Why is CP/M faster than DOS

From: allisonp_at_world.std.com <(allisonp_at_world.std.com)>
Date: Fri Sep 3 11:59:36 1999

> since most old systems didn'n check anything at all, so its

Most yes but not all. My Visual 1050 does a powerup test then tests to
see what the boot device (floppy or winni) is useable. Still faster!

As to device loadability and images on disk. CPM generally is loaded as
an image on disk for versions up to CPM3. CPM3, MPM and CPM86 (68k too)
All load a loader that is core file system and that loaded loads a file
called CPM.sys though in some causes it will load peices and link them.

The most accurate statement about cpm (commonly 2.2) is that it prohibited
nothing. Loadable devices can and was done, though most BIOSs were pretty
bare. So if you wanted loadable devices and what not it was quite doable
and the ZCPR system was one such example. Even TSR programs were done
such as Handyman for example.

> Further on, CP/M is barely more than a programm loader, while MS-DOS

More correctly it is a complete file system. The CPP was at 2k barely
more than a file loader. There was nothing to prevent you from replacing
CCP with your own (ZCCP, ZCPR, CCP+ examples).

If I could make one comment rre were the system before about 82'sih that
had a bios that used interrupts. Example like the Vt180 or later years
AMproLB began to show what the CPM was capable of.

> 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.

This is true for both. The CPM image is 8080 code and if optimized for
z80 it's both smaller and faster. Running CPM (P2dos a z80 clone) on a
10mhz z80 with 128k of ram via paged MMU and fast DMA floppy and hard
disks is a shockingly fast machine in actual use. I know my s100 crate
is exactly this. The CPM version is stil 2.2 via the clone but all of the
mods like ZCPR, loadable devices, TSRs, RSXs are in there and quite
pleasent to use. I also have background print spooling, background
loadable programs (simple timeshare) implmented. it was quite easy to do
in that CPM does not prohibit it (it just doesn't do it)

Allison
Received on Fri Sep 03 1999 - 11:59:36 BST