Interposer, geta, for 486 class CPU
486 CPUs in SX/DX/DX2 line made by intel work in 5V I/O
voltage. Intel DX4 and other High Power CPUs sold by Cyrix and AMD work in 3.3V to 3.45V I/O voltage.
In order to use such CPUs on PS/2 or PS/55, you need to use an interposer which switches down planar
5V to required voltage for those CPUs.
If you put a plain DX4-100 in your Bermuda or K/H complexes,
your CPU will get toasted in someday ( not immediately but slowly. I myself didn't imagine that DX4-100
would work with 5V supplied but it could work actually. Not tested with Cyrix or AMD though ).
These interposers usually have jumper blocks for
1) Multiplier selection,
2) WT/WB selection,
3) I/O voltage selection,
4) socket type selection
5) Intel/AMD selection.
Appropriate setting of an interposer for each CPU is needed to get full
potentiality of these high powered CPUs.
|But so far, your CPUs will not get toasted with *wrong* jumper setting
unless you put your
CPU onto the interposer with wrong orientation of pin #1 ( as far as
I know, 486/586 CPU will not get toasted with it. 386 and pentium
will immediately go to heaven ) or you erroneously set CPU off on "one-row"
beside correct position ( this will also send your CPU to heaven
at once ) . Of course I'd like to advice you DO not test
such stupid trial, OK ?
According to old PC magazines sold in 486DX100 era, there were compatibility
issue for interposers and DX4 and /or AMD/Cyrix. An interposer worked OK with DX4-100
on a system A but not good on system B. The other was OK on B but not on A.
One of PC
upgrade shops sold various versions of AMD upgrade interposers which were arranged to work
with specific model-types. I got one from
the shop for my 5551-NAB and it was designated as "tested on .......
PS/55 5551-NXB.... ". There was another model designated for IBM PC Master 100 and such.
These kits were cosmetically all same.
The shop did some tric or magic ot their products. Because I didn't know much about IBM products and
model numbers of PS/55s, I really worried if the kit for
NXB might suitable for my NAB or not.
Now I really feel strange that all of my interposers I had bought
very cheep or got free in as-is condition or as "junk" not
knowing about their specification worked fine on my PS/55s.
By the way, in Japan we commonly refer interposer
as "GETA". GETA means Japanese wooden made sandals. That's way I put it on the index.
|Don't know correct name of this product. I think this one
was contained in a CPU upgrade kit sold by JC world, one of famous
PC upgrade shop back in '97, but not so sure.
There were similar kind of interposers which looked like very close to
each other back in those days. I got mine to upgrade my 5551-NAB
and I am not sure if this is the one or not.
4x/3x/2x capable, Intel/AMD( dx4) selectable,
No jumper block for WB/WT
am5x86/Fan on DX4/2
J1: Multiplier for Intel CPU (
but including AMD 5x86 and Cyrix5x86 )
1-2 for 2x and 4x, 2-3 for 2.5X, open for 3x
J2: Multiplier for AMD DX4-80/100
1-2 for 2x , off ...dunno have no AMD486-120
J3: Voltage select
1-2 for 3.45V, 2-3 for 3.30V
|Once sold by Evergreen together with Cyrix5x86 100/4x, 133/4x .
A Japanese dealer sold it together with cache driver programs for
2) DOS/Win3.1 and OS2 ( Ver. unknown but most possibly Warp3
Seems et9603.exe by EverGreen contains same drivers set.
4x/3x/2x selectable, WT/CB( Cache Back?) selectable, Will
fit both on OD/Main socket.
Mine was given to me as-is condition, most of the outer pins were bent.
When I straighten pins,
4 pins around the corner were torn off !! Yo can see my poor
soldering work in the picture.
Due to this soldering rework. I can't use this one on LIF sockets on
complexes( any type but of course except Y ), on Bermuda or on 9585.
|| Bottom View
Cyric5x86-100/4x and EG Fan
3 pin block beside DC conecter
for a fan ; Clock multiplier:
Set jumper as designated on the PCB
3 pin block in the middle position ; Cache back
CB for W/B cache and W/T for Write-through
3 pin block at the corner ( opposite
to pin #1 ); Socket type select:
OD for Overdrive socket and the other for standard
ZIF or main socket.
am5x86-133 QFP package is soldered onthe PCB.
