MirrorRepos/RomWBW
1
0
Fork 1
mirror of https://github.com/wwarthen/RomWBW.git synced 2026-02-06 22:33:12 -06:00
Code Issues Projects Releases Wiki Activity

Doc Fixes per HubertH

Browse Source 
See Issue #415.  This commit is intended to clarify the documentation with respect to this issue.  Thanks and credit to HubertH.
This commit is contained in:
Wayne Warthen
2024-09-03 15:04:50 -07:00
parent 9e6780a248
commit e07c38dc1a
8 changed files with 22 additions and 5 deletions
Download Patch File Download Diff File Expand all files Collapse all files

23
Source/Doc/SystemGuide.md
View File

@@ -847,12 +847,19 @@ more of the defined media types.
| MID_FD111 | 9 | 8" 1.11M Floppy |
| MID_HD1K | 10 | Hard Disk (LBA) w/ 1024 directory entries |
**NOTE**: HBIOS does not actually differentiate between MID_HD512 and
MID_HD1K. The use of these two formats is determined by the use of a
partition table on the media and is implemented by the operating
system itself. HBIOS treats all hard disks as raw sectors. See
[Function 0x18 -- Disk Media (DIOMEDIA)] for more information on the
Media ID byte returned.
HBIOS supports both Cylinder/Head/Sector (CHS) and Logical Block
Addresses (CHS) when locating a sector for I/O (see DIOSEEK function).
For devices that are natively CHS (e.g., floppy disk), the HBIOS driver
can convert LBA values to CHS values according to the geometry of the
current media. For devices that are natively LBA (e.g., hard disk), the
HBIOS driver simulates CHS using a fictitious geometry provided by the
HBIOS driver simulates CHS using a fictitious geometry provided by the
driver (typically 16 sectors per track and 16 heads per cylinder).
### Function 0x10 -- Disk Status (DIOSTATUS)
@@ -1065,6 +1072,12 @@ Report the Media ID (E) for the for media in the specified Disk Unit
will be performed. The Status (A) is a standard HBIOS result code. If
there is no media in device, function will return an error status.
**NOTE**: This function will always return MID_HD512 for hard disk
devices. MID_HD1K is provided for use internally by operating systems
that provide different filsystem formats depending on the partition
table. This function cannot be used to determine if an HD1K formatted
partition exists on the hard disk.
### Function 0x19 -- Disk Define Media (DIODEFMED)
| **Entry Parameters** | **Returned Values** |
@@ -1098,7 +1111,7 @@ DIOMEDIA function to force this if desired.
| **Entry Parameters** | **Returned Values** |
|----------------------------------------|----------------------------------------|
| B: 0x1B | A: Status |
| C: Disk Unit | D: Heads |
| C: Disk Unit | D: Heads / LBA |
| | E: Sectors |
| | HL: Cylinder Count |
| | BC: Block Size |
@@ -1108,7 +1121,11 @@ device uses LBA mode addressing natively, then the drivers simulated
geometry will be returned. The Status (A) is a standard HBIOS result
code. If the media is unknown, an error will be returned.
Heads (D) refers to the number of heads per cylinder. Sectors (E)
LBA capability is indicated by D:7. When set, the device is capable
of LBA addressing. Refer to [Function 0x12 -- Disk Seek (DIOSEEK)]
for more information on specifying LBA vs. CHS addresses.
Heads (D:6-0) refers to the number of heads per cylinder. Sectors (E)
refers to the number of sectors per track. Cylinder Count (HL) is the
total number of cylinders addressable for the media. Block Size (BC)
is the number of bytes in one sector.