Hi @yock1960 !Hello new user here! I've been lurking on this forum for a few weeks now, after recently resurrecting a couple of vintage Macs that I used 20 or so years ago. After seeing the YouTube video by JDW on Spicy O'clock, I impulsively ordered one, without completely understanding all of the mods that would be required on my LC475, specifically the IC swap. I do see that there are MC88196DW80 available on eBay, but whether or not I could swap it out successfully is questionable at best. A question I have is, would leaving the MC88920 installed cause any damage or just make for a completely unsuccessful mod? As I watched JDW's video several times, I had already decided that ~42mhz would be my target and 40mhz would be better than the 33mhz I'm currently at, courtesy of a clip on gizmo purchased back in the day. This also as I do sometimes use a serial port joystick. I would assume that whatever course I may take, I would need to remove the clip on device...Correct?
Thanks!
First, I need to explain why the LC475 PLL clock driver should be replaced from MC88920 to MC88916DW.
Concept
MC88920:
This is originally for 12.5MHz input and 25MHz output. The upper limit of this clock driver is 19.5Mhz input and 39Mhz output. Also, depending on individual differences, it may reach up to 40MHz, but it is difficult for the clock to drop or stabilize over time.
MC88916DW80:
The PLL clock driver installed in the Quadra 840AV has the performance of 25Mhz input and 50Mhz output.
So, if it's 39Mhz or less, you don't have to replace it. Of course, the performance of Spicy O’Clock is up to 51Mhz, so it's a little wasteful.
This is my blog links:
LC475 restore and Overclocking
『Mac LC475 restore, PSU build and Overclocking』
*Jun 21, 2021 Added few schematics and descriptions. I recently repaired my fri…
ameblo.jp
Spicy O'Clock wiring diagramsの画像
ameblo.jp
MC88916DW80 Price - MC88916DW80 in stock - Buy MC88916DW80 on Utsource.net
Description: The MC88916DW80 is a single-chip, low-power, full-duplex, voice-band modem from Motorola. Features: Low power consumption Full-duplex operation Voi
www.utsource.net
Good luck!
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