Apple1 RAMexpansioncard    Page No.:A15
       Last but not least i intended from the very beginning to also develop a RAMexpansioncard for the Apple-1 with as free as possible configuring options. there have been already some contributions published that described how owners of the original Apple-1 manipulated their mainboards to be populated with 4116 chips and then those boards had 20 kB RAM.   in fact there are different variations of possible RAMconfigurations and therefor it is upmost importent to also keep this card as variable as possible by offering wide range of adressing and allocating the different RAMbanks and offering to use different kinds of RAMchip population. The Mainboard offers either 4kB of RAMpopulation, 8kB or 20 kB. Depending to the availiable RAM on mainboard the expansion card should offer either 4 kB, 8 kB, 16 kB, 20 kB or 32 kB additional RAM and it should be possible to create entirely consistent RAMspace in one large block together.

The trouble started while examining the slot and the availiable signals at the slot. I discovered that a lot of requested signals for RAMtiming and RAMrefresh are not availiable at the slot and that signals needed to make that signals are not availiable too. From that moment i recognized that the development of a RAMexpansioncard would become a very tricky and difficult task. Its one thing to generate tha requested signals for refresh and row and column adressing  on the one side and its a complete other story to get that signals syncronized with the signals like the databus and adressbus as well as the CPU on the other side.


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