Newsgroups: comp.sys.apple2 Path: news.uiowa.edu!chi-news.cic.net!ddsw1!news.mcs.net!nntp04.primenet.com!news.shkoo.com!nntp.primenet.com!news.cais.net!hunter.premier.net!news-res.gsl.net!news.gsl.net!news.mathworks.com!newsfeed.internetmci.com!newsreader.sprintlink.net!news.sprintlink.net!news-fw-22.sprintlink.net!howland.reston.ans.net!agate!dog.ee.lbl.gov!newshub.nosc.mil!newshub.cts.com!crash!pro-palmtree!rder From: rder@pro-palmtree.cts.com (Richard Der) Subject: FAQ-Zip GS upgrade: The 10MHz alternative Organization: The Palmtree BBS - 310/453-8726 - Santa Monica, CA Date: Sat, 3 Aug 96 10:54:53 PDT Message-ID: Lines: 134 Question: How fast can the Zip GS be pushed without getting new SRAMs or a new CPU? If I do need new parts, where can I find them at the lowest prices? Answer ------> You may be able to get it to run at up to 10MHz by just replacing the oscillator with a faster one for less than two dollars! I have a Zip GS that came as a 7/32 and was used at 7MHz for a long time. The board came with a socketed oscillator, so one day I swapped the 28MHz oscillator with a 36MHz one. The computer booted up at 9MHz. When the 36MHz osc was replaced with a 40MHz osc, the Zip ran at an amazing 10MHz! Your mileage may vary, though. The GS that this upgraded Zip resides has a high output power supply. Still, considering these oscillators cost $1.39 each, it is worth trying an oscillator swap alone first. If a faster oscillator alone won't do the trick, then a faster CPU and/or faster cache chips may be necessary. The following are sources for the parts (osc, CPU, and cache). ----------------------------------------- Here's what you need to upgrade to 10MHz: >From JDR Microdevices: Phone 1-800-538-5000 Fax 1-800-538-5005 BBS 1-408-494-1430 Web http://www.jdr.com Get a TTL Output Oscillator rated 4 times the speed you want the Zip to run. For example, if you want 8MHz, get a 32MHz osc. For 10MHz, use a 40MHz. You will actually probably need a 30MHz, a 32MHz, a 36MHz, and a 40Mhz oscillator: Part #'s: OSC30.0, OSC32.0, OSC36.0, and OSC40.0 because you want to test the Zip to see how fast it will go. It may top out below 10MHz. If it does, then you need a faster CPU and faster cache RAM if you want 10MHz or faster. --------------------------- You can get 64K's of fast cache from JDR Microdevices: Get 4 Static Cache RAM chips, Part #: HM62256LP-70 Price: $4.69 per chip (you need 4 of these for 64K) You can get a 14MHz fast CPU from: The Western Design Center (http://www.wdesignc.com) 2166 E. Brown Road (email: information@wdesignc.com) Mesa, AZ 85213 Part #: W65C816SPL-14 (for Zip GS or Transwarp GS accelerator cards for the Apple IIgs computer) Price: $19.80 + $4.00 shipping & handling (Western Design Center requires payment by Money Order) Once you get the cache chips and the CPU, remove the 4 (or 2) old cache chips and plug in the 4 new ones, making sure the orientation of the new chips is the same as the old ones were (you've just replaced slow 32K of cache with fast 64K cache). Remove the CPU chip and plug in the new CPU. Finally, experiment with different oscillators, replacing the original, and find the fastest one that works. DIP switch settings have to be changed when changing cache size. There are two banks of DIP switches on the Zip card. Switches 7 and 8 on DIP bank 1 determine the cache size. Bank 1 is the bank of DIP switches nearer the top of the card. The settings are as follows. size switch 7 switch 8 ------------------------------------------ 8K on on 16K on off 32K off on 64K off off With a faster cache and 14MHz CPU, you may be able to go above 10MHz by plugging in a 48MHz oscillator (for 12MHz Zip), or 64MHz oscillator (for 14MHz). Note: Even if you need a new cache and CPU in addition to a new oscillator, you can still upgrade a 7/32 to a 10/64 and beyond for around $40. If you are satisfied with 10MHz and are lucky and don't need the new cache and CPU, then you'd get a 10/32 upgrade for the price of a $1.39 oscillator! ----------------------------------------------------------------------- Good luck. (Note: The speed of these SRAMs will be sufficient to around 10MHz. The advantage of these particular chips are that they are available cheap and in the wide 600 mil package that the Zip sockets require. For 15MHz operation, even faster SRAMs may be required. Unfortunately, they are mostly available only in the skinny 300 mil packages. To use them, half sockets must be soldered into the Zip. They are also more expensive. Also consider that the performance advantage going from 10MHz to 15MHz is far less dramatic than from 7MHz to 10MHz. Factor in the risk of seriously damaging the Zip during soldering. Conclusion: the 10MHz operation is safer, requires no permanent modification of the Zip, and the chips of the right size are available and costs a lot less.) Please distribute this document freely. Apple II Forever. ----- The Palmtree BBS 310-453-8726 v.32 Inet: rder@pro-palmtree.cts.com