for these
higher multipliers AMD used an additional pin on Socket 7 named BF2 and raised
supported front side bus to 100MHz. The resulting specification for Socket 7 was
called Super Socket 7 (or SS7). But as Socket 7 and Super Socket 7 have the same
layout you can add BF2 to your Socket 7 board with some simple wiring.
Two options are available:
Connect BF2 permanent (easy way) to ground (V36) or connect BF2 to ground (V36) using a jumper
(requires some soldering). Keep in mind that status of BF2 is only of interest for processors
aware of BF2 like AMD K6, K6-2, K6-III or Cyrix MII or IDT WinChip. Intel Pentium
MMX, AMD K5 and rise mP6 ignore BF2. See the following table for the resulting
effects:
For a full list of all Socket 7 processors refer
to this page. You don't need to modify your board if you want to use a multiplier
of 6.0x as this is available by using the 2.0x multiplier (AMD K6-2 CXT and K6-III
interpret 2.0x as 6.0x due to a different implementation by AMD).
Normal
(no BF2)BF2 full
connectBF2 jumper
connect
BF2
BF1
BF0
0
0
0
2.5x
2.5x
0
0
1
3.0x
3.0x
0
1
0
2.0x
2.0x
0
1
1
3.5x
3.5x
1
0
0
4.5x
4.5x
1
0
1
5.0x
5.0x
1
1
0
4.0x
4.0x
1
1
1
5.5x
5.5x
Bottom view of Socket 7
AN O O O O O O
O O O O O O
O O O O 1
O O
AM O O O O O
O O O O O O
O O O O O O
O
AL O O O O O O
O O O O O O
O O O O 2
O O
AK O O O O O
O O O O O O
O O O O O O
O
AJ O O O O O O
O O O O O O
O O O O 3
O O
AH O O
O O O
AG O O O
4 O O
AF O O
O O
AE O O O | |
5 O O
AD O O |L|
O O
AC O O O | |
6 O O
AB O O |E|
O O
AA O O O | |
7 O O
Z O O |V|
B o t t o m
O O
Y O O O | |
BF0 --> 8 O O
X O O |E|
v i e w
BF1 ----> O O
W O O O | |
BF2 --> 9
O O
V O O |R|
O G
U O O O | |
O O O
T O O |
|
O O
S O O O |A|
O O O
R O O |
|
O O
Q O O O |R|
O O O
P O O |
|
O O
N O O O |M|
O O O
M O O |
|
O O
L O O O
O O O
K O O
O O
J O O O
O O O
H O O
O O
G O O O
O O O
F O O O
O O
E O O O O O
O O O O O O
O O O O O O
O O
D O O O O O
O O O O O O
O O O O O O
O
C O O O O O
O O O O O O
O O O O O O
O O
B O O O O O
O O O O O O
O O O O O O
O
A O O O O
O O O O O O
O O O O O O
O O
1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 3 3 3 3 3 3 3 3
1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3
4 5 6 7
Materials needed:
BF2 permanent connection:
- A print of this guide. (Sounds silly, but don't forget to print this before
you remove your Board ! )
- A short tiny wire OR
- A good temperature regulated soldering Iron with a tiny top. (choose ~325°
C) OR
- A conductive silver pen
BF2 connection with jumper select:
- A print of this guide. (Sounds silly, but don't forget to print this before
you remove your Board ! )
- A wire-wrap wire of 60cm length (also called enamel coated wire or Lackdraht).
That's a wire insulated only by paint.
- A desoldering pump.
- A two or three pin connector, that will act as a jumper, or just a little switch.
It may be a good idea to put a sticker near the CPU socket with a warning about your mainboard modifications !
How to
BF2 permanent connection:
- Use a short tiny wire (no isolation !) of approx. 1cm and stick both ends into the holes W33 and V36 depicted above. Insert CPU. Ready.
- Use soldering iron and wire to connect pin W33 and V36 at the bottom of the Socket 7 as depicted above. Ready.
- Use a conductive silver pen to connect pin W33 and V36 at the bottom of the Socket 7 as depicted above. Ready.
BF2 connection with jumper select:
Get the wire and remove the isolation from the end and solder it carefully to pin W33. Connect another wire to pin V36. Solder other ends of the wires to your
switch or jumper. Now you have to decide where to put the jumper !
I decided to use some glue to put it near the existing multiplier jumpers. Please watch out not to build any connections to existing wires on the mainboard which
would cause shortcuts.