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In a few short years memory boards at Cromemco had come a long way from their initial 4K RAM board.  The 256K-Z was essentially the last RAM board the (US) company made.

Cromemco 256K DRAM

It had all the things learned from the previous boards. The 256KZ could automatically switch from contiguous memory addressing when used with the Cromemco DPU based 68000 board to bank selected memory when using a Z80 system.  Switch settings on the board determine the address range for the  68000 memory space. The custom PROM plugged into the IC39 socket determines the memory banks selected in Z-80 systems. This means that with Cromemco's dual processor D-series systems you could use either the Z-80 or 68000 Cromix Operating System interchangeably, without changing any  settings  on  the 256KZ  memory  board.  If the custom PROM was removed the board operated in just the 68000 mode. The 256KZ was byte-addressable or word-addresseable. During Z-80 memory operations eight bits of data are transferred at one time, while with 68000 memory operations, 16 bits of data are transferred at one time. In this way/ there is no speed degradation when using the  256KZ with a  68000 board.
The manual for the board can be obtained here.


Other Cromemco S-100 Boards
ZPU  SBC   4KRAM  16K RAM  64KZ RAM  64KZ-II RAM  256KRAM  8KBytesaver  Bytesaver-II  
16KPROM  32K Bytesaver  4FDC   16FDC  64FDC  WDI  WDI-II   STDC   DPU
4PIO   8PIO   TU-ART  D+7A I/O   Dazzler  PRI   GPIB Board   XMU  XXU  Other Boards


This page was last modified on 10/25/2013