Gigabyte GA-586DX
update to AMD K6-2:

Hier vind je alle informatie die nodig is om je GA-586DX om te bouwen tot een
Dual AMD K6 type 2.  Soms gaan de performance vaak tot 80% omhoog!!! met een K6-2 200Mhz.
Als je een 400Mhz variant er in wil gebruiken zul je of een zwaardere voltage regelaar of 2 parallel
aan elkaar moeten zetten.

De K6 kan eigelijk geen multiprocessing. Het moederbord zal alleen met 1 CPU willen werken.

Met deze upgrade zal je de volgende problemen tegen komen.

  1. De GA-586DX ondersteunt dual voltage CPUs (P55C) maar alleen 2.8V core voltage. De K6-2
    heeft alleen een core voltage van 2.2V nodig
  2. Het moederbord heeft geen BF2 Jumper om een clock multiplier van meer dan X 3.5.
  3. De nieuwste BIOS ondersteunt K6, maar detect de K6-2 niet.

Probleem 1 (2.2V Core voltage):

The DX-Board has an autoamtic Dual-Voltage recognition. But it works only with 2.8V CPUs reliable. You can the put in the JP2 Jumper, or, even simplier, put in a bridge between Pin 1 and 2 of the Jumper. (Who wants to use 3.3V CPUs in these days) To get the 2.2 Volt core-voltage, you have to use a resistor of about 180 Ohm between pin 1 of the voltage regulator and ground ( Gnd-Pin of the cooler). This gives together with the parallel R32 (182 Ohm) and R148 (422 Ohm) a Regulator R1 of about 75 Ohm. Together with the resistor between pin 1 and 2 R33=100 Ohm you get the 2.2 Volt with the formula (75/100+1)*1.25 = 2.2V


The changes you have to do are marked green in the picture. red marks are for information only.

 

Measuring of the voltages:

If you use a load resitor of 100 Ohm between B16 and A17 in the CPU-Socket (in the pic to the upper right), you can measure the core voltage of 2.2V. At the resistor between B18 and A19 (lower right) one can measure the 3.3V supply voltage. (Don't regard the red and black in the picture, you measure between the ends of your resistor, of course). The third 100 Ohm resistor in the upper left is for switching to dual voltage.

CAUTION: before power on close the Socket! The voltage regulators should not be used without load (empty socket)!

The core voltage can be measured between pin 2 (or the housing of the VR) and ground.

The LX8383A on the GA-586DX is specified for 7.5A. This is normally enough for the K6-2. Peak-loads of up to 8.45A can be done with good cooling. If you get stability problems anyhow, you can use an LT1083CP (about 15 Euro) instead of the LX8383A and/or use an additional CPU-cooler for the voltage regulator.

Solution for Problem 2 (BF2 Jumper missing)

Bus frequency (66MHz)
CPU [MHz] factor BF0 BF1 BF2
233 3.5 1 1 1
133 2.0 0 1 1
200 3.0 1 0 1
166 2.5 0 0 1
366 5.5 1 1 0
266 4.0 0 1 0
333 5.0 1 0 0
300 4.5 0 0 0

The K6-2 300 is operated with the factor 4.5 (4.5x66=300) in 66Mhz Boards. As there is no BF2-Jumper on the DX-Board, you can use a little piece of loudspeacer cable between W35 and V36 in the CPU-Socket. Since you can use only one CPU, you can put the cable link in the other one.

You can put W35 to ground instead, if you don't like small wires on your board. BF0 and BF1 (Schalter 3+4) are both set (see pic):

 

Newer K6-2 starting from 400 MHz interpret x2 as x6, so you don't need to change anything regarding BF2. However, AFAIK still nobody suceeded in operating a 400MHz CPU or an K6-III with this frequency on the DX-Board. The maximum reported frequencies are 333 or 366 MHz. The problem seems to be the BIOS.

Solution to problem of 3 (BIOS detects no K6)

My DX board announces 486 DX60: -) I have the board revision 3b and the newest officially BIOS available with gigabyte (version 3.43).