Want to upgrade 64k to 128k

[MacDeath]

A little question here.


Many classic Ram expansion came in 2 variant if I remember correctly...
those for 464/664/X64... an,d those for 6128...


The thing was (if I remember well) that a simple +64K (dk tronic or dobbertin ? both) put on a 6128 would not work as it simply take place of the existing +64k RAM on the motherboard...

As a result you need a more than +64K only expansion to actuazlly improve the RAM...


Can someone explain me better ? Is there a way to still get the existing+64K on board usable ?

[steve]

The dk'tronics ram disabled the second internal 64k in a 6128, so if you use a 256k rampack you get 320k memory available on a 6128, I do not know if it is the same for other memory expansions and I do not know if there is any way to reactivate the second 64k bank.

[TFM]

There are several RAM expansion ideas being contemplated at the moment. But that brings me to a question that maybe someone here can answer: Some RAM expansions have been described as 100% DKTronics compatible and others (Inicron I believe) are described as not fully DKTronics compatible. My question is, what makes them only "almost compatible", and what's the definition of 100% DKTronics compatible.

Bryce.

Boiled down:

Half way compatible means banking of 16 KB blocks to &4000-&7FFF by using: &C4..&C7 and &CC..&CF (and the same for &D4... , &E4...., &F4....).
Further banking/switching of whole 64 KB blocks


100% compatible in addition means to support configurations &C1 and &C3. This is important for banking a 16 KB block to &C000 - and in the same time to move the screen from &C000 to &4000. Actually that logic is part of a PAL in the 6128. Therefore 464/664 can (natively) not run CP/M Plus (or SOS or FutureOS).

However some RAM expansions like the 512 KB from Dobbertin can cope with that problem and allow CP/M Plus on 464 / 664.

I tried to keep is short for the beginning.

[TFM]

The dk'tronics ram disabled the second internal 64k in a 6128, so if you use a 256k rampack you get 320k memory available on a 6128, I do not know if it is the same for other memory expansions and I do not know if there is any way to reactivate the second 64k bank.

The Inicron RAM expansion has a switich for that 64 KB. And this makes sense, since the Inicron 512 KB is battery buffered SRAM.

But you can't use both 64 KB blocks at the same time.

[TFM]

Now how to use more than 512 KB RAM?

Well, by using port &7Fxx you can manage 512 KB in a compatible way.

Now you can use ports &7Fxx, &7Exx, &7Dxx, &7Cxx, &7Bxx, &7Axx, &79xx and &78xx to manage 512 KB each. And 8 * 512 KB makes 4 MB. I do not suggest to use ports &77xx... &70xx though.