For sale is our new Ohio Scientific Universal RAM board, the GW-OSI-RAM1. This board supports up to 128 KW of memory (with memory management) and 8 or 12 bit word length. 12 bit word length is provided so that the board will work with the OSI 560Z "Processor Lab," which includes PDP-8 software compatibility.

This board is a prototype of our new design, but is fully functional and completely tested. The prototype differs from the production board in a few minor ways, the only significant difference being that it lacks a corner mounting hole. There are no circuit traces in this area, so a hole can be drilled for mounting, if desired.

The GW-OSI-RAM1 is designed to coexist with any memory that may already be present in your Ohio Scientific system. RAM can be enabled in 4K blocks, anywhere in address space. For example, if you have a system with a 500 board that has 4K onboard, simply set the switch for the first 4K to OFF. Most systems will require the upper 16K to be disabled, in order to avoid conflicts with I/O devices. The two 4K pages from 0xD000 - 0xE000 can be enabled for CP/M support with the OSI 510 triple processor board. It's also possible to overlay RAM and ROM in the same address space, so ROM BASIC can be installed on the GW-OSI-RAM1 and used with CPU boards that do no have enough ROM space for BASIC.

Features as follows:

• 128 KW total memory capacity
• Full 64 KB expansion for most standard OSI systems
• 12-bit word compatibility for use with the OSI 560Z "Processor Lab" in PDP-8 mode
• Lamp register mezzanine connector
• Prototype area
• Fully buffered address and data busses
• Uses all standard TTL and CMOS parts, no hard-to-find vintage ICs
• High quality FR4 board, full thickness for improved rigidity over standard OSI boards
• Low power, will not strain small OSI systems' power supplies

This board has been extensively tested throughout its development process, here are some links to more information on its design and development:

• http://www.glitchwrks.com/2017/05/03/gw-osi-ram1-universal-ram Information on the development of this prototype
• http://www.glitchwrks.com/2016/04/23/32k-ram-for-osi Information on the first 32K prototype built
• http://www.glitchwrks.com/2016/05/17/64k-ram-for-osi Expanding the original prototype to 64K
• http://www.glitchwrks.com/2017/02/26/osi-560z-build Information on the OSI 560Z, including designing the 12-bit portion and lamp register

A preliminary manual is available as well:

ftp://filedump.glitchwrks.com/manuals/glitchworks/gw-osi-ram1/gw-osi-ram1_manual.pdf

This auction includes the GW-OSI-RAM1 board, populated with two 62256 SRAMs, which can be used to provide 32 KW of 12-bit memory or 64 KB of 8-bit memory. The memory management section is populated but not jumpered in, since most Ohio Scientific systems do not use memory management.

If you have any questions about system compatibility, or would like the board shipped with a particular configuration, please contact us!