4x/3x speed selectable, WB/WT selectable, socket
position selectable for Normal/Overdrive.
Jumper block from left to righ
Left ; Socket type select:
OD for Overdrive socket and the other for standard ZIF
or main socket.
Center; Clock multiplier: left-center for
3x, center -right for 4x
Right ; L1 Cahce status, left-center
for WT, center -right for WB
4x/3x/2x selectable, WB/WT selectable,
Will fit both on OD/Main socket.
am5x86 with PL a heatsink/fan
DC connector for fan assy
is placed on the surface of the PCB.
Micro Switch block is placed
in the middle of pin side.
||Position 2 *
( Upper )
|Standard or ZIF socket
|| 2x, 4x *2
( Lower )
|O/D or 487SX socket
2 is ignored for a TI486DX4 and Cyrix 5x876 CPU.
selection for the TI486DX4 and Cyrix 5x86 CPU
is auto-detected by
system board doesn't support the WB function ( without a
socket ), the system BIOS will automatically set the
CPU to to run in WT mode.
for AMD-5x86-133 and Cyrix6x86-133 or higher.
for Intel/AMD/ST 486DX4-100 and Cyrix5x86-100
PL586 with am5x86 QFP ( newer type )
Not available now.
JC World Version
of am5x86 QFP
|This one is supposed to be a modified version of PL586. There
isn't any jumper blocks for speed selection or voltage. selection,
This one is fixed to 4x operation.
Special ROM is mounted inside pin block. JC world made several
versions for their products so that their interposers could be used on
various systems. Probably the ROM contains some implement to tease
the system ( CPU ID or something like that ? ) so that the Overdrive kit
can be used in various systems.
Due to presence of this ROM/Socket, This Overdrive kit doesn't
fit in several systems.
For example, ZIF socket in 5551-N or LIF socket on Type-4 N can't
accept this one.
|I'm not sure about this interposer. It's branded as "Buffalo";
known to you as Melco.
Designed to be used on ODP socket with a key pin ( 169 pin PGA
layout. see piture below in the middle ).
I think this one is mainly used for NEC PC98 series PCs. I don't
know how the jumper block works. But so far, it works on my PS/55s.
asically this is 3x capable interposer but there is unused register block
connected to R17 at the bottom side. It should be possible to remake it
to 4x(2x) capable interposer.
|Jumper Block Setting Hacking. updated
If my observation is correct, jumper Blocks JP3 & JP4 should be
set in combination of 1-2/1-2 and 2-3/2-3.
This interposer has no Voltage Selection jumpers nor Speed Selection
Probably this was designed to use an Intel DX4-100 and other
5x86 CPUs for
1) system which has only one ( MAIN ) socket
( doesn't matter if it is a
169-pin socket or 168-pin socket )
2) system which has a soldered QFP SX CPU with an ODP
B14 : UP# ( OUT ) for OverDrive CPU ( ODP )
||Connected to B14 at PIN side
|| Connected to Vss
IN ) for SX QFP & DX/DX2/DX4
C14 : FERR# for DX/DX2/DX4
|| Connected to C14 at PIN side
|| Connected to C14 at CPU side
|| Connected to A13 at PIN side
A13 : FERR# for ODP
| Jumper settings ( my presumption )
|| CPU layout & Socket Type
| Pins 1-2 Closed
|| Pins 1-2 closed
|| Main without SX CPU
| Pins 2-3 Closed
|| Pins 2-3 Closed
|| ODP Socket with a QFP SX
This one is very simple.
Really wondered if it could
handle 5x86 CPUs but it does.
Basically this is 3x capable unit. But it
is easy to remake it 4x operation with a simple soldering rework.
|Green rework wire
observed in the pics is not for 4x speed. It's for
ODPR CPU to be set in ODP socket. B14(UP#) was connected to
Vss. Then A13 should be
connected to C14 but I left it undone( I noticed most of PS/55 ODP
socket can take ODPR thus the rework was not completed ).
4x rework can be observed in middle pic. R17
connection to Vcc was disconnected
and rewired to Vss. ( usually R17 is
left open for 3x operation and is internally pulled up within
Click here for enlarged pic
in 77KB jpeg.