Date   : Thu, 14 Feb 2008 11:13:52 +0000 (GMT)
From   : chris@... (Chris Johns)
Subject: Model A (16K) RAM memory map?

On Thu, 14 Feb 2008, Mark McDougall wrote:

> 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?

There is a link inside the machine that sets if the machine is 16k or 32k, 
so the MOS could use this to determine the memory size.
-- 
  Chris Johns <chris@...             >