Making bootable ISO images

I know for most people using mkisofs is second nature, but I needed to get a machine running MS-DOS without floppies… and it had to be on the bare metal.. Oh joy.

Now I’ve kind of done this before but I’ve never gotten it to preserve the directory structure.  It seems that it’s important to specify some output…

The ‘fun’ thing is that I was able to use virtual pc to build the boot diskette with IDE cdrom drivers, and make sure it works in that it mounted the CD and set the path there…

So I have extracted my MS-DOS install from the floppies into a directory on my pc and I keep the file dos622_1.img in the same directory so mkisofs can place it in the image.  Then it’s just a matter of running:

..\mkisofs.exe -o ..\x.iso -J -r -v -V test_disk -b dos622_1.img .

And I get an x.iso that can boot MS-DOS, and has all the dos commands in place, I can partition & format the hard disk and copy DOS into place.

It’s not much to see, but if you need legacy stuff it’ll be a life saver.. and I know I’ll end up losing the flags and needing them again!


While I was looking around at fleshing some stuff out on gunkies I came across this little nugget of MS-DOS history.

You can actually download 86-DOS the precursor to MS-DOS!  And it even includes a bunch of SOURCE CODE!  The best part is the awesome emulation suite SIMH can run 86-DOS!

Ok, for the first part of this, I thought I’d try my MS-DOS build of SIMH 3.81 which can be found on the sourceforge pages here.  Because I’m using a 64bit OS there is no 16bit environment to kick start DPMI stuff, so I’m using the most excellent DOSBox emulator.

Thanks to the hard work of Peter Schorn, you can download the run able image for 86-dos right here, then simply point the Altair z80 emulator from SIMH to it, and you’ll be running in no time.

To run it, simply point the z80 emulator to the boostrap file 86dos.  Then just follow the onscreen prompts.


Then you’ll be up & running!  Notice how the prompt is different from MS-DOS, and yet how familiar it ‘feels’.  Also check out the commands!


Rumor has it that edlin has largely remained the same, up to TODAY on 32 bit versions of Vista!  I haven’t even verified it, but it would prove interesting.

I should also point out that Peter has amassed quite the collection of CP/M images, programming languages and other interesting stuff here.

new MS-DOS build of SIMH 3.8-1

Well I went ahead and cranked out another copy of the SIMH for MS-DOS package, which includes a new emulator this time around, the SWTPc 6800. It includes a disk image for Flex 2.0, and I’ve also switched the DOS extender from DOS4G/W to DOS-32A.

You can download it here:

Minor SIMH fun

Well I updated the packages for SIMH last night, and I’ve included the win32s stuff and MS-DOS builds. This ought to allow some old schoole to have some fun!

The packages should be visable from here:

I have also decided that the MS-DOS version (being the lowest common denominator) should include some kind of ‘sampler’ of OS’s so that you can see right out of the gate what simh is capable of. Naturally you can download the MS-DOS version, and simply replace the exe’s with stuff for windows/win32s/linux etc..

SIMH 3.8-0 for MS-DOS

This is a quick survey of SIMH 3.8-0 for MS-DOS. I’ve built these exe’s with Watcom C++ 11.0a.

You can break out of any of the simulators by pressing CONTROL+E.

All of the EXE’s are for the MS-DOS environment, and I’ve built them with DOS/4GW in mind. I will have to say that an initial test shows that running this stuff under a DPMI server like Windows or OS/2 provides better performance then native switching.. It could be my PC, however I’d recommend anyone who uses these EXE’s to try them natively and under Windows 3.1 at a minimum.. Because all of the MS-DOS nature of these programs, no disk files can be over 2 gigabytes. I don’t know if that’ll be an issue but of course you can have multiple files/partitions as I recall MS-DOS 5 having a 2 gigabyte file/partition size limit..

For anyone running this natively I have included only one copy of dos4gw.exe in the root of the zip.

