Altair 8800 simulator

Ein CP/M-Simulator von Peter Schorn, basierend auf dem SIMH-Projekt. Emuliert wird ein 8080, Z80, diverse Floppy-Controller, MMU, etc.

http://schorn.ch/altair.html

the simulator features 8 simulated hard disks with a capacity of 8MB (HDSK0 to HDSK7). Currently only CP/M supports two hard disks as devices I: and J:.

Start:

altairz80.exe <conf>

z.B.

altairz80.exe cpm22

Ende:

^E
q{uit} or by{e} or exi{t}

statt ^E für die SIMH-Taste (WRU genannt), kann ein anderer Steuercode gesetzt werden, z.B.

; SIMH Key to ^G (orig 005 ^E)
SET CONSOLE WRU=007

das dskdef-Format für die 8MByte HDISK (Standardformat 8megAltairSIM, es gibt noch andere Formate, s. Quellcode!)

HDSK (standard simulated AltairZ80 hard disk with 8’192 kB capacity) 8 MByte HD Format:

# ALTAIRZ80 SIMH *dsk 8MB Harddisk (Type AZ80 HDSK)
diskdef 8megAltairSIMH
 seclen 128
 tracks 2048
 sectrk 32
 blocksize 4096
 maxdir 1024
 skew 0
 boottrk 6
 os 2.2
end
# ALTAIRZ80 SIMH *dsk MITS 88-DISK 137 Byte/Sektor
# speedball (copylib) skewtable
diskdef simh
 seclen 128
 tracks 254
 sectrk 32
 blocksize 2048
 maxdir 256
 skew 17
 boottrk 6
 os 2.2
 libdsk:type simh
end

The file format is that of SimH: a file image is just a stream of blocks.

d tracks[0-7] 254

The 88-DISK controller The MITS 88-DISK is a simple programmed I/O interface to the MITS 8-inch floppy drive, which was basically a Pertec FD-400 with a power supply and buffer board built-in. The controller supports neither interrupts nor DMA, so floppy access required the sustained attention of the CPU. The standard I/O addresses were 8, 9, and 0A (hex), and we follow the standard. Details on controlling this hardware are in the altairz80_dsk.c source file. The only difference is that the simulated disks may be larger than the original ones: The original disk had 77 tracks while the simulated disks support up to 254 tracks (only relevant for CP/M). You can change the number of tracks per disk by setting the appropriate value in TRACKS[..]. For example „D TRACKS[0] 77" sets the number of tracks for disk 0 to the original number of 77. The command „D TRACKS[0-7] 77" changes the highest track number for all disks to 77.

The 88_DISK is a 8-inch floppy controller which can control up to 16 daisy-chained Pertec FD-400 hard-sectored floppy drives. Each diskette has physically 77 tracks of 32 137-byte sectors each.

CPM 3 Byte Header + 128 Byte Daten + 6 Byte Trailer

1113536 = 2^6*127*137

libdsk unterstützt das Format mit Type „simh"

/* The SIMH disc image is assumed to be in a single fixed format, like the
 * MYZ80 disc image.
 *
 * Geometry:
 * 	254 tracks (presumed to be 127 cylinders, 2 heads)
 * 	 32 sectors / track
 * 137 bytes/sector: 3 bytes header, 128 bytes data, 6 bytes Trailer

d:\user\pohlers\AltairSIMH>dskid.exe -type simh cpm2.dsk
cpm2.dsk:
 Driver: SIMH disc image driver
 Sidedness: 0
 Cylinders: 127
 Heads: 2
 Sectors: 32
 First sector: 0
 Sector size: 128
 Data rate: 1
 Record mode: MFM
 R/W gap: 0x2a
 Format gap: 0x52
 Drive status: 0x28
 Filesystem parameters:
 CP/M:BSH: 0x04
 CP/M:BLM: 0x0f
 CP/M:EXM: 0x00
 CP/M:DSM: 0x1ef
 CP/M:DRM: 0xff
 CP/M:AL0: 0xf0
 CP/M:AL1: 0x00
 CP/M:CKS: 0x40
 CP/M:OFF: 0x06
d:\user\pohlers\AltairSIMH>dskutil.exe -type simh cpm2.dsk
LibDsk Disk Utility v1.3.5
:#
Statistics for cpm2.dsk:
Cylinders: 127 7f
Heads: 2 02
Tracks: 254 fe
Sec/cyl: 32 20
Sec/track: 64 40
1st sec: 0 00
Sec size: 128 0080
Data rate: 300
Encoding: MFM
:$
sides=0
cylinders=127
heads=2
sectors=32
secbase=0
secsize=128
datarate=DD (300 kbit)
rwgap=2a
fmtgap=52
fm=N
nomulti=N
noskip=N
cpmtools: libdsk-Type "simh" ist wichtig!
cpmls -f simh -T simh cpm22.dsk