Re: PowerCard 100 on a clock chipped LC575 logic board? -- Welcome to the Colo(u)r Classic Forum

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Date Posted: 13:23:44 08/08/01 Wed
Author: Chris Lawson
Subject: Re: PowerCard 100 on a clock chipped LC575 logic board?
In reply to: Bruce (in Orlando) 's message, "Re: PowerCard 100 on a clock chipped LC575 logic board?" on 12:00:36 08/08/01 Wed

One more thing...the heatsink!

You'll definitely need a heatsink if you chip to 40MHz, especially with a full 040. There's a small problem with this, though: the CPU socket on the LC575 mobo doesn't have the usual heatsink clip mounts. (Since it shipped with an LC040, and the LC040 doesn't need a heatsink in most situations, Apple didn't bother using a socket with the mounts.) This prevents you from using the clip that comes with the heatsink on, say, a Quadra 650 or similar 040-powered Mac.

There are a couple options:

You can simply use gravity to hold a normal 040 heatsink in place. (Put some thermal/heatsink grease - also available at Ratty Shack of Digi-Key for a couple dollars - on the bottom of the heatsink, gently rub this onto the CPU, and you'll have a decent bond that will hold as long as you don't push it sideways with your fingers. If you don't move the Mac much, this will be quite sufficient.)

Or you can get a clip-on heatsink designed for a 486 that actually clips down onto the CPU in the little gap between the edge of the ceramic package and the CPU socket. This sort of heatsink may or may not have a fan with it; I recommend you get one with a fan (preferably one that piggybacks off the HD power cable) if possible.

Bear in mind, as I noted once before in this forum, that some 486 heatsinks have a small lip at either edge to hold them in place on the chip, which is slightly smaller than an 040 is. This lip will have to be machined off in order to use the heatsink effectively. If you'd like to go this route, search the forum for "heatsink" and you'll probably find my old post about where to get the heatsink-fan combos. If you don't have the necessary tools to machine off the lip, either find another source that has lipless heatsink-fan combos or contact me and we can arrange something at minimal premium to cover the 5 minutes or so it took me to remove the lip from one of my spares :) (Basically, I'd just ask that you cover the cost, shipping, and a couple bucks for my trouble.)

If you decide to find another source, make sure you call and speak with a tech support person or an engineer as most salespeople will probably have no clue what you mean when you ask if the heatsink is totally flat on the bottom. Oh, and if you find something, could you let us know where you got it? It would be worth a couple dollars or so premium to me to avoid machining in the future...

cl

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Replies:

Re: PowerCard 100 on a clock chipped LC575 logic board? -- Jeffrey G, 00:27:00 08/09/01 Thu

Clocked CC/575s -- Stuart Bell, 00:36:03 08/09/01 Thu

Re: Clocked CC/575s -- Chris Lawson, 04:53:42 08/09/01 Thu
Re: Clocked CC/575s -- Jeffrey G, 05:40:32 08/09/01 Thu