>To refreshen your memory:
>I proposed earlier to use for both BIOS-routine 0144h and
>diskROM-entry 4010h the following change, to allow the use of bigger
>sector numbers:
>
>if bit 7 of drive number=0, then all parameters as usual,
>if bit 7 of drive number=1, then
>
> DE-register = pointer to 32-bit sector number
Yesterday I discovered something very interisting about MegaSCSI: entry
#4010 DOES support 23 bit sector numbers!!! How the hell? Easy: register C
is used for pass the media ID in standard #4010 entries. MegaSCSI maintains
it, but only in the case that bit 7 is 1. If bit 7 is 0, the rest of the
register C is interpreted as bits 22-16 of the sector number. Have others
interfaces this feature too?! In such case, a FAT16 driver will work with
any device!!
Your method is good, but I propose an alternative one: if bit 7=1, DE-HL
contains sector number, and data is transferred to DTA area; or then C
contains the high byte of memory address and low byte is supposed to be
zero... there are milions of alternatives! 8-) By the way, have you, or
someone, information enough about disk ROM for perform such changes?
>Well, I see 10 GB. and bigger drives NOW, and far bigger ones coming
>(soon). -> 24 bit sector number usefull NOW (not in a year), 32 bit
>sector number support usefull SOON (MAYBE in a year from now, maybe
>even sooner).
24 bit useful now, not in a year? Maybe are you exagerating a little?! If
we can use FAT16, it will be enough for a lot of years, I think! You really
need to have more than 2Gb per partition?!
Anyway, OK, if you are considering to make a whole new DOS, it is woth to
make 32 bit sector support instead of 24. But for a simple FAT16 patch (the
most urgent now I think), it is enough with 24 bit sector numbers. Just this!
>So, I propose to extend DOS function calls
>2Fh & 30h (absolute disk read/write) as follows:
>
>If bit 7 of drive number (in L register) = 0: all parameters as usual
>If bit 7 of drive number = 1:
>
> DE = low 16 bit of sector number (was: sector number)
> IX = high 16 bit of sector number (was: unused)
This is the best solution I think.
>How to determine the presence of features
>I think function #71 hex would be free for
>this purpose, and I suggest calling this: 'get feature info'.
What about extended BIOS? Just as DOS memory mapper support routines!
-----------------------------------------------------------------------------
Konami Man - AKA Nestor Soriano (^ ^)v - Itsumo MSX user
http://www.geocities.com/SiliconValley/Bay/9797/msx.htm
[EMAIL PROTECTED] ICQ#: 18281450
"In Windows 98, 3.000 found failures of W95 have been corrected..."
Translation: 3.000.000 not found failures continue without being corrected...
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