|
U8 provides the translation from logical page addresses (6-bits) to
physical page addresses (8-bits). There is a more detailed explanation of the mapping operation on each memory reference in the "4MEM User Manual" text file in the same directory as the schematic PDF. The 4MEM board has two uses: 1. To fill out SBC-188 memory above 512K; e.g., to 640K 2. To provide Expanded memory in 16K pages using EMM4MEM.SYS (in the SBC-188 folder). --John On 10/09/2012 05:44 PM, David Vincelli wrote: Memory on the 4MEM board, once the mapping in U8 is set up, operates at the same speed as memory on the SBC-188 board. Experimentally, the 80C188 clock rate is limited to 16Mhz when a 4MEM board is in use.Hi everyone, I'm trying to understand the 4MEM schematic and I'm wondering what the role of U8 (32K SRAM) is. Is it used for bursting a page byte by byte, cadenced with the clock? If so, does the EMS driver for the SBC-188 take advantage of this feature? --John |