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

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Date Posted: 13:09:58 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

Re: parts for chipping the LC575:

Obviously, you'll need a soldering iron. A good one to use if you can't afford a professional-quality Weller station is the Radio Shack 15W grounded iron, which retails for about US$8 here in the States. It has a blue handle in some stores but my two have grey handles. (Get two; using two makes it a lot easier to remove SMT resistors and such because you can put one on each and and just sorta lift the component off the board.) Make sure you get a grounded one whatever you do; you don't want static to fry a delicate component and ungrounded irons have had measured tip potentials in the +60V range (or so I've been told by reliable industry sources). 60V into a 5V part is a Bad Thing™...

Once you have a soldering iron (and the necessary skills to reliably operate it), you'll probably find yourself in need of solder. Silver solder is best. 60/40 solder is pretty darn good and is what Ratty Shack sells as its "electronics" solder. You basically want something designed for electronics and want to avoid acid-core solders as they can damage delicate components with their corrosive action.

You'll either need a full-size oscillator socket or a 14-pin DIP socket with all but the four corner pins removed, or if you're building a little board to hold everything, you can just use four individual sockets from a snappable row of SIP sockets.

You'll need a crystal oscillator, four-pin, full-size package, 5V input, in half the desired clock speed of the board. The board has some internal logic that doubles the clock frequency, so a 40MHz clock can be generated by a 20MHz crystal oscillator. 40MHz seems to be quite easily attainable; there are isolated reports of speeds up to 44MHz working well. 43MHz or so seems to be about the usual max for maintaining serial port function; if you don't intend to use the serial ports you may be able to go higher.

For the wire, I'd just use something small and stranded, probably about 20-gauge or 24-gauge (about the diameter of a wire in an IDC cable, like a SCSI cable).

Ratty Shack has small PCB boards that you can use to mount everything on, or you can just glue/velcro the oscillator somewhere convenient on the motherboard (like on top of the video chip/RAM controller).

Pretty much all of the above parts can be purchased from Digi-Key for no more than about $10 for a complete "kit" (excluding the soldering iron). If you want specific part numbers, e-mail me and I'll give you a list that I've put together. Keep in mind that Digi-Key charges a $6 or so service charge (on top of shipping) on orders under $25 so you should probably order enough to do two or three LC575s (or similar) at once. If you have other Macs you want to clock-chip, figure out what you need for those and put in the order all at once. (If you want to piggyback off the order I'm about to put in, feel free to let me know privately.)

If you're using a full 040 and intend to chip that, make sure you have a 33MHz version. I'm not sure how reliable the 25MHz units are past about 40MHz (they're rock-solid, for the most part, at 33MHz in my experience), although a lot of Centris 650s have run fine up to about 40MHz. (They originally had a 25MHz 040.) If you're using an LC040, you've probably got the original 33MHz chip in there and shouldn't have any problem getting it to at least 40MHz.

Digi-Key isn't the only online supplier but they're one of the biggest and they're very easy to deal with. Mouser Electronics is also pretty stocked, Newark has lots of stuff, Pioneer-Standard has a lot of interesting items, and I'm sure there are more. Of course, if you're lucky enough to have a local source (like the folks who live in SoCal/Silicon Valley often do) then you'll probably save enough by avoiding shipping costs that buying locally will be worth your while.

Good luck with it, and as I said, if you have any other questions, don't hesitate to get a hold of me privately.

cl

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Re: PowerCard 100 on a clock chipped LC575 logic board? -- Chris Lawson, 13:23:44 08/08/01 Wed