On Mar 7, 2011, at 12:56 PM, Zeke wrote: > I have an ancient 600 Mhz G3 iMac SE -- slot-load -- that I have been > using as an iTunes server for quite some time. (It was , also, just > fine for light web browsing.) Unfortunately, the CRT/power supply has > just gone kaput. > > For $40, I have been able to purchase a working 500 Mhz iMac but, > aside from a working CRT, I think it has a tic less performance across > the board. > > Is the extra speed worth me taking everything apart to create a true > Franken G3 or should I just pull the harddrive and 1G of RAM from the > first machine, put it all in the slower chassis, and call it good? > > At BEST I'm going to get a running 600 Mhz G3, with 1G of RAM, running > 10.4.11 and iTunes 9.2.1, which would be great with me. If the worst > isn't a noticeable difference...
There really isn't a very noticeable performance difference between a 500 and a 600 MHz G3 iMac doing things like e-mail and web browsing. But every little bit helps, of course. What you really want to make sure of, though, if you do try the swap, is that you're swapping an IBM 600 MHz logic board into an IBM 500 MHz chassis. Here's why. There were two different cpu manufacturers for G3 iMac 500 MHz logic boards: IBM and Motorola. The heat sink for the cpu is affixed to the bottom side of the perforated aluminum divider board, directly above the cpu of course. However, because of a difference in not only cpu size but also cpu logic board location, an IBM logic board will not mate properly with a Motorola heat sink, and vice versa. The penalty for a mismatch is a very fried cpu, very quickly, as I learned long ago. IBM was the only cpu used in 600 and 700 MHz G3 iMacs. So what you need to do, since the cpu is on the top side of the board, is remove the 500 MHz logic board and determine if the cpu is an IBM (which it will say right on the chip) or a Motorola, which you'll need 20-15 eyesight to see with your naked eye, or a magnifying glass. The Motorola chip is much smaller than the IBM. The IBM heat sink sits in a little recess in the divider board; the Motorola heat sink is a small rectangle of aluminum screwed/glued to the divider board. If your 500 MHz iMac is also an IBM machine, then the swap will be very easy. Remove the 600 MHz logic board with attached upconverter board and put it into the 500 MHz chassis. You might want to add just a teeny tiny bit of thermal paste on the heat sink to account for the compression of the thin thermal pad and the likely mismatch between the "new" cpu and its "new" heat sink. But if there's a mismatch between the 600 board and the 500 heat sink, all is not lost. You can really disassemble the two iMacs and transplant the 600 logic board AND 600 divider board into the 500 chassis. That will require discharging the two CRTs to avoid an unpleasant tingle. (OK guys, here's where you usually hijack this thread and rant on about whether the juice inside a CRT with a modern flyback transformer will kill you or not. Please don't.) I suggest you do some Googling for proper take-apart procedures, or find the appropriate Apple Service Manual, if you're going to disconnect the divider board with PAV attached from the iMac and discharge the CRT in the process. You have been warned. What I've done in situations like yours is to choose the best CRT (no burn-in, crisp focus, no scratches, etc.) AND its PAV (if working) and mate it with the best logic board, hard drive, optical drive and case plastics. I've sometimes had to swap the divider boards around to get an IBM/IBM or Motorola/Motorola match. One other point to consider: Not all 500 MHz G3 iMac logic boards came with 16 MB video chips. I've seen some with the 350-450 MHz 8 MB chips. If memory serves, somewhere along the way during the 500 MHz run Motorola boards switched from 8 MB to 16 MB. IIRC, all IBM G3 iMac logic boards had 16 MB VRAM. There's a big difference between the two if you're running OS X, which needs all the VRAM it can get in a G3 iMac. And one final point: There also were two different PAV boards. One does have a slide switch to select the appropriate CRT manufacturer (LG and CPT, IIRC); the other doesn't and will work with only one CRT brand. I'll bet you thought your idea would be simple to implement, right? Have fun, but do try to get an Apple Service Manual. Jim Scott -- You received this message because you are a member of the iMac Group, a group for those using Apple iMacs and eMacs. The list FAQ is at http://lowendmac.com/imac/list.shtml and our netiquette guide is at http://www.lowendmac.com/lists/netiquette.shtml To post to this group, send email to imaclist@googlegroups.com To leave this group, send email to imaclist+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/imaclist