1. Altair
2. Altair Z80
3. The HP2100
4. The Interdata 32b
5. The Nova
6. The PDP-11
7. The PDP-8
8. The MicroVAX II
9. The VAX 11/780

1. Altair 8800

This is the Altair 8800 emulator with both AltairDOS and CP/M 2.2

Both CP/M and Altair DOS are from the file


C:\simh\altair\work>altair.exe altdos.ini
DOS/4GW Protected Mode Run-time Version 1.97
Copyright (c) Rational Systems, Inc. 1990-1994

Altair 8800 simulator V3.8-0


——8<------8<------8<------8<------8<------8< cpm.bat ——8<------8<------8<------8<------8<------8<
C:\simh\altair\work>altair.exe cpm22.ini
DOS/4GW Protected Mode Run-time Version 1.97
Copyright (c) Rational Systems, Inc. 1990-1994

Altair 8800 simulator V3.8-0
62K CP/M VERSION 2.2 (ALTAIR 8800)
Simulation stopped, PC: 172052 (JNC 172047)
sim> q
——8<------8<------8<------8<------8<------8< ============================
2. The Altair 8800 z80 emulator.

This is more full featured then the other Altair emulator, and I’ve found the z80 to have more
software available. I’ve included the CP/M 2.2 that I found


C:\simh\altairz8\work>altairz8.exe cpm2.ini
DOS/4GW Protected Mode Run-time Version 1.97
Copyright (c) Rational Systems, Inc. 1990-1994

Altair 8800 (Z80) simulator V3.8-0

64K CP/M Version 2.2 (SIMH ALTAIR 8800, BIOS V1.25, 2 HD, 15-Jan-07)

Simulation stopped, PC: 0F3FA (RRA)
sim> q
——8<------8<------8<------8<------8<------8< ============================
3. The HP2100 emulator.

I really don’t know much about this machine, but I included a way to run the basic1 program I
found online. It kind of reminds me of the ROMBASIC back ‘in the day’… It’s basic with line
numbers so I know it’s kind of old.. I really don’t know much otherwise about this machine.


C:\simh\hp2100\work>hp2100.exe basic1.ini
DOS/4GW Protected Mode Run-time Version 1.97
Copyright (c) Rational Systems, Inc. 1990-1994

HP 2100 simulator V3.8-0


Simulation stopped, P: 17436 (JMP 17435)
sim> q
4. The Interdata 32b emulator


Both of these unix’s were taken from the files and respectively.

This is research Unix v6 ported to the Interdata. I set the batch file to tell you how to
bootstrap the system, as it doesn’t just ‘turn on’.. Otherwise it should be comparable to Unix v6 on the PDP-11 or any other v6. This should be the first port of Unix outside of Western Electric. There is no halt/reboot/init 0, so I just sync the disk a few times, and then interrupt the emulator and quit.

C:\simh\id32\unix6>id32.exe v6.ini
DOS/4GW Protected Mode Run-time Version 1.97
Copyright (c) Rational Systems, Inc. 1990-1994

Interdata 32b simulator V3.8-0
at the ? prompt type in:
DOS/4GW Protected Mode Run-time Version 1.97
Copyright (c) Rational Systems, Inc. 1990-1994

Interdata 32b simulator V3.8-0
v6.ini> d lfc tps 100
Read only argument
Memory = 182.50 K

login: root
You have mail.
# sync
# sync
# sync
Simulation stopped, PC: 2EB5C (EPSR R1,R0)
sim> q

This pretty much follows in the steps of the Unix v6 above. This is the research version of UNIX v7.

At the : prompt type in
ECHO is off.
Then at the # prompt hit CONTROL+D
the root password is root
DOS/4GW Protected Mode Run-time Version 1.97
Copyright (c) Rational Systems, Inc. 1990-1994

Interdata 32b simulator V3.8-0

: dsk(1,0)unix
Memory = 248.0 K
# Restricted rights: Use, duplication, or disclosure is subject
to restrictions stated in your contracts with Western Electric
Company, Inc. and the University of Wollongong.
Fri Jan 2 18:15:04 EST 1970

login: root
# sync
# sync
# sync
Simulation stopped, PC: 00D20 (EPSR R1,R0)
sim> q
——8<------8<------8<------8<------8<------8< ============================
5. The Nova emulator


This is RDOS V7.50, which I honestly don’t know anything about… I retrieved this OS from the archive rdosswre.tgz .


C:\simh\nova\work>nova.exe rdos.ini
DOS/4GW Protected Mode Run-time Version 1.97
Copyright (c) Rational Systems, Inc. 1990-1994

NOVA simulator V3.8-0


NOVA RDOS Rev 7.50
Date (m/d/y) ? 10/31/77
Time (h:m:s) ? 10:10:00

6. The PDP-11 Emulator


This is the Unix v1 restoration project’s latest disk image, that I have retrieved from
Being one of the first versions of Unix it’s super primitive, however I thought it was interesting to include in this SIMH sampler to see just how far UNIX has progressed, and just how much is the same.


