/\550 mhz/\

Get a slower one and overclock it.

I assume you already have a motherboard and you are trying to upgrade it to the max? The top end CPU for each platform will always attract a premium. The super-socket 7 platform on its own goes for stupid high prices.

Until recently, I didn't even know that 500 and 550MHz K6-III+ existed. I always thought that the K6 III+ topped out at 450, and if you wanted faster you had to step down to the K6-2+.

Just get one of those low voltage K6 III+ 400 chips and overclock it to 600.

mwdmeyer wrote on 2024-12-24, 05:15:

Get a slower one and overclock it.

I was thinking that. I've heard that the mobile chips are great overclockers. It's just one of those nice things to have I guess.

Anonymous Coward wrote on 2024-12-24, 06:03:

Until recently, I didn't even know that 500 and 550MHz K6-III+ existed. I always thought that the K6 III+ topped out at 450, and if you wanted faster you had to step down to the K6-2+.

Just get one of those low voltage K6 III+ 400 chips and overclock it to 600.

I might just stay with my k6-2 400 and Pentium mmx, as they're also quite expensive £130 delivered. If I need the extra performance I can just use my slot 1 or Socket A "PC's" (motherboard on a box)

james1998hodges wrote on 2024-12-24, 13:29:

mwdmeyer wrote on 2024-12-24, 05:15:

Get a slower one and overclock it.

I was thinking that. I've heard that the mobile chips are great overclockers. It's just one of those nice things to have I guess.

Technically speaking, ALL of the K6-2+ and K6-III+ chips are mobile chips.
I found my 450 for $20 on the big auction site several years ago. It hits 600 without a problem.
My K6-2+ chip came from and old Compaq laptop that I gave about the same for.

If you can't find one for a decent price, try sourcing one from and old K6 laptop.
But be aware they made most of them with both plus and non plus versions.

if you already didnt know, you can also mod a k6-2+ 'into' a k6-3+. think you get more cache if i remember correctly.

Jasin Natael wrote on 2024-12-24, 13:56:

Technically speaking, ALL of the K6-2+ and K6-III+ chips are mobile chips. I found my 450 for $20 on the big auction site sever […]
Show full quote

james1998hodges wrote on 2024-12-24, 13:29:

mwdmeyer wrote on 2024-12-24, 05:15:

Get a slower one and overclock it.

I was thinking that. I've heard that the mobile chips are great overclockers. It's just one of those nice things to have I guess.

Technically speaking, ALL of the K6-2+ and K6-III+ chips are mobile chips.
I found my 450 for $20 on the big auction site several years ago. It hits 600 without a problem.
My K6-2+ chip came from and old Compaq laptop that I gave about the same for.

If you can't find one for a decent price, try sourcing one from and old K6 laptop.
But be aware they made most of them with both plus and non plus versions.

Ok I thought low voltage ones were specifically binned for laptop though I could be wrong like the 1.6v 400mhz one

Joakim wrote on 2024-12-24, 14:30:

if you already didnt know, you can also mod a k6-2+ 'into' a k6-3+. think you get more cache if i remember correctly.

Yeah I heard that in a Phil's computer lab video but it doesn't work 100% of the time. I could give it a go

james1998hodges wrote on 2024-12-24, 14:35:

Ok I thought low voltage ones were specifically binned for laptop though I could be wrong like the 1.6v 400mhz one

The 2+ and III+ are all low voltage designed for laptop 😀 The lowest voltage ones were just spec'd to run at a slower speed simply for even lower power consumption (even if it got binned for that speed for some reason), but it's all the same chip at its heart. They can run faster, but likely too much power for the market they were designed for, so they never pushed 600 MHz.

james1998hodges wrote on 2024-12-24, 14:38:

Joakim wrote on 2024-12-24, 14:30:

if you already didnt know, you can also mod a k6-2+ 'into' a k6-3+. think you get more cache if i remember correctly.

Yeah I heard that in a Phil's computer lab video but it doesn't work 100% of the time. I could give it a go

The 1.6v and 1.8v variants run fine at 2.0v. Honestly the K6-2+s and III+s spec'd for lower voltages tend to overclock better than higher voltage variants with the same base clock speed.
That being said there is always some degree of luck involved. I have a 2.0v K6-III+ 450 running at 600mhz, but that is usually pretty rare and 550mhz is usually the stable limit for most.

3dnow wrote on 2024-12-24, 15:38:

james1998hodges wrote on 2024-12-24, 14:38:

Joakim wrote on 2024-12-24, 14:30:

if you already didnt know, you can also mod a k6-2+ 'into' a k6-3+. think you get more cache if i remember correctly.

Yeah I heard that in a Phil's computer lab video but it doesn't work 100% of the time. I could give it a go

The 1.6v and 1.8v variants run fine at 2.0v. Honestly the K6-2+s and III+s spec'd for lower voltages tend to overclock better than higher voltage variants with the same base clock speed.
That being said there is always some degree of luck involved. I have a 2.0v K6-III+ 450 running at 600mhz, but that is usually pretty rare and 550mhz is usually the stable limit for most.

My 450 is also a 2.0v chip and I've had it as high as 616 with no problem. But I know others on the forum have had issues getting them to clock past 550. Seems to be the average limit.

I haven't checked the price/availability in a while, but the k6-2+ 570 (at last check) was available on Ebay for a decent price, and those are relatively easy to mod into a K6-3+. That was how I finally got one that would reliably do 616 MHz. It's actually good for a bit beyond that, but if i try for a higher FSB on the motherboard I have the motherboard's cache has to be disabled, so there isn't a net gain in performance.

james1998hodges wrote on 2024-12-24, 03:55:

I want to find the fair price for the CPU as I can only find eBay listing for £200?

Maybe this is a late info for you, but you do not need to buy the fastest one K6-III+ CPU.
The most important thing for you to know, is:
regardless of the printed frequency on them in the range between 400 and 550 MHz - the most (90 %) 2+/III+ chips can overclock to 600 MHz.
If you are lucky, you can found one which can do 616 or 633 MHz (maybe 10 - 15 % of them). Faster than 633 MHz is possible for maybe 5 % of all CPUs.

About the Vcore: regardless of the printed value, nearby all "+"-versions can do up to 2,2-2,4 Volt. Some of them become unstable, if you go over 2,2-2,4 V. For those voltages in combination with frequencies >= 600 MHz you will need a big copper cooler with a very fast fan to cool them.
Personal for me, I will not go above 2,5 Volt Vcore (not even for test purpose).

Instead of a III+ you can buy a 2+ CPU and unlock it (more or less easy) to a III+, as shown here: https://www.hardwareluxx.de/index.php/news/ha … zum-k6-iii.html (in this link in German you only need to have a look on the red square inside of the picture). This unlocking is shown somewhere here on Vogons, too (sadly I lost the link). I have a few CPUs working pretty fine and stable under this condition 😉

And, you are absolutely right about the poor overclocking of non-plus-models -> if you really need overclocking, better you buy a notebook CPU (one with a "+").
By the way: like with the mainboard-jumpers, you can change the frequency of any "+"- CPU inside of Windows, using the software "CTU" (can be found on Phil's Computerlab here: https://www.philscomputerlab.com/k6-2-2-3-resources.html).