Undervolted AMD K6-III+: 400 to 600 MHz

Рет қаралды 9,529

Жыл бұрын

In this video, we are going to reduce the voltage of the modified AMD K6-2+ to just enough to be stable.
There will be a minimum voltage for frequencies from 400 up to 600 MHz.
Join me in this journey to finally know how low AMD's mobile CPUs could be undervolted!
You can support me on Patreon:
/ bitsundbolts

Пікірлер: 71

@lemagreengreen Жыл бұрын

Is there a good explanation for why AMD and Intel were running chips at significantly higher than necessary voltages back in the day? I had no idea, undervolting really wasn't on my radar at all back when these chips were contemporary and we just wanted max performance, if anything overvolting was something we were more aware of and in some cases doing. I know with variables at play they maybe picked a 'safe' voltage and didn't want users playing with the minimums but still, it looks like they were using quite significantly more power than strictly necessary.

@bitsundbolts Жыл бұрын

Good question. I don't know. Will pin your comment, maybe someone has an answer. The gap between stable and stock voltage seems to be too large for the silicone quality argument.

@graealex Жыл бұрын

I would assume that some dies would run stable at certain voltages, while others wouldn't. You'd either have to decrease yield, or do some type of binning if you wanted to utilize some dies being stable at lower voltages. Here, the sample size of dies is literally just one, so who knows how the majority of dies, especially the early ones, did perform. And even for this single die, you can see that a stock core voltage of 1.8V might have been marginal, so 2.0V seems like a good and safe choice.

@xys007 Жыл бұрын

Probably because lower quality PSU's , single stage VRM's on motherboard etc, etc. which both contributed to higher ripples and noise in voltage, which affects stability. By increasing voltage you increase gap between maximum voltage that can be recognised as logical "0" and minimum voltage that can be recognised as logical "1". They could not guarantee motherboard quality back in the days, but they could increase voltage specification for CPU and have less unhappy customers returning their product. Additionally not every motherboard could be set for voltage this low with 0,1v steppes. By marking CPU voltage with 2 volts they made their product compatible with most motherboards available.

@Romerco77 Ай бұрын

That overclock at 1.7v has not been properly tested in this video, and imho it is probably not stable. The prime95 is a steady high load, and NFS3 with such a slow graphics card being the bottleneck running at what looks like 20 fps is not stressing the CPU at all. To properly test this old CPUs you need to use variable loads and high fps gaming for hours. I had a K6-3+@600 with voodoo3, and it was stable with prime95, games, etc, till one day i decided to play NFS2-SE from start to finish, that game runs at like 160 fps in my CRT with that configuration, after 2-3 hours of gaming the instability started to kick in, and finally I had to reduce a bit the CPU clock.

@dolphhandcreme Жыл бұрын

The reason why higher frequencies generate more heat is simple: With every clockimpulse, the transistors have to shift signals from 0 to 1 or vice-versa. The parasitic capacitance of the whole circuit acts like a short-circuit, for a fraction of a microsecond. Thus, the more often you switch, the more often you "short" the circuit and generate heat. Like charging a capacitor trough a battery and then reversing polarity, only for discharging and recharging it the other way around.

@toseltreps1101 Жыл бұрын

geiler Name, Christoph Stirnlappen hier

@3dfxvoodoocards6 Жыл бұрын

Interesting video, like !

@bitsundbolts Жыл бұрын

Thanks!

@P2PC Жыл бұрын

Wow. You have gone above and beyond with this video! Edit: Typo This really emhasises how much voltage headroom was in older cpus compared to modern ones. I did some rough back of the napkin math (not counting power draw) voltage/frequency scaling with your minimum voltage data @10:17. Simple equation (Frequency/voltage = arbitrary scaling value) The higher the scaling value the better the scaling. (highest is best) 400Mhz/1.3v=307.69, 450Mhz/1.3v=346.15, 500Mhz/1.35v=370.37, 550Mhz/1.5v=366.67, 570Mhz/1.55v=367.74, 600Mhz/1.7v=352.94 We can conclude that around 500Mhz @ 1.35v was likely the V/F 'sweet spot' for your K6-II+ (Technically K6-III+) CPU. (my results may be flawed but it gets a good idea of the V/F curve) Of note, we can observe that 600Mhz @1.7v the V/F scaling begins to decreace significantly from 570Mhz @1.55v. This begins to idicate the limits of your silicon. You do amazing work here BuB! Keep at it!

