Changes

== CPC 6320 A 2022s RAM expansion - internal 320K for CPC 6128 straight from the mid 80s ==

The CPC Imagine it's spring 1987, you would have opened your favourite Amstrad magazine and a huge article says "320KB for your 6128 can - DIY - dk'tronics compatible". And then it explains that cost will be upgrade in the range of just £25 / 65DM / 220Fr / 4500Pts and that all you need is a soldering iron, 3 logic ICs, a few sockets and 8 RAM ICs - all of it probably available at your local electronics store. No special skills (besides soldering) and no special equipment required. I personally would have been fascinated and I know at least 3 people from my friends that would have instantly done that.  As we all know this never happened. RAM expansions were expensive, bulky, external pieces of hardware. The German magazine C'T published a DIY internal RAM expansion up to 320KB internally by 512K but you had to be able to program a PAL, needed to make your own PCB and it was not compatible with dk'tronics. All you could do is, write your own programs for it. You can guess how successful it was.  But: the idea that the C'T followed was brilliant. The 41256 RAM ICs that they used could replace the 4164 chips in the 6128 out of the box. Even RAM refresh for 8 address rows was already built into the CPCs architecture. Everything is basically there. All that is missing was logic that drives the additional address line A8. And unlike the C'T it needs to be done in an easy and compatible way.  And that, it turns out, is easier than expected: By replacing the 64Kbit ICs of the second RAM bank with 256Kbit ICs (41256) and the addition of a bit of 3 standard logic to drive ICs, the new address line A8 of these RAM ICscan be driven and a 6128 will become a 6320.  That would have been a dream in 1987.

Unlike many expansions from the 80s it's still possible - all required components can still be found easily. The logic ICs are standard ICs which most "makers" probably have lying around. If not you can find them in any electronics store or on Ebay for cheap. Even when you have to source the 41256 ICs it should be possible to build this for less than 30€. To be fair, for that price you can already get an external 512KB expansion - but if you don't like this external add-ons, want to build it with your own hands and stay true to the 80s era, this expansion is for you.