Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP
Posting-Version: version B 2.10.2 9/18/84; site psivax.UUCP
Path: utzoo!watmath!clyde!cbosgd!ihnp4!houxm!vax135!cornell!uw-beaver!tektronix!decvax!ittvax!dcdwest!sdcsvax!sdcrdcf!psivax!al
From: al@psivax.UUCP (Al Schwartz)
Newsgroups: net.micro.pc
Subject: Re: Dos Startup modification
Message-ID: <307@psivax.UUCP>
Date: Mon, 4-Feb-85 21:18:38 EST
Article-I.D.: psivax.307
Posted: Mon Feb  4 21:18:38 1985
Date-Received: Sat, 9-Feb-85 04:53:43 EST
References: <11841@gatech.UUCP>
Reply-To: al@psivax.UUCP (Al Schwartz)
Distribution: net
Organization: Pacesetter Systems Inc., Sylmar, CA
Lines: 33
Summary: 


In article <11841@gatech.UUCP> klute@gatech.UUCP (Gregory Kenley) writes:
>A while back I remember reading an article in either PC or PC-Tech regarding
>modifying DOS on startup to skip the memory test.
>Gregory Kenley
>CSNet:  klute @ GATech		ARPA:  klute%GATech.CSNet @ CSNet-Relay.ARPA
>uucp:	...!{akgua,allegra,hplabs,ihnp4,linus,seismo,ulysses}!gatech!klute

The memory test code for the IBM is contained in the ROMS that are plugged
into the motherboard of the machine.  The memory has to be tested first
before the DOS can be booted in.  Therefore to make this change in software
one must make new ROMS (very expensive).  One way I can think of doing this
though, is to set your memory size switches on the motherboard for a lesser
memory size (so that only that amount will be tested by the ROM code) and
then later change the memory location(s) that the DOS (or BIOS) uses to
keep track of the memory size.  That way the programs that you run will know
how much memory.  You will also have to run a program that ignores parity
errors and then reads each location of memory that
was not tested in order to set the parity bit correctly, otherwise you'll
get a parity error when you attempt to use the memory.
This will only work with DOS versions less than 2.0.  In DOS 2.0 they added
a memory management scheme that allocates memory when
booted to correspond to the switch settings.  Any attempt to allocate more
than the switch settings were set to will cause the memory allocate
algorithm to fail.

My IBM PC takes 51 seconds to test the RAM (640K).  Thats just enough time
to go out an get a beer and pretzels.
-- 
Yow! Am I having fun yet?             Al Schwartz
                                      Pacesetter Systems Inc., Sylmar, CA 
{trwrb|allegra|burdvax|cbosgd|hplabs|ihnp4|sdcsvax|aero|uscvax|ucla-cs|
 bmcg|sdccsu3|csun|orstcs|akgua|randvax}!sdcrdcf!psivax!al