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Old 27 March 2011, 00:38   #1
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Lightbulb A2091 14Mhz SCSI mod

Hello my fellow EAB'ers! As you probably know by now, I have developed a nasty habit of hacking my Amiga's with the intention of speeding them up in various ways.

So here is my implementation of the Official C= A2091 speedup mod. The reason I say "Official" is because it's mostly taken from the A2091 service manual. The really nice thing about this hack is that it's a very simple thing to do and a perfect DIY project!

First you need to make sure you have the WD33C93"A" (or the AMD "A" version) SCSI chip on the A2091.

Then following the service manual instructions you cut the trace for the upper 2 pins of JP201. Then you IGNORE the service manual instructions to jumper the lower 2 pins of JP201 and FOLLOW my instructions to jumper the outer 2 pins (Pins 1 & 3) and your SCSI chip should now happily be running from a 14 MHz clock!

I've tested this with C= V6.6 and V7.0 ROM's as well as Ralph Babel's Guru ROM. I recommend the C= 7.0 ROM's or Guru ROM for best performance. Using RSCP I've benchmarked transfers around 3.1 MB/sec on my A2000. Enjoy!

Note: See post #2 for info about the NEW 33C93A_Config tool. The actual transfer rates will vary depending on the speed of the hard drive, ROM's, CPU speed, Buster ZorroII vs. SuperBuster ZorroII and your choice of benchmark program!
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Last edited by SpeedGeek; 12 October 2020 at 22:42.
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Old 25 December 2012, 20:55   #2
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The 33C93A_14MHz util has been replaced by a new 33C93A_Config tool. Since you now have the option of using a 14MHz patched ROM or BindDrivers version you don't need to use an unreliable kludge to attempt to correct SCSI timings post boot.

All you need to do is verify the correct 33C93A Config settings for your CLK speed and this is exactly what the new tool does!

Last edited by SpeedGeek; 14 April 2014 at 22:31.
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