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Czech republic,
30.12.2015, 14:29

Very slow disk access in FreeDOS (Users)

I suspected that FreeDOS disk access is slower than disk access from MS-DOS 7.1 but until yesterday I didn't know how much.

For tests I used tool RAWSPEED by Rayer.
My primary (master) disk is SSD, and the secondary is older HDD.
In FreeDOS I get about 6.5MB/sec on SSD in both reading and writting. On HDD about 2MB/sec - again, both for reading and writting.
The presence/absence of XIDE has only minimal effect, the pure setup without CONFIG.SYS and AUTOEXEC.BAT also do not differ much by my full setup with V86 mode provided by JEMMEX.

But with MS-DOS 7.1 (pure boot without any drivers) I get on SSD about 16MB/sec with writes and about 34MB/sec with reads!
And on HDD 3,7MB/sec writting and 32MB/sec(!) reading.
Variant with MS-DOS and XIDE I didn't try yet.

Both disks are FAT32 formatted are about 60GB size
Why the hell the FreeDOS slows down my SSD disk?
I write this post in work the numbers I write from head but they are roughly correct.
Is possible that FreeDOS uses some timers for disk operation which slow down the access?

And is the RAWSPEED appropriate tool for such measurement? What does it measure? Does it use INT 25h/26h interface or INT13h calls?




missing nowhere,
31.12.2015, 13:19

@ Laaca

Very slow disk access in FreeDOS

As an option, try these DOS tools:
HDDSpeed and c't Magazin ( ) ;-) h2bench
And report results.
Link is here:


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Berlin, Germany,
31.12.2015, 17:10

@ Laaca

Very slow disk access in FreeDOS

Some more benchmark tools: (Yes, some links don't work anymore.)

I recommend SPEEDSYS to you. Then you can compare your results with some of my old machines:

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