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Re: BootProg released

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On Wed, 01 Jul 2015 11:02:17 +0100, James Harris  
<james.harris.1@gmail.com> wrote:

> "Alexei A. Frounze" <alexfrunews@gmail.com> wrote in message  
> news:ca5622b0-3742-49d5-a136-a6af5b808d9c@googlegroups.com...
>> On Monday, June 22, 2015 at 6:12:45 AM UTC-7, James Harris wrote:
>>> "Alexei A. Frounze" <...@gmail.com> wrote in message
>>> news:8029ab57-0054-4410-aba8-d5189f025db7@googlegroups.com...
>>>
>>> ...
>>>
>>> What CPU does your code require? And what does it report if booted on  
>>> an
>>> older CPU? You know my preferences on this. ;-)
>>
>> Jim Leonard (the author of the 8088 Corruption, 8088 Domination and
>> 8088 MPH) has recently expressed interest in making an 8086/8088 version
>> and it looks like the FAT12 variant can be made 8086/8088-compatible
>> (perhaps, with a few minor features removed). :)

It's just the pusha and popa that aren't available, AFAICT.

>
> I have looked up Jim Leonard's work that you mentioned. I had heard the  
> name but was not familiar with it before. Very impressive!
>
> My own fat boot sector is pure 8086 code. As it is intended for starting  
> an OS I made a number of choices for reliability:
>
> * It carries out quite a lot of checks of diskette geometry before it  
> starts - e.g. to ensure that the values are such that mutlibyte  
> arithmetic won't overflow.
>
> * It sticks to 8086 code so that it cannot simply fail without issuing  
> an explanation as to why it has failed.
>
> * It prints progress info largely so that if something goes wrong (bad  
> sector, file not found, bad disk setup) the user can see where the error  
> occurred.
>
> As OS developers often like to do things themselves I chose to have the  
> boot sector do nothing more than load the next file. The loaded file  
> starts with there having been no mode changes, no A20 changes, and no  
> checks carried out other than those which were necessary to ensure that  
> the load completes or reports. The loaded file is effectively just  
> another boot 'sector' but larger.
>
> Things I would like to add if I can make space:
>
> * Further reports, especially retries of reads so the user can see if a  
> read fails once or twice and then works.
>
> * Move code so that the loaded file can start at 0x7c00.
>
I still don't get why this has to be; just because MS coded it that way.


> * Read the graphics card current page rather than just forcing it to  
> zero.
>
seems if you're cold booting there shouldn't be any question as to any  
previous page.

> Given your comments about FAT32 needing most space I may wait until I  
> have a FAT32 version working before I try to add any extras, so that all  
> three versions can be the same.
>
> James
>

Didn't we have a compo to create minimal code for a boot sector not so  
long ago?



-- 
Bah, and indeed, Humbug

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Thread

BootProg released "Alexei A. Frounze" <alexfrunews@gmail.com> - 2015-06-21 22:52 -0700
  Re: BootProg released "James Harris" <james.harris.1@gmail.com> - 2015-06-22 14:12 +0100
    The BIOS Drive ID urban legend "Mike Gonta" <mikegonta@gmail.com> - 2015-06-24 17:49 -0400
      Re: The BIOS Drive ID urban legend (was: BootProg released) "James Harris" <james.harris.1@gmail.com> - 2015-07-01 10:44 +0100
    Re: BootProg released "Alexei A. Frounze" <alexfrunews@gmail.com> - 2015-06-25 21:08 -0700
      Re: BootProg released "James Harris" <james.harris.1@gmail.com> - 2015-07-01 11:02 +0100
        Re: BootProg released "Alexei A. Frounze" <alexfrunews@gmail.com> - 2015-07-04 05:18 -0700
        Re: BootProg released "Kerr Mudd-John" <admin@127.0.0.1> - 2015-07-05 19:11 +0100
          Re: BootProg released "Kerr Mudd-John" <admin@127.0.0.1> - 2015-07-06 10:52 +0100
            Re: BootProg released "James Harris" <james.harris.1@gmail.com> - 2015-07-06 21:42 +0100

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