Irem I-IM mirroring config

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FrankWDoom
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Joined: Mon Jan 23, 2012 11:27 pm

Irem I-IM mirroring config

Post by FrankWDoom »

Where nes boards have bridge spots marked h and v mirroring, this board has a10, a11, and a12 (top center)

A11 is the default, giving horizontal mirror. A10 should be vert if i understand correctly. What would a12 do?

This is mashou (deadly towers), mapper 34 for reference.
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lidnariq
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Re: Irem I-IM mirroring config

Post by lidnariq »

It'd be fixed one-screen. The other 1KB would still be usable as scratch RAM at PPU address $3000-$33FF, but that's hard enough to get at that there's no real utility in using A12 instead of ground.

I'm pretty amused to see a contemporary instance of "putting an LED on a cart so that it glows".
FrankWDoom
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Re: Irem I-IM mirroring config

Post by FrankWDoom »

Its interesting it was designed with that flexibility given there is only one title released on it. One screen is fairly uncommon anyway isnt it?

the led is a neat feature. This cart is going to be turned into project blue- itd be neat if i could find a blue led to replace it. Can you buy leds molded like this?
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lidnariq
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Re: Irem I-IM mirroring config

Post by lidnariq »

The only game that I remember having been released with hard-wired one-screen mirroring is Irem's Major League. I'm hard-pressed to think of many situations where it's more useful than horizontal mirroring.

I know I got bargain bucket LED assortments from Radio Shack a few times containing some with that fresnel lens on the front, but I haven't seen that specific form factor in years. Closest thing I can find is digikey:OVLLB8C7
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Memblers
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Re: Irem I-IM mirroring config

Post by Memblers »

You might be able to find a panel-mount lens that's a close enough fit, break off the snap-in tabs (if needed to lower the height) and glue the LED into it.
https://www.digikey.com/products/en/opt ... lenses/112
FrankWDoom
Posts: 260
Joined: Mon Jan 23, 2012 11:27 pm

Re: Irem I-IM mirroring config

Post by FrankWDoom »

Thanks for the tip. At this point I'm leaning towards leaving the red one for simplicity.

Another interesting thing i just noticed- there are 4 more bridge points the the lower right of the a12 bridge. They are unlabeled but they are set up in pairs for prg rom holes 2 and 24, controlling whether each is connected to a16 or gnd. It looks like toggling each pad would allow a 27c010 to drop in directly. Im going yo give a shot.

Prg pins 30 and 31 are tied to 5v and the 161 outputs for those are NC so they'll still have to be jumped.
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