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Old 10 August 2012, 13:55   #1
kipper2k
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A500 1mb upgrade chips available

Hi all,

I a,m able to get my hands on Fujitsu MB81c4256 20 pin DIP Ram chips. For those people that have a A500 Rev6 board or higher this means you can add an extra 512k directly to the motherboard to give you 1mb chip ram. I can buy in quantities of 100 which means that if at least 25 people are interested then i can order them. Feel free to add additional info in the thread if there are caveats etc
The cost per chip is $5.50, (my cost would be $4.53 + duties etc). You would need 4 chips to complete this mod and 4 sockets. Add your name to the list below if you are interested
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Old 10 August 2012, 15:04   #2
duga
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I would rather perform the motherboard modification to be able to use the trap door memory as chip ram. It seems to be easier for a solder novice and the trap door card gives me the benefit of RTC.
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Old 11 August 2012, 06:43   #3
TjLaZer
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Can this upgrade give you 1MB chip ram?
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Old 11 August 2012, 21:56   #4
prowler
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Hi Kipper,

I have sixteen KM44C256BP-8 chips which I bought from PowerPie5000 (IIRC) for upgrading A500 Rev6+ boards to 1MB chip RAM, but I suppose there must be more to it that just adding 4 chips in the vacant spaces, and so that's why the chips are still in the box in which I received them.

Also, I'm not sure that adding these chips doesn't prevent furher expansion via the trapdoor. Would you happen to have any further info on this upgrade, please?
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Old 11 August 2012, 23:49   #5
zipper
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I think the mobo empty sockets and trapdoor use the same address.
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Old 11 August 2012, 23:52   #6
prowler
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Quote:
Originally Posted by zipper View Post
I think the mobo empty sockets and trapdoor use the same address.
That's what I suspect.
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Old 12 August 2012, 15:57   #7
Jope
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No need to suspect anything, they are indeed the same RAM.

There is a schematic floating around where you can have 1MB chip on the motherboard and still have 512k ranger fast in the trapdoor, but people haven't had very good success with it.
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Old 13 August 2012, 20:05   #8
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Thanks for the info, Jope.
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