My 500 did about 560 or so. I wouldn't say that Katmai are great overclockers, the L2 cache is the limiting factor. If you up the FSB in small steps like usual you should be safe, because usually the system won't even boot before the SRAMs release their magic smoke.

Disclaimer: I can't be made responsible if you fry your $15 CPU 😉

I have a Katmai 600, the one they withdraw soon after release (but not recalled as the 1133 coppermine was) in my support box that I use to prepare bios update disks and the like.
Its rock stable at 600 mhz but wont even overclock to 620 mhz without issues, The louse overclocking could be related to the fact that I use a MSI MS6119 OEM BX board crossflashed with the normal MS6119 bios.
I would aim for 4.5*133 and if that fail settle for 4.5*124. If it needs more voltage give it more voltage, its not easy to kill a Katmai. Up to 2.3v or so should be safe as long as it dosnt get to hot.

Katmai 450 @ 600:

Darkman wrote:

... would it be safe to up the FSB (multiplier is locked of course) when the CPU is using just a stock heatsink and fan.

Got a pic of that?

TELVM wrote:

Katmai 450 @ 600:

Darkman wrote:

... would it be safe to up the FSB (multiplier is locked of course) when the CPU is using just a stock heatsink and fan.

Got a pic of that?

well , its not exactly the same, but the CPU it looks pretty much like this one,

its what the CPU itself came with , and it honestly looked like it wasn't taken out of the box (which it came with)

there is also of course the concern regarding what raising the FSB will do to the Voodoo 3 Ive got in the AGP slot

btw the 15 dollars wasn't just for the CPU , it was the combined price of the motherboard , CPU and a stick of RAM , and half of that price was shipping.

I also managed to oc my Katmai to 600 from first try,the problem in my case it's the videocard,it doesn't like the overclocked agp.

Supposed both the Katmai and the Voodoo like 133MHz we'd be talking ~45W TDP. I'd put at least an 80mm fan at the rear panel extracting (even better if we cut off the grill to unchoke the fan). Then if the case left panel allows another 80 intake pushing directly ontop the CPU would be heaven, otherwise at the front.

That one in your pic isn't precisely the best heatsink that came OEM with Slot-1 P-IIIs, these worked better:

I'd see if I can scrounge and transplant one of these. With decent case ventilation these can go passive (old toy fans don't move any air at all anyway).

well, I overclocked it , but not to the full 600mhz, this motherboard has the options for 100 , 112 , 133Mhz, (in addition to 66), so I tried the 112Mhz FSB option , which means the CPU is clocked at 500Mhz

I ran 3DMark2001, as well as System Shock 2 and UT99 for about an hour and a half, it seems to be very stable.

the problem is that I have no idea what the CPU temperature is, the better heatsink advice is of course sensible, though for the price of the heatsink I can get an actual 600mhz Katmai, which kind of defeats the purpose of it.

Honestly, I don't think knowing the exact temperature really matters... those things were pretty tolerant of heat. If it runs stable, and the heatsink doesn't burn your fingers when you touch it, you should be alright.

I run my Katmai 550 stable at 616 MHz (112 FSB). I can set it to 732 (133 FSB) in DOS without any problems (in Windows it won't boot, probably because the AGP card can't keep up at 90MHz.)

Last week I upgraded the heatsink:

Temperatures dropped from 42°C to 36°C on full load...

Sometimes Intel would use cache chips of a higher rated speed than necessary. SL35D was one of these situations.

swaaye wrote:

Sometimes Intel would use cache chips of a higher rated speed than necessary. SL35D was one of these situations.

What a shame to have an SL35D (PIII-450) and not be able to test it at 4.5x133=600MHz because of lack of mobo... 😊

a little update on the situation , I thought of the heatsink advice and ended up finding a CPU and heatsink , its a proper 600mhz Katmai, so its the most this motherboard will take, and it seems (judging by the sticker on it) that it was part of an IBM Netfinity , which Im not sure what that is exactly (Im assuming a server of some kind?, though what would a Katmai be doing in a server?). so no need for overclocking

450Mhz on the right (with the fan taken off) 600mhz on the left, only annoyance here is that I can't seem to fit any fan on this bigger heatsink , the tabs are a rather odd shape, I did run 3Dmark2000/2001SE and it was stable, though Im not too confident about the lack of a fan.

No real need of CPU fan with that type of heatsink ontop a Katmai 600, you can let it go passive. What you need is a case fan extracting at rear panel, and another intake fan at left panel (if possible) or at front panel, for decent case ventilation. The larger the fans the better.

sadly there isn't any space for a rear fan , there is a decent fan at the front of the case as well as plenty of vents on the back, but no space overall .

the case is quite large, but built in a way that putting on extra fans is almost impossible without drilling holes in the case or something of that nature.

Dang, that's the problem with many ancient cases, terrible case ventilation 😵 . At least the PSU sucks air from inside the case close to the CPU? Pics of case internals would be interesting.

there you go, you will have to excuse the cable mess, not much one can do in these cases.

Darkman wrote:

there you go, you will have to excuse the cable mess, not much one can do in these cases.

You can always throw money at that problem! 🤣

http://www.newegg.com/Product/Product.aspx?It … N82E16812200109

http://www.newegg.com/Product/Product.aspx?It … N82E16812200310

The rear panel of that case is hopeless for ventilation, but if I understand your PSU correctly and it only sucks air thru the slots on its "underside", right over the CPU, at least the cooling path for the CPU is sound:

Some easy and cheap extra touches you can do to improve your cooling:

1) Clear the "path" painted above of wiring as best as you can, specially the flat wide IDE cables which are poison for airflow.

2) Seal with duct tape or something all the slots in the rear panel. This sounds counterintuitively negative for cooling, bull all those slots do is recirculate warm air expelled backwards by the PSU fan in an "air short-circuit".

3) Unplug the comp from the wall and cut off the grill behind the PSU fan. This can be done with cutting pliers and a bit of care without removing or opening the PSU.

4) Cut off those three horizontal plastic bars behind the fron intake fan. If by now you are trigger-happy with the cutting pliers, also cut off the metal grill in front of the front intake fan.

Grills are poison for airflow and they need to be destroyed.

So, how much air circulation does a 120mm fan lose from having a grill in front of it? I'd like to know since I have a Cooler Master Storm Scout case, and I'm thinking of possibly dremeling out the fan grills.