AT Compatible DOS Application

to PC-9800 Series

Considering Software Localization

September 1996
First Edition

Overview

• Memory Map

  In PC-9800, there are two kinds of architecture, normal resolution mode and high resolution mode of which the video resolution and memory map differs. High resolution mode is a mode that is made with a special usage, such as CAD, in mind. Since high resolution can be realized using graphic accelerator on a normal resolution mode, only the memory map of the normal resolution will be considered here. PC-9800 memory map is very similar to AT compatible machines. As long as the API of the operating system is used, you should not worry about their differences.

   

  AT Compatible machines Addresses PC-9800 0000:0000 Interrupt Vector   Interrupt Vector 0040:0000 BIOS Work Area   BIOS Work Area 0050:0000   Conventional Memory 0060:0000     Conventional Memory       9FC0:0000   BIOS Work Area     A0000:0000 Video RAM   Text RAM   A400:0000     CG Window   A500:0000   A800:0000     Graph RAM C000:0000 VGA Bios   I/O C800:0000   I/O     E000:0000 For BIOS Extension   Graph RAM   E800:0000 F000:0000 BASIC/BIOS ROM BIOS ROM     FFFF:0010

  The following address range can be used as an UMB.

  A500-A7FF

  Maintenance of extended memory is compatible when API's of XMS, EMS or DPMI are used.

  
  
  
• To distinguish between AT compatible machines and PC-9800

  The best way to distinguish between AT compatibles and PC-9800 is to check the data following the ROM BIOS entry point (FFFF:0000). This area*s data format is shown below. The date is written in ASCII code, so when the separator "/" (2Fh in hexadecimal) is not present, it is PC-9800. One should check FFFF:0007 and FFFF:000A. This detection method assumes that machines other than AT compatibles are PC-9800.

  Address	Length	AT Compatibles	PC-9800
  FFFF:0000	5 Bytes	JMP far	JMP far
  FFFF:0005	8 Bytes	Date 'mm/dd/yy'	Not used
  FFFF:000D	1 Byte	Not used	Not used
  FFFF:000E	1 Byte	Model ID	ROM checksum
  FFFF:000F	1 Byte	Reserved	ROM checksum

• I/O Port

  I/O port addresses of AT compatible machines and PC-9800 are almost all different. Same devices such as DMA controller and interrupt controller are used, but their addresses differ. In the AT compatibles, I/O addresses of the onboard controller are continuous, but in PC-9800, they are on the odd addresses or on the even addresses, thus not continuous.

  When localizing, one must modify the device*s offset address and the base I/O address. In AT compatibles, to access the next I/O port, one could just add one to the base I/O address, but in PC-9800, one must add two to the base address. On the option boards, since it depends on the board*s architecture, the above method might not apply.

  I/O Port Comparison (0000-00FF)

  Address	AT Compatible	PC-9800
  		Even Number	Odd Number
  0000-000F	DMA Controller	Interrupt Controller 12	DMA Controller
  0010-001F
  0020-002F	Interrupt Controller 1	Real Time Clock	DMA Bank
  0030-003F		COM 1	System Port
  0040-004F	Timer	LPT 1	Keyboard
  0050-005F		NMI Control	320 KB Floppy Disk
  0060-006F	Keyboard	Text Display Control
  0070-007F	Real Time Clock		Timer
  0080-008F	DMA		OMNI NET
  0090-009F			For System
  00A0-00AF	Interrupt Controller 2	Graphic Control	CG Control
  00B0-00BF		HDLC/SDLC, COM 2, COM 3
  00C0-00CF	DMA Controller	SCSI, Floppy Disk	GP-IB
  00D0-00DF		For User
  00E0-00EF
  00F0-00FF	Math Coprocessor 80287	For User, Intel Reserve

  I/O Port Comparison (0100-01FF)

  Address	AT Compatible	PC-9800
  		Even Number	Odd Number
  0100-010F		System Reserve
  0110-011F		(On a old machine, this is a copy of 0000-00FF)
  0120-012F
  0130-013F
  0140-014F
  0150-015F
  0160-016F
  0170-017F
  0180-018F		Sound
  0190-019F
  01A0-01AF
  01B0-01BF
  01C0-01CF
  01D0-01DF
  01E0-01EF
  01F0-01FF	Fixed Disk

  I/O Port Comparison (0200-02FF)

  Address	AT Compatible	PC-9800
  		Even Number	Odd Number
  0200-020F	Game Port	System Reserve
  0210-021F		(On a old machine, this is a copy of 0000-00FF)
  0220-022F
  0230-023F
  0240-024F
  0250-025F
  0260-026F
  0270-027F	LPT 2
  0280-028F
  0290-029F
  02A0-02AF
  02B0-02BF	Alternate EGA
  02C0-02CF
  02D0-02DF
  02E0-02EF
  02F0-02FF	COM 2

  I/O Port Comparison (0300-03FF)

