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Help needed to upgrade 400 to 48k


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Hi all,


I have a standard UK PAL 400 with 16k and I'd really like to upgrade to 48k. Sadly Best Electronics ran out of their upgrades a couple of years ago so I only have a few options left!


1. Is anyone selling an upgrade kit to the UK?


2. If not, then can anyone help me source the components and instructions I need? I'm not keen on the work/risk involved with the piggy back method but I've heard that, as I have a socketed board, I can simply replace the chips rather than solder on top of them.


I've seen this kit on ebay US... but sadly it's not available for shipping to the UK. Anyone know what the hidden components are and how I go about fitting them all?



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Been a looooong time since I did one of these but I think the pdf in the thread above may have been what I used. The factory kit was much easier.

Thanks, but that's the piggyback method I'm trying to avoid. According to the guy supplying the kit I've pictured you can simply pop the original chips out and replace, not piggyback solder on top of the original chips.


Here's the link to the kit. Says you replace chips, not piggyback. But sadly not available to me in the UK.



Edited by Mulbin
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They're just 4164 Ram chips as used by 800XL, early 130XE, breadbox C64 and plenty of other arcade machines and computers of the time.


Available from plenty of places. The more important thing is correct instructions as the 16K module and 400 motherboard are required to be modified. The Ram uses +5 Volts only and not the 12 and -5V the originals use. And some of the modification required relates to providing the ability for the 400 to actually see more than 32K of Ram.

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Guy on eBay is talking about not stacking of ram chips

only, same as the PDF does it. Can't avoid piggybacking

the two logic chips as there are no spots for two new

chips to go in. Same upgrade and eBay guys talk thru

their pants a lot. He did not re-create a new wheel

here, don't let his lazy talk confuse you - it's the

same upgrade. Just can't be any other way.


Be sure to read the entire thread SIO2 linked to.

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  • 2 weeks later...

There's also this 52K RAM card for the 400, all of the first batch are sold but there should be more made depending on demand.




Thanks for the heads up! I now have both of his cards installed - 48/52k card and his amazing s-video CPU card (wow, crystal sharp image now!). My 400 now thinks it's an 800!

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