Name: Niko Hämäläinen
Title: Improving Reliability of NVRAM-module of Slot Machine’s 
Date: November 12, 2010 Number of pages: 43 p.
Department: Study Programme
Information Technology Software Engineering
Instructor: Auvo Häkkinen, Principal Lecturer
Supervisor: Jussi Lampiselkä, Game Platform Architect

The goal of this Bachelor’s thesis was to study the current implementation of the NVRAM
(Non-Volatile Random Access Memory) module of RAY’s (Raha-automaattiyhdistys, Finland’s Slot Machine Association) slot machine and to implement a new, more reliable one
as a replacement.
Currently the NVRAM module stores counter sets to physical NVRAMs and ensures that
no data is lost when the slot machine is shutdown. All data is written to two different
NVRAM-chips which are located on two different peripheral cards. Writing identical data to
two separate physical NVRAM-chips allows peripheral cards to be replaced without losing
any data stored in NVRAM.
The hardware used in RAY’s slot machines sets some challenges and limitations to the
functionality of the module. The existing module also sets strict requirements as the new
module should be able to replace the current module without making any changes to the
client modules.
The weaknesses of the current NVRAM-module were taken into account when designing
and implementing the new module. Unit testing and static analysis were brought to the development process from the very beginning of the project in order to improve the reliability of
the new module. The new module was also designed and implemented to be backwards
compatible with the current module.
The objective of this thesis was to implement a new, but a more reliable replacement for the
current NVRAM-module. Due to comprehensive testing, it is reasonable to expect that the
reliability of the new implementation has improved compared to the current one.
Keywords: NVRAM, Reliability, File Systems