Iisi 25Mhz Upgrade Faq

From: eepmatt@casbah.acns.nwu.edu (Matthew Friedman) Subject: The 25MHz IIsi Date: Sat, 27 Feb 93 0:49:16 CST Here's the FAQ sheet I compiled on the 25MHz upgrade for the IIsi. A couple of people requested that I send it to you for archiving in your reports section. -Matt Friedman eepmatt@casbah.acns.nwu.edu ----- FAQ: Upgrading your Mac IIsi from 20MHz to 25MHz Version 1.3 Compiled by Matt Friedman eepmatt@casbah.acns.nwu.edu 27 January 1993 ----- This FAQ was compiled from comments, letters, and posts to comp.sys.mac.hardware. I apologise for the many instances where I have not been able to include attributions and sources. Maybe in version 2.0.... :) ----- Contents: Q: What does the "upgrade" do? Q: What are the stats on the performance increase? Q: Why does the upgrade work? Q: Won't this void my warranty? Q: Where do I get what I need, and how much will it cost? Q: So how to I do it? Q: But my CPU's only rated at 20MHz. How can this work? Q: Why don't I just replace my CPU with one rated at 25MHz? Q: Can I go higher than 25MHz? Q: Do I need a certain speed of SIMMs for this to work? Q: What if I have a NuBus adapter or FPU? Q: What's the fail/success rate? Q: Why doesn't someone just check the speed ratings for all the chips? Q: Doesn't the upgrade produce more heat? Q: Are there any other drawbacks to the procedure? Q: What does Apple say about this? Q: Who should try the upgrade? Q: Don't you, as the compiler, want to include a disclaimer? ----- Q: What does the "upgrade" do? A: The upgrade involves swapping the 40MHz oscillator in your IIsi for a 50MHz one, thus increasing the CPU speed by 25%, from 20MHz to 25MHz. Some systems speeds, like displaying 8 bit graphics, have been noted to improve even more than 25%. All this for around $4.11. ----- Q: What are the stats on the performance increase? A: Numbers below are speed relative to a Mac classic, so bigger is better: BEFORE AFTER CPU 5.24 6.69 Graphics 6.17 7.64 Disk 1.30 1.34 Math 5.45 6.91 Overall Performance 4.75 5.92 (25% faster) KWhetstones 6.33 7.97 Dhrystones 5.11 6.62 Towers 4.42 5.69 Quicksort 5.01 6.43 Bubble Sort 5.88 7.50 Queens 5.83 7.33 Puzzle 5.61 7.22 Permute 5.33 6.55 Fast Fourier 4.27 5.39 F.P. Matrix 4.53 5.70 Int. Matrix 4.85 6.09 Sieve 6.53 8.35 BENCHMARK AVG. 5.31 6.74 Graphics: 1 bit (mono) 1.72 2.15 2 bit 1.83 2.31 4 bit 1.92 2.47 8 bit (256 colors) 1.22 1.89 (50% FASTER!!!!) Avg: 1.67 …