  Address	AT Compatible	PC-9800
  		Even Number	Odd Number
  0300-030F		System Reserve
  0310-031F		(On a old machine, this is a copy of 0000-00FF)
  0320-032F
  0330-033F
  0340-034F
  0350-035F
  0360-036F
  0370-037F	LPT 1
  0380-038F	Synchronous Controller 2
  0390-039F	Cluster Adapter
  03A0-03AF	Synchronous Controller 1
  03B0-03BF	MDA, LPT 1
  03C0-03CF	EGA
  03D0-03DF	CGA
  03E0-03EF
  03F0-03FF	Floppy Disk, COM 1

  
  
  
  

• Interrupt Vector

  There are differences in allocation of hardware interrupts and BIOS interrupts in the interrupt vector. The application should not use the hardware and BIOS interrupts as much as possible. The application should use the API's that are provided by the operating system. Device drivers that controls the hardware may use the hardware interrupt vector, but you should note that the interrupt number of the slave of the interrupt controller differs and the number of nested level differs.

  Interrupt vector comparison (INT 00H-1FH)

  Vector Number	AT Compatibles		PC-9800
  00 01 02 03 04 05 06 07 08 09 0A 0B 0C 0D 0E 0F 10 11 12 13 14 15 16 17 18 19 1A 1B 1C 1D 1E 1F	Divide by 0 Exception Single Step NMI Breakpoint Overflow Screen Hard Copy Reserved Reserved Timer Keyboard Slave COM 1 COM 2 LPT 2 Floppy Disk LPT 1 Video Machine Structure Memory Size Disk Communication Extension Keyboard Printer BASIC Startup Bootstrap Time BREAK key Timer Clock Video Parameter Disk Parameter Graphics Character	CPU CPU CPU CPU CPU BIOS IRQ 0 IRQ 1 IRQ 2 IRQ 3 IRQ 4 IRQ 5 IRQ 6 IRQ 7 BIOS BIOS BIOS BIOS BIOS BIOS BIOS BIOS BIOS BIOS BIOS BIOS BIOS BIOS BIOS BIOS	Divide by 0 Error Single Step NMI Breakpoint Overflow COPY Key STOP Key Timeout Timer Keyboard V-SYNC Extended Bus INT 0 COM 1 Extended Bus INT 1 Extended Bus INT 2 Slave PIC NDP Hard Disk Floppy Disk Floppy Disk Sound Mouse None System Timer Keyboard/Text RS-232C Printer Disk Calendar Reserved ROM BASIC System	CPU CPU CPU CPU CPU BIOS BIOS BIOS IRQ 0 IRQ 1 IRQ 2 IRQ 3 IRQ 4 IRQ 5 IRQ 6 IRQ 7 CPU IRQ 9 IRQ 10 IRQ 11 IRQ 12 IRQ 13 IRQ 14 IRQ 15 BIOS BIOS BIOS BIOS BIOS BIOS BIOS BIOS

  Interrupt vector comparison (INT 20H-FFH)

  Vector Number	AT Compatibles		PC-9800
  20-3F 40 41 42 43 44 45 46 47-49 4A 4B-4F 50 51-59 5A 5B 5C 5D-66 67 68-6E 6F 70 71 72 73 74 75 77 78-7F 80-85 86-F0 F1-FF	Reserved for DOS Disk (INT 13H) Disk #0 Parameter Video (INT 10H) EGA Parameter Character Table Address Fixed Disk #1 Parameter Alarm Handler AT Alarm PC Cluster, Function PC Cluster, INT 19H PC Cluster, NET BIOS EMS Real Time Clock IRQ 2 Mouse Not Used Reserved for BASIC BASIC Not Used	- - - - - - - - - - - - - - - - - - - - IRQ 8 IRQ 9 IRQ 10 IRQ 11 IRQ 12 IRQ 13 IRQ 14 IRQ 15 - - -	Reserved for DOS For User For User For User For User For User For User For User For User For User For User For User For User For User For User For User For User EMS For User Japanese Character FEP (ATOK) For User For User For User For User For User For User For User For User Reserved for BASIC Reserved for BASIC Reserved for BASIC

  Usually on AT compatibles, non-used vector value is 0000:0000, but on PC-9800, it points to the address that display the error message. Thus, you should not use the method that is used on the AT machines when checking whether or not the vector is used.

  
  
  
• Bootstrap

  On the PC-9800, there is no reboot function. To reboot, jump to FFFF:0000.

  On the AT compatible machines, the drive assignment of the operating system is fixed. E.G. A: is floppy disk, B: is floppy disk, C: is hard disk, etc... On PC-9800, normally the drive that started up the operating system is the A: drive. Thus, the application must not assume that the drive is fixed, especially the installation program. Applications and the installation programs should check what kind of drive it is by using the API's that are provided by the operating systems.

  For example, in MS-DOS, it is possible to determine if the drives are fixed, removable, local or remote by using the IoCtl function.