Recommended DOS Versions

[Chuck(G)]

Calculating free space on a disk when you're running in real 16-bit mode is going to take time, even if you're running on a Pentium. FAT32 for large disks only really became practical when it could be done as a 32-bit task.

 

[Maverick1978]

fwiw, I'll second this - I found the same thing on my IDEjr, which (currently) is the only 8088 that has drives greater than 256mb in there (I have an 8gb DOM in the IDEjr). FWIW, when using the XT-IDE in my XT with the 256mb or 1gb CF, it was only a few seconds to recalculate free space, no more than about 8 seconds at most.

At a straight DOS prompt, the behavior is 100% predictable. If you run programs that issue DOS function calls that perform absolute reads/writes (INT 25h/26h), or anything else DOS feels may have modified anything outside of its control, DOS marks the free space variable as "dirty" and it is recalculated the next time it is needed. So, this is common:

DIR (slow)
DIR (fast)
DIR (fast)
...
DIR (fast)
CHKDSK C:
DIR (slow)

 

[Ole Juul]

Calculating free space on a disk when you're running in real 16-bit mode is going to take time, even if you're running on a Pentium.

I guess I'm not understanding. How is this time calculated? I certainly can't readily perceive it in practice. Chkdsk takes a noticeable fraction of a second, but DIR is visually instant both before and after that. The practical limits seem to be in the speed of the video rendering. Although I do understand that doing a bunch of code in a program or batch file then it could add up to something that a user could see. Does that happen in practice though?

 

[Trixter]

If you're not seeing a delay the first time you run DIR, then you must not be on an 8088 system running DOS 4 or later with a full FAT16 filesystem (ie. 2G, 1G, 512M, 256M, 128M all use up nearly the entire full FAT16 capacity, differing only by cluster size). Any FAT12 filesystem does not have this problem (32M or less); also, 286s and later don't have this problem.

I can post a video if people are having trouble visualizing this...

 

[Ole Juul]

If you're not seeing a delay the first time you run DIR, then you must not be on an 8088 system running DOS 4 or later with a full FAT16 filesystem (ie. 2G, 1G, 512M, 256M, 128M all use up nearly the entire full FAT16 capacity, differing only by cluster size). Any FAT12 filesystem does not have this problem (32M or less); also, 286s and later don't have this problem.

Although I don't have an 8088 system turned on at the moment, I wasn't doubting that. Chuck said "even on a Pentium", so that's what I was responding to. This is a P133 with FAT16.