Why is CP/M faster than DOS

From: allisonp_at_world.std.com <(allisonp_at_world.std.com)>
Date: Thu Sep 2 09:14:02 1999

> 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 ?

Really simple... Command.com (even V1) is bigger that CPM complete, CCP,
BDOS and BIOS are typically around 6.5-8k on most cpm systems. to be fair
most CPM systems do not do a POST so that is a consideration too.

FYI: MS-basic for CPM is roughly 30k, the compiler is smaller.

So far I've show the code as smaller I may add in 1982 the typical z80 was
4 mhz and there were 6mhz parts around where the average XT was 4.77mhz
and the cpus use about the same number of cycles to do similar things
so the z80 was nearly as fast and ran a lot less code to do it all
typically faster. By 1985 286s were 8-10mhz and z80s to 8mhz (or z180s to
10mhz) were still beating them in text based apps... reason codebloat.

It's hard to beat compact efficient code on a good cpu.

An aside apple][s were quite able to beat XT PCs, someteimes with better
graphics. Reason, tight code.

Allison
Received on Thu Sep 02 1999 - 09:14:02 BST