@bitsundbolts Жыл бұрын

Thank you for taking the content further! I think you're spot on with your calculations - and that is probably why AMD stopped at 570 and not 600 MHz. Maybe my CPU sample is a later one with "good" quality since I could unlock the level 2 cache without issues.

@P2PC Жыл бұрын

@@bitsundbolts You could very well be on to something here. I have a suspicion that AMD took (at least some) full K6-III+ dies with 256kb L2$ and locked them down the cheaper K6-II+ with 128kb L2$ just to move sales volume despite the chips being fully functional with their cache. We’d probably need a larger sample size to confirm that though. Regarding further V/F scaling, a real K6-III+ would need to be compared to for sake of scaling comparison. Keep up the awesomeness BuB!!

@Bruno-Guitarist 5 күн бұрын

Overclocking was fun back in the day..

@Neksus-M06 Жыл бұрын

I like where this is going. :) Undervolting: a saga.

@TyrKohout Жыл бұрын

Great video! I love seeing old CPUs being optimized to their ideal performance point. I'd like to see a video of this CPU in a different motherboard being pushed to the temperature limit with sufficient cooling. You might be able to squeeze 750Mhz or more from it!

@bitsundbolts Жыл бұрын

I'll get two more SS7 motherboards soon. Will try to get as far as possible depending on overclocking capabilities. Thanks for watching!

@surfin7 Жыл бұрын

Nice!! I have a K6-III+ 400 somewhere around here, will try to get it and play when I have some time 👍

@GraveUypo Жыл бұрын

back then i gave absolutely zero facks about undervolting or underclocking, overclocking was still an exploit and not a feature, so it was actually worth it. when my second athlon cpu broke, i was forced to use a pentium 2 400mhz for a while. i ran that thing at 600mhz for about half a year straight. performance was actually pretty decent. completely usable even stepping down from a 1.1ghz athlon. obviously it wasn't anywhere near the same level, but it still allowed me to play my unreal tournament with decent performance in most maps. poor thing certainly wasn't comfortable at this speed though. 150mhz bus speed meant most pci cards wouldn't even work. the ideal overclock for it was 533mhz, everything still worked at this speed. that cpu still lived for a good 10 years as an office pc after i was done with it. still overclocked to 533 the entire time.

@martinnielsen154 Жыл бұрын

Fantastic job. cool video 💪

@bitsundbolts Жыл бұрын

Thank you!

@PauloRAgostinho Жыл бұрын

Nice vid and explanation! It makes sense to be able to do 1.7V, since the CPU is 0.18nm (like the P3 Coppermine).

@recnas Жыл бұрын

Nice video! If included in the Kernel the Linux powernow-k6 driver is actually capable of dynamically scaling the frequency by altering the multiplier during runtime even on desktop motherboards.

@ClassicTrialsChannel Жыл бұрын

miss my overclocking days. 95 to 2006 when I stopped making my own PCs.

@BlueSkyYGO Жыл бұрын

Super nice!

@tigheklory Жыл бұрын

I have a DFI 586IPVG that I bought back in the day, it has the VX chipset not the VIA chipset, but it was awesome back in the day having USB so early. I used it for a very long time, and I am going to put it back together soon.

@exxor9108 Жыл бұрын

This video, I very much enjoyed. xD

@bitsundbolts Жыл бұрын

I am glad you enjoyed the video. Thanks for watching!