C:\simh\pdp11\unixv1>pdp11 simh.cfg
DOS/4GW Protected Mode Run-time Version 1.97
Copyright (c) Rational Systems, Inc. 1990-1994

PDP-11 simulator V3.8-0
Disabling CR
Disabling XQ
RF: buffering file in memory
TC0: 16b format, buffering file in memory
simh.cfg> att dci 5555
File open error

:login: root
Simulation stopped, PC: 007332 (MOV (SP)+,25244)
sim> q
RF: writing buffer to file
7. The PDP-8 Emulator


This is the PDP-8 emulator with OS8. I really don’t know anything about this other then the
‘list’ command… I retrieved this from the file os8swre.tgz .


C:\simh\pdp8\work>pdp8 os8.ini
DOS/4GW Protected Mode Run-time Version 1.97
Copyright (c) Rational Systems, Inc. 1990-1994

PDP-8 simulator V3.8-0
RX: buffering file in memory

8. The MicroVAX II Emulator


This is the MicroVAX II emulator with a miniroot of Quasijarus 0c. It’s not exactly fully functional in this state, but it’s enough to exercise the emulator, and boot up from disk.
I’ve configured the NVram so it will just boot up by default. I have left the installation tape image as quas.tap. Please note that this is *NOT* enough for a full install, this is just a demo to check that your system works.


C:\simh\vax\quas>vax.exe quas.ini
DOS/4GW Protected Mode Run-time Version 1.97
Copyright (c) Rational Systems, Inc. 1990-1994

VAX simulator V3.8-0
NVR: buffering file in memory
Loading boot code from ka655x.bin

KA655-B V5.3, VMB 2.7
Performing normal system tests.
Tests completed.
Loading system software.


loading boot

: /vmunix
326312+104440+130352 start 0x23b8
4.3 BSD Quasijarus UNIX #3: Sat Feb 14 20:31:03 PST 2004
[email protected]:/nbsd/usr/src/sys/GENERIC
real mem = 33521664
SYSPTSIZE limits number of buffers to 80
avail mem = 31697920
using 80 buffers containing 655360 bytes of memory
MicroVAX 3000, ucode rev 6
uda0 at uba0 csr 172150 vec 774, ipl 15
uda0: version 3 model 3
uda0: DMA burst size set to 4
ra0 at uda0 slave 0: ra81, size = 891072 sectors
dz0 at uba0 csr 160100 vec 300, ipl 15
dz1 at uba0 csr 160110 vec 310, ipl 15
dz2 at uba0 csr 160120 vec 320, ipl 15
dz3 at uba0 csr 160130 vec 330, ipl 15
Changing root device to ra0a
Automatic reboot in progress…
Tue Feb 3 17:52:10 PST 2004
Can’t open checklist file: /etc/fstab
Automatic reboot failed… help!
erase ^?, kill ^U, intr ^C
# sync
# sync
# sync
Simulation stopped, PC: 800029AF (BNEQ 800029C6)
NVR: writing buffer to file
9. The VAX 11/780 Emulator


The VAX 11/780 is a bit weird in that it cannot run it’s vmb.exe directly, unlike how the
MicrovaxII can run its ROM. I’ve been using extracted boot code to get the 11/780 to run. Again because I’m more familiar with Unix, I chose to include BSD 4.2’s miniroot to test functionality. This is really only suitable for testing the emulator out. I extracted the file bootra from the source code, and I took the miniroot file from the tape.


C:\simh\vax780\work>vax780.exe bsd42.ini
DOS/4GW Protected Mode Run-time Version 1.97
Copyright (c) Rational Systems, Inc. 1990-1994

