Why is CP/M faster than DOS

From: Hans Franke <Hans.Franke_at_mch20.sbs.de>
Date: Fri Sep 3 13:04:38 1999

> After reading all the comments on CP/M computers a comment was made that CP/M
> is a faster OS that DOS.. I have found this to be very true.
> My Kaypro 1X boots up in 5 seconds, and loads MBASIC in about another 5
> seconds, also
> executes the same BASIC code faster than on my XT.

> Now on my old Compaq XT, it takes about 30 seconds just for the hardware to
> powerup,
> then another 20 seconds to boot to a DOS prompt, then another 15 seconds to
> boot BASIC.

> So can some of the experts here tell me why CP/M is so much faster ?

Well, you should skip the hardware power up time when compareing,
since most old systems didn'n check anything at all, so its
5+5 vs. 20+15. Now take the more sophisticated OS into account.
MS-DOS (I assume something like 2.11 or higher) is a _way_ more
complex system (loadable device driver etc.) while CP/M is just
a memory image with some adjustments. If you take DOS 1.x _without_
any additional stuff, the needed time to boot gets _very_ close.
Further on, CP/M is barely more than a programm loader, while MS-DOS
offers quite more abstraktion - in fact, the CP/M functionality
is more like the PC-BIOS (I still won't call MS-DOS an OS either).
Next the programm structure on file is a bit more complex than just
loading the image - additional processing is needed. And finaly,
the Coding is bigger - this results in way longer loading times,
since the media (Minidisks) are at the same transfer rate.

Oh, and last but not least: If you compare a Z80 4MHz to an 8088 4.77MHz,
you get a very close finish ... especialy when the programm isn't realy
adapted to the processors - and most of the early apps have just been
(more or less) automatic conversion of 8080 code.


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Received on Fri Sep 03 1999 - 13:04:38 BST

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