Shared Projects by Waynetho

Requires one SN74LS158DR and one SN74LS32 (both narrow-body), one 33 ohm 1206 resistor, one 40 pin strip of turned machined pin header strip, cut into two 20 pin strips, one single-pin horizontal header for RA8 (J2), and one 40 pin socket.

Socket the PIA chip (6520) and right row of ramchips. Run a wire between all pin-1 pins on the right row of ram sockets and attach header plug (Dupont connector) for RA8 connection on module. Install 256k ramchips in sockets. Install module underneath PIA and attach RA8 wire from RAM socket pin-1. That’s it.

320K upgrade for 130XE (or 16-chip 65XE upgraded to 130XE). Resides under the PIA (6520) chip on the mainboard. One connection to extended DRAM pin-1, two-pin connection to SPST switch, to toggle between stock 128K with ANTIC bank support and 320K. (Memory MUX concept by Scott Peterson)

Assemble in the following order:

1. Install SMT parts

2. Install and solder 20-pin turned pin header strip on back of board for pins 1-20. You may want to use a socket or breadboard and both header strips while soldering to ensure alignment. Only solder pins 1-20.

3. Clip the pins short.

4. Install and solder 40-pin socket on top.

5. Install and solder second 20-pin header strip for pins 21-40 using same alignment method used previously.

6. Install and solder J2 and J3 horizontal headers.

NOTE: Do not use wide SMT ICs with NSR suffix. Use only narrow ICs such as SN74LS158DR and SN74LS157DR.

Installation:

1. Assemble board

2. Desolder eight xx64 DRAM chips (i.e., MT4164, M3764) on the right bank of RAM (extended).

3. Install and solder the eight 16-pin sockets where DRAM was removed

4. Using hookup wire, connect pin-1 of all eight DRAM sockets together.

5. Insert and solder new 41256 DRAM chips in sockets

6. Desolder the PIA chip, 6520 - take care not to damage the chip

7. Install and solder 40-pin socket in mainboard where PIA was removed

8. Install upgrade board in PIA socket

9. Install PIA into upgrade board

10. Connect single-pin Dupont wire to J2 and run to opposite side of board and solder to one of the Socket pins that you previously connected with the hookup wire.

11. Cut the 2-pin Dupont wire to about 4-5" and attach and solder the cut end to SPST switch

12. Plug 2-pin Dupont connector into J3

13. Mount SPST switch in suitable location in the 130XE case