@utubeuser1024 7 ай бұрын

I had a K6-III+ on a Gigabyte 5SMM motherboard in around 2006 - this board not only was able to run at 133MHz FSB on Super 7 but it slso had voltage options from 1.3-2.05V in 50mV increments as well as 2.0-3.5V in 100mV increments. I ended up putting an AMD K-6III+ 500ATZ (1.6V nominal voltage) and managed to run it at 3x133 MHz for 400MHz and at just 1.3V - it ran without a heatsink or fan and reached 52C load according to the motherboard temperature sensor

@bitsundbolts 7 ай бұрын

Wow - passive cooling without a heatsink! The 52C sound like it is close to the limit those CPU were meant to run at. But I guess the CPU survived it?

@utubeuser1024 7 ай бұрын

@@bitsundbolts yep the CPU ran like that for more than a year. I still have the CPU around here. I put my finger on the heat spreader while it was under load and i could rest it there for several seconds. Also, all the K6+ CPUs that I have seen are rated to 85C (the Z at the end of the model number indicated 85C) - the non Plus chips were more like 60-65C instead)

@Jack7277 Жыл бұрын

man, you are sick ))))

@bitsundbolts Жыл бұрын

I'll take this as a compliment ☺️

@Jack7277 Жыл бұрын

@@bitsundbolts yes sir, it is

@exxor9108 Жыл бұрын

I'm interested in seeing what kind of benchmarks you can get with the K6-II+ when its fully unlocked.

@bitsundbolts Жыл бұрын

I'll do videos on this CPU in the future.

@lordmmx1303 Жыл бұрын

first :) also, i own 500Mhz variant with OC to 600Mhz. Never tried to get it higher.

@bitsundbolts Жыл бұрын

I've read that more than 600 MHz is really not worth it. You probably get the best result somewhere between 550 to 625 MHz for those CPUs.

@lordmmx1303 Жыл бұрын

@@bitsundbolts that sounds possible. I think i have seen a board that could do 103mhz or 112mhz fsb for ss7 but that was about it so there's not really a room for more overclocking.

@bitsundbolts Жыл бұрын

Yes, it totally depends what the board supports. I have two other boards that may be able to do this, but I'll only get them next year. If one of them supports higher FSB speeds, I'll try to get higher with this CPU, but I have a feeling it won't make it past 625 or so.

@primus711 Жыл бұрын

@@bitsundbolts i ran mine over 650 700 was a no go

@bitsundbolts Жыл бұрын

In case one of the other two SS7 motherboards support proper overclocking settings, I am going to attempt an overclock as well!

@argoneum Жыл бұрын

When I was playing with my K6-II+ it used to fail in 3D-Now! calculations at 600MHz, no matter the voltage. Otherwise it would work ok. Also a 570MHz part, kept it running at 550MHz though.

@bitsundbolts Жыл бұрын

Testing for stability is hard. I prefer to use the CPU in regular day-to-day workloads. If random crashes occur, something isn't right. But good point on specialized instructions, they may not be used in benchmarks and so the illusion may appear that the CPU is stable until you fire up a 3DNow! application.

@thumbwarriordx Жыл бұрын

Honestly more of them back in the day should have seen the writing on the wall with speed scaling. All the CPUs do it now. Both up and down from nominal clockspeed. You've actually gotta go in and turn it off on desktops now if you don't want it.

@fradd182 Жыл бұрын

So, they had 0.45V reserve for the stock speed. I would never expect that, its huge. Maybe 0.1-0.15v is to be expected, but this...

@Neksus-M06 Жыл бұрын

Exactly my thought.

@bitsundbolts Жыл бұрын

I don't have one, but I think there were K6-III CPUs that had an engraving of 1.6 volts. We already know that AMD used the same die for K6-2+ and K6-III+ and artificially limited their lower tier models. Maybe they just didn't care about the updating the aluminum heat spreader at that point...

@nicholsliwilson Жыл бұрын

Oh I’ve taken a K6-3+ way lower. Every time I turn the laptop off it goes down to 0v.

@0371998 Жыл бұрын

Hi Mister, Where have you got a true 600 mhz ?

@bitsundbolts Жыл бұрын

I am afraid to say, it is fake :) just my skills with a photo editing software... It is a K6-2+ 570.

