Date   : Thu, 14 Feb 2008 19:24:24 +1100
From   : msmcdoug@... (Mark McDougall)
Subject: Model A (16K) RAM memory map?

Hi,

Could someone please explain the Model A RAM to me please?

According to MESS, the RAM $0000-$3FFF is mirrored at $4000-$7FFF?!? Is this 
the case from system startup, or is there some soft switch to configure it? 
Is it mirrored for *both* reads and writes? It must be at least for writes 
because booting in Mode 6, the MOS ROM is printing "BBC Computer" at address 
$6000+... but OTOH if it is mirrored for reads, then how does the ROM work 
out if it's a 16K or 32K machine?

Regards,

-- 
|              Mark McDougall                | "Electrical Engineers do it
|  <http://members.iinet.net.au/~msmcdoug>   |   with less resistance!"