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Delta Products 64K Dynamic RAM Board

It was the probably Delta's most sophisticated board.

Delta 64K RAM

The board utilized (Cromemco style) bank select capability (IO port 40H) to allow up to 8 boards to reside in a system. The board is configured as four 16 K blocks, one or more of which can be inactive for any or all boards in a system. This allowed easy implementation of CPM+. The D.P. computer BIOS allowed you to use bank 0 for main ROM and banks 1-15 for a RAM disk.  A system running with 2 double sided 8" floppies plus a four board RAM disk was super fast if you moved your programs and data to RAM vs. leaving them on the floppy.

BTW, the BIOS had a few quirks and didn't match the print out that came with the documentation. As supplied the handshake failed for anything above 9600. It was a simple matter of changing the handshake overflow test code to test all pins of handshake serial lines.   The format used on the 8" floppy disks was always single density for the first track and then could be either single to double density for the remaining tracks. This made swapping with other computers only possible if you formatted and stored data in single density.


Many if not all of these Delta Products 64K memory boards also had a common of having the tantalum capacitor for the minus power voltage installed with the + & - leads reversed and so marked on the board too.  After a period of time the capacitor would from being install wrong short out the minus power supply and the board would die. Replacing the capacitor with a new one and having the + lead going to ground and the - lead going to the minus power would get the board working again.



The manual and schematic for this board can be obtained here.


Other Delta Products S-100 Boards
Z80 CPU Board    FDC Board   64K Dynamic RAM Board


This page was last modified on 10/31/2014