Re: GEOS cartridge

That sounds cool, can you provide High quality pics of the PCB and 
ROM dumps of the two
27256 EPROMS?

Thanks


>Hallo allemaal,
>
>
>I just found the GEOS cartridge I mentioned a week or so ago. It
>has 'only' five parts:
>- a switch between EXROM and GND to en/disable the cart
>- two 27C256 EPROMs
>- one unknown 14 pins IC
>- one unknown 16 pins IC
>
>Unfortunately the codes of the two ICs have been removed :( But I'm
>quite sure that the 16 pins one is a 74175. The problem: my IC
>tester says it's not. But I just had the idea to test this by
>replacing it with a marked one. (not now, tomorrow)
>
>The 14 pins one gives me head aches:
>
>
>                     +------+
>           +----- 2 -+      |            +------+
>PHI2 -----+         |  ??  +- 1 ---- 5 -+      |
>           +----- 3 -+      |            |  ??  +- 4 --- 9 of 175
>                     +------+     +-- 6 -+      |
>                                  |      +------+
>IO1 -----------------------------+
>
>Pins 8..13 are not used.
>
>
>There aren't many ICs with outputs at pin 1 and 4. What immediately
>came to my mind was the 7402. But pin 9 of the 175 has a rising
>edge. OTOH, at the falling edge of IO1 the address should be valid
>as well and that could work. But again the same problem: my IC
>tester says it's not. We'll see tomorrow.
>
>But it could be that one of you know of ICs that I don't know and
>still fit the description.
>
>
>--
>
>Kind regards / Met vriendelijke groet, Ruud Baltissen
>www.Baltissen.org
>
>
>
>
>
>
>
>        Message was sent through the cbm-hackers mailing list

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