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Overclock LC475/P475/Q605 without soldering or spicy-o-clock
Posted by: stynx on 2026-01-21 12:33:57
No, because I‘m using SwitchRes to define profiles for automatic resolution switching for certain games.
I suppose then that I should do the resistor mod instead, since everthing works great at 40MHz
The resistor mod will only work for 33Mhz as far as i know.
Soft475 also changes the ram timings which might not be properly configured with only the resistor mod for 40MHz.
Posted by: croissantking on 2026-01-21 17:01:24
I recently picked up a couple of LC475 machines and tried out @Phipli's Control Strip Module – initially both topped out at 40MHz.
I upgraded one with a MC88916DW80 and it is now able to go faster. It's stable up to 45MHz, and crashes at 50MHz.

Configuration:
  • 68040FE25 (L88M mask) on a PGA adapter
  • MC88916DW80
  • 70ns internal RAM
  • 60ns RAM module
  • 80ns VRAM

Continuing my experiments with Soft475, I installed an 88916 onto my other LC475 logic board, intentionally picking one with a different/newer date code. Despite using the same L88M CPU as before, the results are a bit better: I can actually set 50MHz and it works. However, it is unstable. It runs for a few minutes, exhibiting graphical glitches (specifically font rendering, oddly) then crashes.
I will try adding more cooling to the CPU, and see if that helps.
Posted by: killvore on 2026-01-21 23:47:01
Can confirm that resistor swapping an LC475 to get 40MHz does not work, in my experience - it needs the more elaborate solution!
Posted by: croissantking on 2026-01-22 12:48:25
I will try adding more cooling to the CPU, and see if that helps.
This has helped. With a fan pointed at the heatsink, the CPU stays cool and runs stable @50MHz. Once I take the fan away, the heatsink gets hotter and hotter - and then the artifacts begin.
Posted by: croissantking on 2026-01-22 20:09:15
I tried my original LC475 board again. I had previously reported this:

It's stable up to 45MHz, and crashes at 50MHz.

It would hard lock immediately every time 50MHz was selected.

With a fan pointed at the CPU, it now works and runs without issue.

So it seems that both my boards will do 50MHz.
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