At 03:47 PM 11/24/98 +0000, you wrote:
>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:
But you still haven't convinced me (and some others) why 4010 should be
updated instead of creating a new routine at a new address.
>This would insure 100% compatibility, have a negligable impact on
>performance, and easy to use for programmers.
It's not easy for the programmers of the HD BIOS. To fetch the sector
number, the memory it is in must be selected. But by the time the HD BIOS
looks up the sector number, a lot of slot switches have occured. Reading
the correct values would take an inter-slot-read, which is slow.
>For the BIOS/diskROM entries, it would pose a problem to define new
>entries; where to place such a new entry?
#4034 and beyond, plenty of space left.
>How to pass the extra info?
What "extra" info?
Because those would be new calls, you would have complete freedom in
choosing any way of passing parameters.
>If called with A=2 (get info on FAT16 support):
>returns:
> A=0: no FAT16 support
> A<>0: FAT16 supported
>Any extra info to be determined later, if necessary
More useful would be a call that tells you which filesystem is used on a
particular drive.
Imagine a system with both a FAT12 and a FAT16 partition active. Knowing
that FAT16 is supported is not enough, you have to know on which drives. To
make this more general: you want to ask which filesystem is used on a
certain drive.
>Only thing left then, would be finding a way for the system, to
>determine if a driver supports 32-bit sector number I/O, or not. I
>suggest using one of the existing diskROM-entries (preferably one of
>those besides 4010h), with some special input value, to determine
>this.
I suggest using a "magic number" identification. A short number or string
that is specific for 32-bit sector number compatible device driver ROMs.
Just like "OPLL" is used for FM-PAC.
Bye,
Maarten
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