New Commodore 64 is Finally Here--For Real! PC MAG Snip

Fred Cisin cisin at
Fri Jan 1 15:28:54 CST 2016

>> While, at the time, 2G seemed "infinite", even then, I was amused at the 2G 
>> limitation being due to the use of a SIGNED 32 bit number.  The size can be 
>> anywhere from -2147483648 to 2147483647.
>> By switching to an UNSIGNED 32, NT and the like made the limit 4G.

On Fri, 1 Jan 2016, Jim Brain wrote:
> I think it was actually the sectors per cluster number, which was -64 to 63, 
> I believe and then got changed to 0-128, meaning cluster sizes of 128 
> 512-byte sectors, or 64K clusters

Quite likely more than one place with limits.   It seems likely.
There was probably a tendency to treat all numbers as signed.
I do know that the 32 bit file size field in the DIRectory entries was 
processed by some DOS operations, including DIR as a signed number.
Replacing those four bytes with FF FF FF FF would result in a reported 
file size of -1 bytes.  Replacing it with 00 00 00 80 (LSB first) gave a 
reported file size of -2147483648

> I know folks will hate on the format, but I am extremely impressed with the 
> FAT format.  To go all the way from floppies to 4TB drives is impressive.

I think that it is just fine.  I prefer it over a list of blocks, that 
might result in needing multiple directory entries, such as CP/M or 
TRS-DOS.  I much prefer it over the need for contiguous space 
(UCSD p-system)

Even the original Macintosh disk format was essentially the same 
algorithms as MS-DOS FAT.

Besides MS-DOS, Microsoft made some "Stand-Alone BASIC" designs that used 
the same idea of DIRectory and separate linked list.  Albeit at seek 
center instead of track 0.   Radio-Shack Color Computer, NEC, Okidata, 
etc.  I've even seen a disk from a Russian computer with that type of 

Some of the histories of MS-DOS say that Tim Paterson, in building his 
QDOOS ("Quick and Dirty OS") place-holder while waiting for CP/M-86, got 
the idea for FAT from seeing Microsoft Stand-Alone BASIC "for NCR" at 
Microsoft's West Coast Computer Faire booth.  I was at that show, and saw 
NEC machines with it, but I've never seen an NCR Stand-Alone BASIC - did 
the histories goof?

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