Re: Ultimax questions

From: Michał Pleban <>
Date: Sun, 20 Oct 2013 21:56:24 +0200
Message-ID: <>

Rob Clarke wrote:

> I have around 20 spare 27C020 2mb eproms which I was planning on using
> which would hold 32 x 8k images. With this method I would only fit 16
> images and as there's only 3 16k MAX cartridges, it's rather a waste.
> I'm wondering if there is a way of using /ROML to override the latched
> values on A16, A15 and A14 so all the $8000-$9FFFF images only use the
> bottom 4 x 8k images on the eprom?

Then I'm afraid you either need to use two EPROMs, or two latches. Two
EPROMs, one RAM and one latch will unfortunately not fit in a cartridge.
Two latches, RAM and EPROM - maybe, I haven't tried but it's still hard.
Unfortunately if you do not switch to a larger EPROM, you may be stuck
with 8 kB images.

> How about AND'ing pin 10, which is /IO2 on the 64 and /CIA on the MAX,
> with A7? On the assumption that none of the MAX ROM's don't write to any
> of the CIA's mirrored registers during their normal operation we could
> use a write to $DC80 and $DF80 on the MAX and 64 respectively?

/IO2 is not /CIA on the MAX, it's the CIA's shift register output.


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Received on 2013-10-20 20:01:10

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