AMSDOS Memory Map - Revision history

Poliander: /* Extended Disk Parameter Block (DPB,CSA,ALT) for Drive A/B */

2024-04-13T09:49:28Z

‎Extended Disk Parameter Block (DPB,CSA,ALT) for Drive A/B

2024-04-13T09:46:54Z

‎XDPB - Extended Disk Parameter Block (DPB,CSA,ALT) for Drive A/B

2024-04-13T09:46:39Z

2024-04-13T09:46:27Z

2024-04-13T09:44:58Z

‎Extended Disk Parameter Block (DPB,CSA,ALT) for Drive A/B

2024-04-13T09:17:41Z

2020-11-18T09:54:05Z

Fix description for BE42 (points to drive A, not B)

2018-01-22T20:21:36Z

2018-01-22T20:20:06Z

‎Disk Parameter Header (DPH) for Drive A/B

2018-01-22T20:19:43Z

@@ Line 102: / Line 102: @@
 Eh  2 ALV    Pointer to ALT (A8B9h/A8F9h for Drive A/B) Allocation Table
-== Extended Disk Parameter Block (DPB,CSA,ALT) for Drive A/B ==
+== Extended Disk Parameter Block (XDPB,CSA,ALT) for Drive A/B ==
 h  2 SPT   Records per Track (CPM/Data=36, IBM=32)
 h  1 BSH   Block Shift (3) (records per block = 1 SHL N)

@@ Line 102: / Line 102: @@
 Eh  2 ALV    Pointer to ALT (A8B9h/A8F9h for Drive A/B) Allocation Table
-== XDPB - Extended Disk Parameter Block (DPB,CSA,ALT) for Drive A/B ==
+== Extended Disk Parameter Block (DPB,CSA,ALT) for Drive A/B ==
 h  2 SPT   Records per Track (CPM/Data=36, IBM=32)
 h  1 BSH   Block Shift (3) (records per block = 1 SHL N)

@@ Line 125: / Line 125: @@
 h 23 ALT   Block Allocation Table (23x8bit = 184bit) (only 180bit used)
-=== Finding the XDPB for a drive ==
+=== Finding the XDPB for a drive ===
 The 2 byte pointer at &BE40 points to a list of DPH structures,  1 per drive, listed in order.

@@ Line 91: / Line 91: @@
 h  3 24bit Filepos in CHARs, or 16bit Filesize if non-ASCII file
 h  2 Checksum accross [05h..47h]
 == XDPB - Extended Disk Parameter Block (DPB,CSA,ALT) for Drive A/B ==
@@ Line 115: / Line 125: @@
 h 23 ALT   Block Allocation Table (23x8bit = 184bit) (only 180bit used)
-== Disk Parameter Header (DPH) for Drive A/B ==
+=== Finding the XDPB for a drive ==
-h  2 XLT    Skew Factor Translation (physical-to-logical sector) (not used)
-h  2 TRACK  Current Track (misused as DIRNUM by AMSDOS)
-h  2 SECTOR Current Sector
-h  2 DIRNUM Current Directory Number
-h  2 DIRBUF Pointer to Directory Buffer (A930h)
-Ah  2 DPB    Pointer to DPB/XDPB (A890h/A8D0h for Drive A/B) Drive Param Block
-Ch  2 CSV    Pointer to CSA (A8A9h/A8E9h for Drive A/B) Checksums
-Eh  2 ALV    Pointer to ALT (A8B9h/A8F9h for Drive A/B) Allocation Table
-−
 == Finding the XDPB for a drive ==
 The 2 byte pointer at &BE40 points to a list of DPH structures,  1 per drive, listed in order.

@@ Line 92: / Line 92: @@
 h  2 Checksum accross [05h..47h]
-== Extended Disk Parameter Block (DPB,CSA,ALT) for Drive A/B ==
+== XDPB - Extended Disk Parameter Block (DPB,CSA,ALT) for Drive A/B ==
 h  2 SPT   Records per Track (CPM/Data=36, IBM=32)
 h  1 BSH   Block Shift (3) (records per block = 1 SHL N)

@@ Line 130: / Line 130: @@
 In most AMSTRAD dos there is space for 2 only.
-To get the XDPB for a drive (this works on [[VDOS]], [[X-DDOS]], [[AMSDOS]] and [[Parados]]:
+To get the XDPB for a drive (this works on [[VDOS]], [[X-DDOS]], [[AMSDOS]] and [[ParaDOS]]:
     ;; A = drive

@@ Line 3: / Line 3: @@
 == AMSDOS RAM 1 (always at BE40h..BE7Fh) ==
    BE40   2 Pointer to CP/M DPH for Drive A and drive B  (A910h) (CPM:AE58h) (see below)
-   BE42   2 Pointer to XPDB for Drive B                  (A890h) (CPM:ADD8h)
+   BE42   2 Pointer to XPDB for Drive A and drive B      (A890h) (CPM:ADD8h)
    BE44   2 Delay for Motor Spin-up in 1/50 seconds      (0032h)
    BE46   2 Delay for Motor Spin-down in 1/50 seconds    (00FAh)

← Older revision		Revision as of 20:21, 22 January 2018
Line 1:		Line 1:
−	AMSDOS uses two memory blocks. The first is always at BE40h..BE7Fh (on the 464 this region was used as Stack). The second is allocated from User RAM, typically located at A700h..ABFFh (unless other expansion ROMs with higher ROM bank number have already allocated RAM at that locations).	+	AMSDOS uses two memory blocks. The first is always at BE40h..BE7Fh (on the 464 this region was used as Stack). The second is allocated from User RAM, typically located at A700h..ABFFh (unless other expansion ROMs with higher ROM bank number have already allocated RAM at that locations).

	== AMSDOS RAM 1 (always at BE40h..BE7Fh) ==		== AMSDOS RAM 1 (always at BE40h..BE7Fh) ==