Re: is there any easy way to upgrade a C116 to 64k

Does that apply to the Plus/4 also?

Ted

On 5/1/2013 4:29 AM, Julian Perry wrote:
> I believe there are bus contention issues using expansion port memory expansions, due to insufficient decoding of the 16K RAM, mirroring it through the rest of address space.
> There have been previous discussions on this group on the matter, in 2012. This contention also pushed up power consumption, apparently.
> Considering how fragile TED machines traditionally are, I'm not wild on the idea.
>
> TBH, carefully done, the 16>64 upgrade is trivial - I made a nice bit of beer money in the late 80's doing just that. The two tracks that need to be isolated can be cut almost invisibly, and careful use of wirewrap wire to bring the two additional address lines to the multiplexor can be done very tidily (and on the underside of the board.) Just make sure the 64kx4 chips you use only require 7 or 8bit refresh.
>
> Callan
>
>
> Hello Imre,
>
> Wednesday, May 1, 2013, 6:06:45 PM, you wrote:
>
>> You can use external expansion like this one:
>> http://plus4world.powweb.com/hardware/16_To_64. There are several
>> types of them in the hardware section of Plus/4 World.
>>   But this means you can't use your expansion port for anything else
>> (except the 1551 drives which has a pass-through connector).
>
>
>> 2013/4/30 Gerrit Heitsch <gerrit@laosinh.s.bawue.de>
>>   
>> On 04/30/2013 09:44 PM, didier@aida.org wrote:
>>    
>>   is there any easy way to upgrade a C116 to 64k ?
>>   
>>   I found a few document on the web…
>>   
>>   To upgrade a C16 to 64k
>>   
>>   Looks like awful hack L
>>   
>>   With tracks cuts and A lot of spaghetti to rebuild the tracks
>>   
>>   I mean upgrading without mutilating the mother board..
>>   
>>   
>>   There is no other way than to replace the existing RAM with 41464
>> DRAMs. In order to use them properly, you will have to cut 2 traces and make 2 new connections.
>>   
>>   But you're lucky insofar that it's way easier on the C116 than on the C16.
>>   
>>   Short form:
>>   
>>   - Replace the 2 RAMs with 41464 (64Kx4) DRAM
>>   - Cut trace between pin 14 and Pin 16 of U8 (topside)
>>   - Cut trace between pin 16 and Pin 2 of U7 (underside)
>>   - Make a new connection between CPU Pin 22 and U7 Pin 2
>>   - Make a new connection between CPU Pin 21 and U8 Pin 14
>>   
>>   Done... Now you should be greeted with 60671 Bytes free.
>>   
>>   U7 and U8 are the two 74LS257.
>>   
>>    Gerrit
>>   
>>   
>>   
>>   
>>   
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>>   
>
>
>


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