@Tubby.1 Ай бұрын

Wenn ich mich richtig erinnere wurde der K6-3+ 400 sogar mit 1.6V CORE in Embedded Systemen verbaut

@bitsundbolts Ай бұрын

Ja, da gibt es ein paar Modelle die offiziell bei so niedrigen Voltzahlen laufen. Ich glaube aber nicht, daß es da gravierende Unterschiede gab - vielleicht etwas binning.

@ruthlessadmin Жыл бұрын

That's crazy. Back in the day, I had a 300mhz K6-2 (no +) and don't think I ever tried to OC. I wonder how much performance I left on the table, while still running a space heater....

@bitsundbolts Жыл бұрын

Probably they had some headroom, but they were also manufactured in a larger 250nm process whereas the + versions were created using 180nm. So, your milage may have been limited. But I do read many posts in forums where owners complained about their K6 CPUs being slow and hot.

@ruthlessadmin Жыл бұрын

@@bitsundbolts Ah...did not realize the process change between the parts. I have recently added some K6-2 CPUs to my collection, as well as the same mainboard I used back in the day. Sounds like a fun experiment!

@bitsundbolts Жыл бұрын

If you find a good deal on the mobile versions, don't think twice to get one. They run much cooler. The K6-III (non +) used the 250nm manufacturing process as well (=they get hot)

@John_Doe1980 Жыл бұрын

i had hoped it would allow you to run it at 750mhz plus since it was so good with voltage drops in the chart

@bitsundbolts Жыл бұрын

I haven't done overclocking on those CPUs yet because the motherboard doesn't allow for higher than 100 MHz FSB. Once I get a board that can do that, I'll try to see how far this CPU can go. But from what I've read, it will be difficult to get much further than 650MHz.

@John_Doe1980 Жыл бұрын

@@bitsundbolts ah right I thought the thermal head room you had was the limiting factor

@0371998 Жыл бұрын

If only the Super socket 7 had an official mvp4 chipset with a true Agp slot, a true 133 mhz support. 6x133.3 mhz = 800 mhz !

@bitsundbolts Жыл бұрын

Even if it could, I don't think there would be any CPU that could run at those speeds. The K6-2+/K6-III architecture reached its limits at around 600-650MHz. At least this is what I have read.

@ashrafatteya Жыл бұрын

change crystal osc with higher one. this cpu can run up to 800MHz with higher frequency crystal osc but it tricky with isa

@JessicaFEREM Жыл бұрын

but could you overclock it as much as it'll go

@bitsundbolts Жыл бұрын

I need a different motherboard with good FSB overclocking support to go beyond 600 MHz. This is all I could do with the DFI board. I read somewhere that there may be a possibility to do it via software, but I haven't checked this yet.

@JessicaFEREM Жыл бұрын

@@bitsundbolts that's fair undervolting is probably what you want anyways if you want to reduce the power of your old machine.

@bitsundbolts Жыл бұрын

I may replace the heatsink with a smaller one and run this CPU around 500-550 MHz. Way less heat to dissipate now. As you said, this is a possibility to keep those old CPUs cooler and last longer.

@user-zx5mo1zf9v 8 ай бұрын

НАСКОЛЬКО Я ПОМНЮ ТАМ БОЛЬШЕ 550 МХЗ НЕ ОТОБРАЖАЕТСЯ. MORE THAN 550MHz LIMETED TO SHOW IN MAINBOARD ~VIA 512 WT-CACHE.

@CHA0SHACKER Ай бұрын

Jesus, my K6-III+ needs 1.8V for 550MHz and 2.4V for 600MHz if i want stable operation. It really doesn't like 600MHz

@bitsundbolts Ай бұрын

Wow, that jump to 2.4 volts for an extra 50 MHz is painful! Silicone lottery. You should probably keep your K6-III+ at 550 MHz and call it a day. There isn't much benefit from those extra 50 MHz. At least not when you need to run that processor at 2.4 volts.

@CHA0SHACKER Ай бұрын

@@bitsundbolts Yeah i figured as such. Most likely because it's a 1.6V 400MHz model that is more binned for low power than high clocks. 550MHz was the highest frequency these were sold at anyway, so I'm quite happy.