VAX780 simulator V3.8-0
loading ra(0,0)boot
: ra(0,0)vmunix
4.2 BSD UNIX #9: Wed Nov 2 16:00:29 PST 1983
real mem = 8384512
avail mem = 7073792
using 102 buffers containing 835584 bytes of memory
mcr0 at tr1
mcr1 at tr2
uba0 at tr3
hk0 at uba0 csr 177440 vec 210, ipl 15
rk0 at hk0 slave 0
rk1 at hk0 slave 1
uda0 at uba0 csr 172150 vec 774, ipl 15
ra0 at uda0 slave 0
ra1 at uda0 slave 1
zs0 at uba0 csr 172520 vec 224, ipl 15
ts0 at zs0 slave 0
dz0 at uba0 csr 160100 vec 300, ipl 15
dz1 at uba0 csr 160110 vec 310, ipl 15
dz2 at uba0 csr 160120 vec 320, ipl 15
dz3 at uba0 csr 160130 vec 330, ipl 15
root on ra0
WARNING: should run interleaved swap with >= 2Mb
erase ^?, kill ^U, intr ^C
# sync
# sync
# sync
Simulation stopped, PC: 8000162E (BRB 80001620)
——8<------8<------8<------8<------8<------8< The entire source is in the ‘source’ directory with projects for all of the SIMH material.
There are a few emulators that *WILL NOT BUILD* for MS-DOS because of a lack of 64bit integers. I suppose if there is any call for the missing emulators with the DJGPP compiler, assuming that it contains 64bit integer support. It’s completely unverified on my part. I’ve also done some preliminary work on networking with packet network drivers, however I am experiencing some weird timeouts. It’s hard to track down at the moment, but I’ll keep plugging away.

I don’t think there is any reason why you would not be able to use OpenWATCOM to build these files.

Some fun networking with MS-DOS & Novell Netware.

Ok I wanted to do this eventually but now I’ve finally done it. I have constructed something a little complex but it works surprisingly well.

Let me draw a picture so it’ll be a little easier to follow:

proxmox Netware diagram
proxmox Netware diagram


All of the machines in clouds are virtual…

Ok I’m going to assume you can install & configure OpenVPN on your own. I did a really simple install on Proxmox VE, just be sure to use the e1000 network adapters. All the others gave me tones of errors with any sizable traffic. Also I should point out that I’m using OpenBSD 4.3 which is the latest as of today.

dev tun0
dev-type tap
ca /etc/openvpn/ca.crt
cert /etc/openvpn/server.crt
dh /etc/openvpn/dh1024.pem
key /etc/openvpn/server.key
push “route”
push “dhcp-option DNS”
keepalive 10 120
max-clients 100
status /var/log/openvpn-status.log
verb 3
tun-mtu 1500
fragment 1300

Again I just followed the example from the OpenVPN site to set this up. What makes this different though is the fact that I’m using this in a bridge mode. As you can see I have told OpenVPN that it is to use the tun0 interface as a ‘tap’ driver.

My hostname.tun0 is this:
Link0 up

Likewise the bridgename.bridge0 is:
add em1
add tun0

And finally for this example my bridgename.em1 is:
inet NONE

So using this setup I have a ‘private’ network in which I’ve got a few virtual machines running and space for my laptop to VPN into. Now one of the virtual servers on my Proxmox server is Windows NT 4.0 Terminal Server… Yeah I know I got it cheap on ebay, and I kind of like it. Anyways I’m running Qemu on it, which is running Netware 3.12. I installed the libpcap then I had to find out what my Ethernet devices are called. I used wireshark (it was ethereal) and it’s a cool program to have around. The last version to run under Windows NT 4.0 was 0.99.4 so that’s the one I used. Once I have done this I found my device and was able to setup a string for Qemu (which was \Device\NPF_RTL80291)

Here is what I’m using:

Qemu –had netware.disk –m 16 –M isapc –L pc-bios –net nic –net pcap,devicename=”\Device\NPF_RTL80291”

This sets up an ISA computer with 16 megaybtes of ram and a single ISA nic that will utilize libpcap to send out frames on the rtl80291 that’s being emulated to my NT terminal server by proxmox.

On the ‘client’ side of things, I’m running the 64 bit version of Vista. So I’ve installed the OpenVPN that not only has 64 bit device drivers, but has a nice little GUI to connect & disconnect from the networks. Here is the OpenVPN config that is on my laptop.

dev tap
ca ca.crt
cert client1.crt
key client1.key
proto udp
remote 1194
resolv-retry infinite
tun-mtu 1500
fragment 1300

Ok, so far so good. Now I do have Virtual PC 2007 on my laptop, and I have made sure that the “Virtual Machine Network Services” were bound to the “TAP-Win32 Adapter V9” interface.

The it’s a simple matter of connecting to the VPN, then loading up the virtual PC with MS-DOS & the Novell Netware client.

