Replies to Jack /and/ to Ralf follow in sequence.


>> On REAL (old) PC hardware, the existence of floppy disk changelines is  
>> not guaranteed [....]

> My design goal for UIDE/UIDE2 was to write a driver that uses as FEW
> "DOS system calls" as possible.    At present, UIDE/UIDE2 are more a
> "BIOS" than a "DOS" driver, and they need to handle only a BIOS "Int
> 13h" call after their initialization.   I did so (A) to have a SMALL
> driver, not a "Bloody MONSTER!" like SMARTDRV or Norton NCACHE2, (B)
> to avoid "DOS calls" that may NOT be implemented the same across all
>DOS systems, and (C) to follow the old U.S. engineering "joke" known
> as the "K.I.S.S. Principle" 

Understood and agreed with : I've not been "defending" MS smartdrive "against" 
UIDE - clearly they are not reciprocally substitutable, there are argumentss 
for, and against, either side, and also cases when it is not easy to choose. 
I've been mentionning smartdrive only for the fact that it allows the user 
explicitly remove one or several drive "letters" from caching, which is handy 
in some cases - not just floppies.  

> So, I DISPUTE your comments about the change lines being unreliable!
> They have "been around" from 1985, and if they ever DO fail, that is
> a "maintenance" problem for the user, NOT an indication that I ought
> to reconsider using them in UIDE/UIDE2!!

And I'm disputing your disputation :=)  Several brand floppy drives used in 
PC-AT compatibles in the 1980s were known to have problems with the change 
line, and also pre-AT drives might not have change lines at all, or no BIOS 
support. Nowadays people might still be using old drives they recovered from 
old stocks or dumps . 

MS-DOS took extreme care to avoid disk corruption, you may peek at the code if 
you are so inclined. Trusting the change line is /way/ too dangerous ! In fact 
that was the main reason driving MS to add more and more "unique" IDs to floppy 
boot sectors over the years and PC-DOS/MSDOS versions - including the bizarre 
xxxxxICH semi-random thing which Windows 95 (CHIcago) will overwrite the "OEM" 
field with.

>SMARTDRV ...  takes a LOT of memory and is very
> heavily linked to MS-DOS, so it may NOT run on other DOS systems!!
> Also, it has never been updated to use UltraDMA, ...
> UIDE/UIDE2 can do both.

> Delayed writes are nice, but you "PAY for them!" given the size of
> SMARTDRV and NCACHE2.  I felt it to be MUCH more reasonable if my
>drivers did a FAST Write-Through implementation, with UltraDMA and
> direct cache I-O, in only their "912 byte" upper-memory size!

Nobody is denying your drivers are sweet !

>>> -- UIDE2 has only 16 spare bytes before it goes back over a 7K
>>> .SYS file!   But, I shall find a way!
>> No doubt you will.

> In fact only 12 bytes, and I required only 11 of them for /N5, so
> UIDE2 still has 1 spare!   It is still a 7K-byte .SYS file and it
> can be "packed" using UPX down to 6K for use on "boot" diskettes!

Thanks !

Re: [Freedos-user] Virtual floppy change problem
Ralf A. Quint <FreeDOS@gm...> wrote :

"Anyway you slice it, that Virtual Box (and probably a few other VMs) 
are not properly supporting this is rather due to the ignorance of 
those VM developers and the stupid attitude of "nobody is using 
floppy disks anymore". It is a very well known function, relatively 
easy to implement, so it should be up to the VM developers to do so..."

Agreed. I would complain to them, were I a VBox user - I do VMware and Virtual 
PC rather, and I have not noticed a problem with change lines in these (shall 
try, specifically, UIDE diskette caching in both, and Bochs,  and report back).

> just my 2c,

But worth a dime (at least)  


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