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From: anton@mips.complang.tuwien.ac.at (Anton Ertl)
Newsgroups: comp.arch
Subject: Re: tiny COBOL,  Article on new mainframe use
Date: Sat, 31 Aug 2024 17:29:57 GMT
Organization: Institut fuer Computersprachen, Technische Universitaet Wien
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Stefan Monnier <monnier@iro.umontreal.ca> writes:
>> A C64 had 64K 8-bit bytes of RAM,
>
>Indeed (tho, IIRC 8kB of those were hidden by the ROM, tho you could
>change the mapping to hide different 8kB at different time and thus
>access the full 64kB of RAM).

Actually, the C64 has 8+8KB of ROM (at $a000-$bfff and at
$e000-$ffff), and I/O at $D000-$DFFF and at $0-$1 that hide the RAM in
the default configuration.  You could configure the "MMU" to make all
RAM except the two locations at $0-$1 readable and writeable for the
CPU, but of course then you would have to bank-switch to access the
I/O or the OS (in the ROM at $e000-$ffff), so the common setup even if
BASIC was not needed was to have the I/O and the OS ROM visible, and
48KB of contiguous RAM readable and writable.

>> and the floppies held about 1.2MB but they were a
>> whole lot cheaper than 1311 disk packs.
>
>IIRC they held only ~170kB.

Yes, the 1541 gave us 170KB at a time.  Much later there was also the
1571, which was double-sided and thus doubled the capacity, and even
later the 1581 which gave 790KB of storage.  I stuck with the 1541,
for which I have an accelerator add-on.

- anton
-- 
'Anyone trying for "industrial quality" ISA should avoid undefined behavior.'
  Mitch Alsup, <c17fcd89-f024-40e7-a594-88a85ac10d20o@googlegroups.com>