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Getting more 2.0v?
If I feed it more 19v, what breaks next?

New MessageGetting more 2.0v? (modified 0 times) n6mod
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I think I've read everything that's been written about putting AMD K6-2 and K6-3[+] processors in iOpeners, but I want to make sure I've got it:

New iO's (v4, v5) have Split-Plane enabled, and if there's a mP6 they're already set to Vcore=2.0v.
Older iO's (v1, v2, not sure of v3) require a mod to enable Split-Plane.

Max ICCcore for a K6-3+ is 8.5A, compared to 2.0A for an mP6. The stock Vcore supply is set to limit somewhere around 6A, hence the mods to the sense resistor.

The current limit exists to keep Q16 from setting the board on fire. If you can cool Q16, either with a heat sink or by adding dropping resistors between it and the 3.5v supply, the next weak link is the iOpener power brick.

This is all established art, amounting to the the Turbo3 mod, with credit due to others along the way. So, going forward:

Where is the limit to what the 3.5v supply can provide?

I have some 2.4A@19V supplies around (IBM WorkPad) and I think that there are other ThinkPad supplies that are even beefier. For instance, the Lind Electronics auto/air adapter for the older ThinkPads can source 3A at 19V.

Any thoughts?

01-02-2001 12:59:02

New MessageRE:Getting more 2.0v? (modified 0 times) Linuxguru
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The Rise MP6 has a Vcore of 2.8 v. If you have switch SW4 (present on most V4 and all V5 units), then you can set Vcore to 2.0 v.
01-02-2001 13:51:46

New MessageRE:Getting more 2.0v? (modified 0 times) n6mod
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The Rise MP6 has a Vcore of 2.8 v. If you have switch SW4 (present on most V4 and all V5 units), then you can set Vcore to 2.0 v.

That's what I get for reading the datasheet instead of looking at the board. (I'm at work, my iO's are not). The data sheet here pretty clearly states a Vcore of 2.0v. (and ICCcore of 2A@250MHz). This probably means that the iO isn't using the .18u version of the mP6.

But I know we can get 2.0v, the question is how can we get 8.5A of it. If I do the Turbo3 mod with dropping resistors, put a waterblock on Q16, and hook up a 19v supply that can source a couple extra amps, can the 3.5v supply that feeds Q16 hack it?

01-02-2001 15:50:57

New MessageRE:Getting more 2.0v? (modified 0 times) Turbo3
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I use a power brick from Jameco ($20) which is rated for 2.5A @20v and has the added advantage of running on 50/60 Hz 100-240v. To answer your question, the inductors, caps, and mosfets for the 3.5v supply would be the next breaking point in addition to even more waste heat from the dropping resistors and Q16. The max current I have been able to pull from the 3.5 is a little over 7A. After that the undervoltage protection cuts in as the voltage sags. But why do it? The K6-III+ runs just fine on 1.8 volts at 500MHz with a FSB speed of 100MHz. You are not going to see much real world performance increase with just higher multipliers for the CPU. It might be possible to run at 550MHz by picking a different vcore than 1.8. At 1.8v and 550MHz the system is not stable and will get program exceptions after running for a short time. At 500MHz it runs perfectly under all conditions. It appears to me the disk subsytem is the next weak point and not the CPU performance. You would probably only see an improvement in benchmark numbers that only test the CPU but not in real world programs.
01-02-2001 18:58:27

New MessageRE:Getting more 2.0v? (modified 0 times) n6mod
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Turbo3-

Thanks for the reply. The K6-III+'s I have are only 450's anyway, and I was hoping to run at 4.5x100MHz.

I'm a little surprised that you are getting such good results at 1.8v, though. I tried one of the K6-III+'s in my Scovery at 1.8v and it would POST but wouldn't boot. The case markings are as follows:

AMD-K6-III+/450ACZ
2.0V CORE/3.3V I/O
A 0029BPMW

Is there a different flavor of K6-III+ I should be hunting for this application?

It will be a week or so until I get time to tear into the iO's and try one there. Thanks again for the input!

-Z

01-02-2001 23:47:43

New MessageRE:Getting more 2.0v? (modified 0 times) Turbo3
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Mine are also K6-III+ 450MHz overclocked to 500MHz. The markings are the same except the batch number. Mine are A 0024BPAW.
01-06-2001 22:45:05

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