Challenge: upgrading old Cyrix PR-200 box to K6-2@500

[HamsterX]

Here's a good challenge for the hardware hacker that lives in all of us :

I'm attempting an upgrade to old CyrixPR-200 PC built over a Soltek SL-53D5 Socket7 VIA VPX motherboard (NOT the SL-53D5-s) with a newer AMD 500 MHz K6-2 CPU. OK, stop laughing , this is not my main PC

The K6-2 can easily be configured to run at 6x83 MHz = 500 MHz by setting the jumpers to 83 MHz FSB and 2.0x clock multiplier, the CPU itself translating 2.0x to 6.0x. The catch is the VCORE voltage, which at 2.8 V is too high for the 2.2 V required by the CPU.

Is it possible to configure the jumpers, or modify/hack this motherboard so that it can feed the CPU with 2.2 V ?

Any hardware hackers out there ?

[HamsterX]

OK, boys... I FOUND A SOLUTION

Thanks for reading

[BearCat]

Nice 2 see I'm not the only one playing around with old HW

But please, let us know the sollution to your problem.
It might help the next one who are trying to do the same.

I did this trick with an old computer, using a Asus TX97-X mb.
When it was "new" it had a K6-200 ( not k6-2 ), and now it runs with a K6-2/450 @ 500.
Booting W2k takes some time, but it's rock steady for use as a " typewriter / surfboard "

[HamsterX]

Sorry, really I should have posted the "solution"... the trick is explaining it with text-only

-----------------------------------
I used a trick almost identical to the hack of the FIC PA-2012 mobo.

Here's the method:

The voltage regulator jumpers look like a row of say 6 double pins. A jumper in these pins selects 2.7V , 2.8V etc. There are resistors placed aside the pins in the PCB.

This is a sample:

-R5--o o-- 3.5V
-R4--o o-- 3.2V
-R3--o o-- 3.0V
-R2--o o-- 2.8V
-R1--o o-- 2.7V

All we need is a multimeter to measure the resistance of each resistor. Then we plot V vs. R in Excel we see that lower VCORE needs higher Resistance and use the graph for extrapolating (log function) the resistance needed for 2.2 V (K6-2 VCORE).
Sample: if the extrapolated calculation gives 2.2V = 560 ohm and the resistor aside the 2.8V jumper, for example, is 230 ohm, all we need is to attach a 330 ohm resistor closing the pins of that jumper (230 + 330 = 560).

For details check this link:

_http://www.geocities.com/hackedmobo/pa2012/pa2how.htm#top

The ASUS P/I P55-T2P4 mobo also features that 5 row-double pin VR, but works in a different way, and it's much easier to hack

_http://www4.tomshardware.com/howto/00q3/000725/
_http://www.jump.net/~lcs/kalle/

Also useful this one:

_http://surf.to/ga586hx
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[pmi]

Now I have another question..

I have a Cyrix M2 PR300 on a Intel VX board, at 3.5x66 MHz... That is the top i can get from that board. Is there any way I can get a higher bus then 66 MHz? Or some other way to be able to put a better CPU......

Thanks.

[HamsterX]

Hi

What brand and model is your motherboard ?

To see if your motherboard supports 75+ MHz FSBs, you'll have to check the manual, the motherboard prints in the PCB, the web... FSBs higher than 66 are not supported officially with the 430VX chipset... they're usually hidden or undocumented.

"Better CPU" ? Well, in this thread we're talking about refurbishing an old mobo with a K6-2 , K6-III or K6-2+ running at 6x66=400, 6x75=450 or 6x83=500 MHz.

To my knowledge there's no other cheap way to fit these old Socket7 mobos with better CPUs. And it's now very, very difficult to find a K6... maybe in the online auctions ?

Here's what you need:

1) A K6 CPU with CXT core (last K6-2's, all K6-III and K6-2+). This CXT core "translates" the 2.0x clock multiplier to 6.0x
2) A motherboard able to supply 2.0 to 2.2 V (or in some way "hackable")
3) Some luck The mobo I'm using is somewhat useless because no more RAM can be added... the actual SDRAM DIMMs are misbehaved with old mobos...

Cheers

HamsterX

[pmi]

Thanks...
I've been reading those links and I have a good ideea of what I have to do. Is just that I need a second opinion.
I have a ZIDA board, 5SVX, with VX chipset. It goes up to 66MHz bus, 3.5 multip. I have 96 MB Edo RAM...a trident blade 3d on it (8 mb ram)... The clock chip can go up to 75 MHz, but I couldn't do it from jumpers. It seems to me that I can make it only to go to 6x66 MHz= 400 MHz. And yes, the cpu... i have to find a second hand...

[nnuxx]

hehe... e eu q pensava q os portugas eram os únicos... bem jogado

that's all folks