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Lasagna fan and cooling requirements of various CPUs
Just what will a Lasagna fan handle?

New MessageLasagna fan and cooling requirements of various CPUs (modified 0 times) gramster
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Hi all

I have a v4-ish i-Opener (doesn't seem quite a v4 but did come with a Rise CPU). I am planning to put in a K6-3+ at 400MHz once I figure out the necessary mods (the standard v4 directions don't quite apply, and there is no SW4). In the meantime I wanted to get WinXP running, and WinXP setup won't work with Rise CPU. So I got a 2.8v 200MHz Pentium MMX chip and dropped that in. I have a Lasagna fan installed as well.

The IO runs for about 30 or so minutes and then starts rebooting (or occasionally just freezing). I've eliminated memory as the cause (tried different 128Mb and 256Mb Sendo sticks, which pass MemCheck86 in a laptop). If I put the Rise processor back in things seem to work fine (with FreeBSD doing a "make world"). I've tried a P166 overclocked as well, and it also does the rebooting. Because FreeBSD runs fine with the Rise chip, and I know the Pentium chips work in desktop machines, I can only conclude that they are overheating.

So my question is: has anyone else experienced this? Just how capable is a Lasagna fan of cooling? It sounds like everyone seems to use them, but I'm starting to lose confidence that it will work for cooling the AMD chip.

BTW I have the RF shield removed and even cut a 2" square hole out of the plastic case to make sure air flow was not an issue.

02-07-2003 11:21:10

New MessageRE:Lasagna fan and cooling requirements of various CPUs (modified 0 times) vailr
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I'm running a K6-III+ 450 underclocked to 300 MHz at 1.6 volts, with a CPU cooling Tennmax fan in place of the original large aluminum heatsink. The RF shield is in place, with a small opening cut directly above the CPU, where the plastic cover vent holes are located. I'd suggest running Motherboard Monitor to double-check that your voltages are correct. Someone else suggested removing the AMD heat spreader on their K6-II+ CPU for better air flow, but I haven't attempted that. Once you do the soldering for the voltage reduction for a K6-II or III, the CPU should run cooler. Also, your freeze-up problem could still be a memory incompatability problem.
02-07-2003 12:49:36

New MessageRE:Lasagna fan and cooling requirements of various CPUs (modified 0 times) gramster
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I cut the hole in the plastic case because I found the Lasagna fan was very noisy otherwise.

I don't believe memory is my problem, as the freezing/rebooting does not happen when the Rise CPU is installed. The 256Mb Sendo memory was recommended on this BBS as good for IO's so it shouldn't be a compatibility issue.

I'm probably going to try mount a bigger heatsink and fan (now that I have the hole in the plastic case so it can protrude) and will report the results I get with that.

02-07-2003 14:55:22

New MessageRE:Lasagna fan and cooling requirements of various CPUs (modified 0 times) jimmy
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I have modified 8 i-openers to use AMD K6-2+ and K6-3+ chips running at 400 MHz using Lasagna fans and the slim line laptop fans sold on eBay. I have had no heat problems with most of the units. I find the Lasagna fan cools better than the slim line fan, but I have had no identifiable heat related crashes with either fan type. The exception was with one particular K6-3+ that just plain ran hot, so you take some chance getting a poor CPU. The Lasagna fan is very noisy if you don't cut away the RF shield AND the pastic case in the area over the fan. The slim line fan is pretty quiet with just cutting the RF shield, and this lets you have a (slightly) prettier unit (but whoever said the i-opener is pretty besides me?).

P.S. Three of the 8 units with both fan types represented have been running for over a year now without any complaints from their users. These machines are used every day for email and web surfing.

P.P.S. The Badflash deep back case gives you enough room to have really quiet Lasagna fan performance. The case is a heat trap, however, and requires that some strategic holes be cut (or chassis punched) in the the side plates to get proper cool air flow to the fan and to let hot air out.

02-07-2003 19:38:01

New MessageRE:Lasagna fan and cooling requirements of various CPUs (modified 0 times) gramster
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Yeah, I'm beginning to think the P200MMX might just be a bad apple (and the P166 might just be intolerant of overclocking). I hope so anyway, as the Lasagna fan set me back about $26. Unfortunately, my local PC recycle store has no more P200 CPUs (although they have a bin full of discarded P166's so I may just try overclocking a different one).

If I learn any more, up to and including getting the AMD chip in, I'll follow up.

02-07-2003 22:25:41

New MessageRE:Lasagna fan and cooling requirements of various CPUs (modified 0 times) BadFlash
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This sounds like a power supply/votlage issue. Be sure your power supply is putting out the correct voltages. Intel chips are quite intollerant to this. AMD only a little more so.
02-08-2003 09:07:20

New MessageRE:Lasagna fan and cooling requirements of various CPUs (modified 0 times) mp3boombox
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gramster Do you have a DC-DC voltage mod? and you do have the dual voltage hack in place by moving the 2 big resisters???? If you do not have a dc-dc power adapter your chances of getting a p200mmx working are NILL. Even still they pump out a lot of heat. The moble K2+'s are the best bang for your buck. I got my k6-3+ 450mhz for $50 about ? a year or 2 ago. It over clocks to 600mhz just fine using a deep back case from badflash and piping the hot air right out of the case.
http://members.panax.com/bachh/ My EZnet 200 tower, hacking page.
02-09-2003 11:50:44

New MessageRE:Lasagna fan and cooling requirements of various CPUs (modified 0 times) gramster
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This is a v3b/v4a - which means it doesn't have the voltage DIP switches but does have the split voltage (AFAIK). The Rise CPU and the P200MMX are both 2.8v core.

I do think its a heat issue. Over the weekend I added SW1, and dropped the multiplier to run the P166 without overclocking. That has given me better results, with the machine running now from a cold start for up to two hours before going flaky (but it does still go flaky eventually).

I'm still waiting for my AMD K6-3+ 400MHz chip to arrive; it will be interesting to see how it behave once I have that.

02-10-2003 14:35:30

New MessageRE:Lasagna fan and cooling requirements of various CPUs (modified 0 times) gramster
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Got the K6-III+, and made all the mods to run it. At 400MHz the machine freezes up very quickly. At 300MHz it stays up overnight (the longest I've tested it). I'm going to have to experiment with other cooling solutions, or else go for K6-2+.
03-08-2003 19:24:52

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