----- Original Message:
Date: Thu, 05 Jan 2012 10:10:08 -0500
From: "Bill Sudbrink" <wh.sudbrink at verizon.net>
James Attfield wrote:
> FYI the ROM on the 'FDC flips in and out the entire top 32K bank.
I just double checked the schematics and this is not
correct.
The 16FDC feeds address lines 15-12 through a 74ls30 to do a
specific decode for a 4K address range, normally set to $C000-$CFFF.
If the high four address bits do not match, the card will not
respond.
Bill S.
--------------------------------------------------
The 16FDC does indeed have a set of jumpers to select a 4kB block, normally
at $C000, but the 64FDC that we were talking about only uses A15, i.e. the
upper 32kB; also, the 64FDC's RDOS ROM is 8kB vs. the 16FDC's 4kB.
In any case, the memory boards are usually configured to map out the upper
32kB.