19 July 2009, 14:41 | #1 |
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using a 27C800 EPROM in an A600 for multiple KS
Hi All,
i am wondering about using a 1mb chip (27C800) in an A600 that contains 2 kickstarts, 1 in the upper and lower address area of the chip. I know the Xbox PLCC chips can be made to select high or low address areas for multiple OS's and wonder if the same can be achieved with a EPROM for the Amiga by holding an address line high etc. A one chip solution would be great with just a toggle switch. Can this be done ?, any ideas anyone ? Thanks heres the datasheet... http://www.datasheetcatalog.com/data...8/27C800.shtml |
19 July 2009, 14:52 | #2 |
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I think I saw someone on ebay selling just such a solution a month or so back. I can't see why it wouldn't work, since the advice for using a 27c800 with a single ROM is to hold the high address bit low, a switch to select low/high (Or some logic to do it from the keyboard at startup, a-la the more expensive kickstart switchers) should let you flip ROMs within a single chip.
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19 July 2009, 14:55 | #3 |
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It works, but because A600 supports >512K ROMs you must not connect "extra" address bit(s) to ROM socket.
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19 July 2009, 15:07 | #4 |
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Thanks guys,
What i would like to do would be to use 2.05 as the low area KS and 3.1 as the upper KS. I am assuming the process is to read my roms, and then byte swap them both, join the 2 images together with the 2.05 as the low address region, burn them to the 42 pin 27C800 and then this is where the guesswork comes into play... Is it Q15-A1 (pin 31) that controls whether the upper or lower region is read by either holding it high or low ? Thanks Last edited by kipper2k; 19 July 2009 at 15:34. |
19 July 2009, 15:08 | #5 |
Thalion Webshrine
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Once you have KS3.1 on an A600 you never ever want or need to go back to 2.05.
The only think you might want is KS1.3 for compatibility with patch for IDE support. http://www2.gup.jku.at/~tkoeck/kick1....device_patch/ |
19 July 2009, 15:15 | #6 |
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Thanks Alex,
One of the main reeasons is i want the option of the early startup to control whether its Pal or NTSC, i know some games dont like KS 3.1 so thats why i want to do it this way so i can leave my options open and also get the one chip solution working so i can play around with the different ROMs |
19 July 2009, 16:14 | #7 | ||
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Quote:
Quote:
You need KS1.3 for higher compatibility (which is why I mentioned it in my last post). Plus are you not going to be playing the WHDload versions instead? Last edited by alexh; 19 July 2009 at 16:21. |
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19 July 2009, 16:29 | #8 |
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Hi Alex,
I have a 4GB CF card and pcmcia card installed on my 1200 with the indivision so i am happy to use that with my WHDload. I just like to use the a500 and A600 sometimes with the good old floppy drive. Using a CF card with the OS installed i find a little too slow for use on the A600. Even just loading the A-Z games listing is slow lol. I like it though for the true retro (albeit with a few little modifications). Also a one chip mod iwould be better than a rom switcher in the sense that it would take up less room obviously in the A600 itself. Do you know which pin should be held high/low to address the upper/lower area of the chip thanks |
19 July 2009, 16:47 | #9 | |
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Quote:
Sounds like you are using a lame front end "game selector" tool. The "highest" address pin of course. Last edited by alexh; 19 July 2009 at 16:53. |
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19 July 2009, 16:51 | #10 |
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Thanks Alex
Its tough to use the A600 on CF card after you get spoilt seeing it behave on an A1200, i'll tone down the colours etc like you say and see what the results are. Thanks again |
27 July 2009, 01:02 | #11 | |
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Quote:
Thanks Last edited by kipper2k; 27 July 2009 at 01:37. |
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28 July 2009, 21:06 | #12 | |
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Quote:
The jump at the start of the first ROM image will make the CPU execute the code in the second image which is in the right address space (256KB ROMs are built with a base address of $FC0000) BTW, What did ROMsplit say about your 1.3 ROM image? Genuine 34.5 ROM images should work |
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29 July 2009, 02:52 | #13 | |
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Quote:
Thanks Doobrey, I should be getting the chips later on this week so i am waiting to get them before i sit down and play |
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