doc/3B1 Memory Map.ods

Fri, 18 Jan 2013 17:18:50 +0000

author
Philip Pemberton <philpem@philpem.me.uk>
date
Fri, 18 Jan 2013 17:18:50 +0000
changeset 129
8b24770dea79
parent 84
0d903718da81
permissions
-rw-r--r--

[memory] Emulate main memory read wrap-around

3B1s with 512K or 1MB of base memory have a decoding quirk which causes reads
to 'wrap around'. That is to say, on a 512K machine, reading from addresses 0,
512K, 1024K or 1536K will address the same RAM byte. On a 1MB machine,
addresses 0 and 1024K address the same RAM byte.

Emulating this incorrectly causes P4TEST to report an incorrect amount of
available base RAM.