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Upgrading a Dk'tronics RAM Expansion

296 bytes added, 19:57, 30 September 2020
/* Conversion to Silicon Disc */
The following is a description on how to convert a 64K [[Dk'tronics_memory_expansion|Dk'tronics Memory Expansion]] to 256Kand how to change its bank mapping to allow it to be used as a silicon disc.
== Warning / Disclaimer ==
As you can see, Dk'tronics were nice enough to use the same PCB for both the 64K and 256K version and even put the RAM and PAL ICs in sockets, but two ICs are missing in the bottom right corner.
 
== Parts List ==
The 74LS74 and 74LS153 are both widely available and very cheap because they are still in production. Although the 41256 isn't produced any more, they were used in many computers and other devices in the 80's and 90's and can be easily and cheaply found in many online auction sites.
 
 
== The Conversion ==
 
The first thing you need to do is carefully remove the 8 64K RAM ICs (Usually Part No. NMC3764N-15) and store them somewhere safe (you never know when you might need them).
The next thing we need to do is change the jumper settings. At the top right conner corner you will see two small vertical wire loops next to each other. These need to be removed and two new bridges added to connect the points horizontally as shown below.
Now you can re-assemble the device and test it using the Dk'tronics Banking Software found here: [[Dk'tronics_memory_expansion|Dk'tronics Memory Expansion]]or TFMs RAM check software found here: [[Media:4_MB_E-RAM_Test.zip]]
== Conversion to Silicon Disc ==
In the top left corner you will see two vertical rows of 5 holes (slightly obscured by a resistor). By connecting the top left hole to the bottom right hole, the expansion will then be mapped to banks 4 to 7. This will allow you to use the device as a Silicon disc or to connect two RAM expansions at the same time (only one should be set to banks 4 to 7). You can connect the two holes with a small piece of wire, for permanent conversion, or with a [[Dk%27tronics_Memory_Expansion_Gallery#256k_RAM_Silicon_Disc_for_CPC_464.2F664_-_modified_.28without_separate_ROM_cartridge.29|switch ]] so that the device can be switched back and forth between the two modes.
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