Hi, Guys! Replying to self, sort of, and Jeremy at the same time. 
I've been glancing thru the ram disk, TDSK, source. Internal buffer (used for 
init only) was provisionned for one 4K sector, but for some reason author(s) 
limited sector size to 2K, as specified on the driver's command line. 

I boldly hacked the binary so it ignored the limitation and, behold, a first 
quick and (very) dirty test of a ~8 MBytes FAT12 based RAM disk *with 4096 byte 
sectors* in MS-DOS 7.1 with a rather fully loaded config SUCCEEDED! I was able 
to copy several megabyte files to/from the ramdisk (quick tests did include 
binary compare fo source to dest, and an examination of the RAMdisk with 
Norton's DISKEDIT revealed no problems).

I'm not affirming yet there are no hidden bugs but, clearly, MSDOS CAN support 
this type of device with no or little problems ! This to me is great news, 
since it makes it worth developing a simple ASPI to DOS convertor for use with 
my external USB disk. MSDOS bugs, if any, may be limited to installing large 
sectored units which are to be managed by IO/MSDOS.SYS internal disk driver.

Jeremy wrote :
> (currently not while testing). ?I have tested 256, 512,
> 1024, and 2048
> byte sectors with tdsk (currently my only way to test).

You may try to force TDSK to allow 4096 bps (not more without recompilation) by 
nullifying the sanity test for command-line size-of-sector, like I did !


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