Re: MSDOS before cyl 1024

From	"Carlos E.R." <robin_listas@es.invalid>
Newsgroups	comp.os.linux.misc
Subject	Re: MSDOS before cyl 1024
Date	2023-01-22 04:47 +0100
Message-ID	<48ou9jxumk.ln2@Telcontar.valinor> (permalink)
References	(3 earlier) <tqgq6a$2k44c$2@dont-email.me> <ea7t9jx7k1.ln2@Telcontar.valinor> <tqh3jv$2l37n$4@dont-email.me> <p6rt9jxg6f.ln2@Telcontar.valinor> <op.1y42zyqya3w0dxdave@hodgins.homeip.net>

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On 2023-01-21 21:53, David W. Hodgins wrote:
> On Sat, 21 Jan 2023 14:32:09 -0500, Carlos E.R. 
> <robin_listas@es.invalid> wrote:
>> On 2023-01-21 17:24, Marco Moock wrote:
>>> Am 21.01.2023 um 14:52:46 Uhr schrieb Carlos E.R.:
>>>
>>>> Today they only specify the LBA sector.
>>>
>>> Can old disks (non-LBA) still be used with them?
>>
>> That's a good question.
>>
>> I suspect that disks or BIOS had both for years.
>>
>> However, on MsDOS times common disks had the parallel cable or interface
>> (PATA) while now they all use SATA.
>>
>> I don't remember all the details :-)
>>
>> There was an even older interface, used by disks with stepper motors on
>> the head arm. That's what the IBM PC and compats used.
> 
> There are still systems in use that are affected by it. I'm currently using
> one. From lshw the bios firmware shows ...
>            vendor: American Megatrends Inc.
>            version: 1604
>            date: 10/16/2012
> 
> I have no idea why it's limited in this way. Once grub or whichever boot 
> loader I'm using takes control, it switches to using lba mode. It's only the 
> loading of grub stage2 that must be within the first 1024 cylinders.

It is simple, actually. The boot loader, which is very small, has to use 
the existing BIOS functions to read from the disk, thus it is subject to 
whatever limitations the BIOS has. Once the boot loader has loaded and 
passed control to some larger code that contains "modern" functionality 
to read from disk (usually the kernel), those limitations are gone.

Otherwise, the boot loader would have to be significantly bigger in 
order to replace the bios functionality to read hard disks of any type 
and size.

> 
> I have one sata spinning rust drive that I rarely use, and 3 sata sdd 
> drives. They all use lba mode. The bios is normally set to boot from the first 
> ssd drive.
> 
> Regards, Dave Hodgins

-- 
Cheers, Carlos.

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Thread

MSDOS before cyl 1024 vjp2.at@at.BioStrategist.dot.dot.com - 2023-01-20 15:10 +0000
  Re: MSDOS before cyl 1024 Marco Moock <mo01@posteo.de> - 2023-01-20 19:04 +0100
  Re: MSDOS before cyl 1024 Vilmos Soti <vilmos@soti.ca> - 2023-01-21 03:00 -0800
    Re: MSDOS before cyl 1024 Marco Moock <mo01@posteo.de> - 2023-01-21 13:23 +0100
      Re: MSDOS before cyl 1024 The Natural Philosopher <tnp@invalid.invalid> - 2023-01-21 13:43 +0000
        Re: MSDOS before cyl 1024 "Carlos E.R." <robin_listas@es.invalid> - 2023-01-21 14:52 +0100
          Re: MSDOS before cyl 1024 Marco Moock <mo01@posteo.de> - 2023-01-21 17:24 +0100
            Re: MSDOS before cyl 1024 "Carlos E.R." <robin_listas@es.invalid> - 2023-01-21 20:32 +0100
              Re: MSDOS before cyl 1024 Lew Pitcher <lew.pitcher@digitalfreehold.ca> - 2023-01-21 19:50 +0000
                Re: MSDOS before cyl 1024 "Carlos E.R." <robin_listas@es.invalid> - 2023-01-21 21:16 +0100
                Re: MSDOS before cyl 1024 Lew Pitcher <lew.pitcher@digitalfreehold.ca> - 2023-01-21 20:45 +0000
                Re: MSDOS before cyl 1024 The Natural Philosopher <tnp@invalid.invalid> - 2023-01-22 09:39 +0000
              Re: MSDOS before cyl 1024 "David W. Hodgins" <dwhodgins@nomail.afraid.org> - 2023-01-21 15:53 -0500
                Re: MSDOS before cyl 1024 "Carlos E.R." <robin_listas@es.invalid> - 2023-01-22 04:47 +0100
              Re: MSDOS before cyl 1024 The Natural Philosopher <tnp@invalid.invalid> - 2023-01-22 09:35 +0000
                Re: MSDOS before cyl 1024 "David W. Hodgins" <dwhodgins@nomail.afraid.org> - 2023-01-22 05:08 -0500
          Re: MSDOS before cyl 1024 Peter 'Shaggy' Haywood <phaywood@alphalink.com.au> - 2023-01-22 21:33 +1100
            Re: MSDOS before cyl 1024 "Carlos E.R." <robin_listas@es.invalid> - 2023-01-22 14:29 +0100
  Re: MSDOS before cyl 1024 vjp2.at@at.BioStrategist.dot.dot.com - 2023-01-22 20:13 +0000
    Re: MSDOS before cyl 1024 Marco Moock <mo01@posteo.de> - 2023-01-23 10:08 +0100
    Re: MSDOS before cyl 1024 Peter 'Shaggy' Haywood <phaywood@alphalink.com.au> - 2023-01-26 14:40 +1100

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