Then you should be able to ‘bind’ to the server & login!

dos netware client
dos netware client

The ‘cool’ thing about this setup is that it will work over things like wifi, and easily allow you to add clients near & far. Oh and the best part for the wifi crowd is that it will use REAL encryption since WEP/WPA have all been shown to be useless. Oh yes, and it should allow you to host your DOOM, Quake 1, Rise of the Triad, Warcraft II, and Descent games…. Along with people playing at home! Using this you too can build your own IPX/Internet network!

I do hope this clears some of the uses & versility of Virtual servers, Qemu & Virtual Networking.

Back to DOS

It’s been a long while, life has been busy. But I figured I ought to try to make a post this year!

Ok, I’ve gotten a new laptop over the last few months & I’m running the 64 bit version of Vista. One or the first things us old people will find is that the MS-DOS & Win16 subsystems have been completely removed.

This of course, poses a massive problem! How to play games!!!!?

Thankfully there exists two really great solutions for Vista 64bit users. The first one I’ll suggest is Virtual PC from Microsoft, and DosBox.

It’s no wonder Microsoft has made Virtual PC a free download ( since they have crippled the compatibility of the OS. Now I’m personally a little biased for Virtual PC as I’ve been using it since it was owned by Connectix. Virtual PC is a complete PC emulation strategy, allowing you to run MS-DOS or quite a few other operating systems. For this example I’m going to install MS-DOS, but it’s capable of running all kinds of other operating systems.

Now back to my laptop. It of course doesn’t come with floppy drives, so I used an older PC with a drive to create disk images. (it was running OpenBSD so I just ran ‘dd’. Winimage is capable of creating disk images as well). Of course I could use a USB floppy drive and boot my MS-DOS 6.22 floppies from that as well.

The cool thing is that you can setup a virtual machine, boot off either real floppies or virtual disks, and you will need to setup a virtual hard disk. Naturally it will need partitioning, and formatting. As for installing games, again if you have floppies of them, everything is cool. There even is an emulated CD-ROM device, however you will need a device driver to use it! ( Virtual PC emulates an IDE CD-ROM, and you can use just about any driver you can find out there. Once you can read CD-ROM’s under the emulated MS-DOS you can install the ‘extensions’ program, which has an idle program (to stop the emulator from consuming 100% of your CPU, as MS-DOS has no inherent idle loop), and a neat program called fshare. Fshare will allow you to give your emulated PC access to a directory on the host computer.

The plus’s of Virtual PC is that it’s a more accurate emulation, it provides sound blaster pro emulation, and good psudo device emulation. The major downside for me is that it provides no joystick emulation. Of course you’ll need to bring your own DOS, however I imagine that freedos ( ought to work just fine, but I kind of like the real thing.

The second emulator I’d like to mention is DOSBox ( Unlike Virtual PC, DOSBox is not a complete system emulator, it’s designed specifically to run MS-DOS programs. So you will not need a copy of MS-DOS, nor will you need to worry about such hassles as media, or emulated hard disks.

To run DOSBox for the most part all I do is add the following lines into my config file:

Mount c: c:\Users\Jason\dos

This will make my “c” drive a dos directory in my home directory on Vista, and change the current directory there. From here I can unzip any of the old programs I have, or just copy from CD to my vista directory and just run things. Overall DOSBox has pretty good compatibility. I’ve even run Windows 3.1, and some compiler & development stuff. And yes, it supports Joysticks & the emulation of various sound cards. DOSBox also has various throttle and various video emulation strategies. The other cool thing DOSBox can do is setup a virtual IPX/SPX network, and allow you to play old DOS multiplayer games over the internet. Warcraft 2 & Doom work quite nice under DOSBox. While Virtual PC does provide virtual Ethernet interfaces, it does not provide a way to connect them up over the internet. While it could be done with loopback adapters & PPTP routing, it would be way beyond the average user. DOSBox can listen on a specified TCP port, you can setup your internet router to redirect that port to the host PC, then allow your friends to connect in.

While I can understand Microsoft’s desire to cut all ties with past OS’s in terms of support, It’s a good thing that there still exists an emulation strategy for the two of us. And between DOSBox and Virtual PC hopefully your needs will be met.

*Yes I’m aware of VMWare, however it’s not technically free, and while you can create your own config files, and disk images in Qemu, and install your own OS, it’s not the ‘right’ thing to do according to the EULA.