Re-visiting Gopher on A/UX

Posted on September 13, 2021 by neozeed

Rather unintentionally some 7 years ago (to the day!) I was playing with an early gopher server on Linux, musing that one day it’d be cool to run it fully on A/UX (what is it anyways?!). And thanks to Qemu’s 68040 support the time is at hand.

First off I need to run this on Linux so I’ll need to build the appropriate branch myself. Thankfully Cat_7 has boiled it down to a really simple formula:

git clone -b q800.upstream https://www.gitlab.com/mcayland/qemu q800-upstream
cd q800-upstream
./configure --target-list=m68k-softmmu --enable-gtk --enable-sdl
make

In my case I remove the gtk and sdl as I’m running this headless.

Now onto the OS itself. While I had numerous images built over the years for Shoebill there was one major issue when compared to Qemu, and that is Shoebill loads the kernel directly while Qemu emulates the hardware so it will boot MacOS 7 directly. While on the surface this is mundane that does mean however that none of my images will actually work on Qemu as they don’t include a blessed copy of System 7. Not that I care that much I could always do a simple dump/restore [ dump.bsd 0f – /dev/rdsk/c0d0s0 | (cd /mnt; restore xf -) ] of my A/UX stuff that I care about anyways. Luckily since I had added that SCSI file support to Cockatrice I could still partition out some disks and install from there.

Now for the further bit of bad news for me is that I found that the 68020 based Shoebill ran 3.0.0 far more stable than 3.0.1 or 3.1. So I’d built everything around 3.0.0. And of course trying to boot 3.0.0 on a Quadra 800 just gives you a hard lock up. I don’t have the setup disk for 3.0.0 but mounting the CD-ROM gives you access to the disk tool (the 3.0.0 version doesn’t check for the Apple string on SCSI ROMS so you can partition with that as well). Anyways too much time thinking I’d done something wrong until this had to be pointed out to me:

That’s right, 3.0.0 doesn’t run on the Quadra 800. Much longer ago I had a Quadra 950, fantastic beast of a machine, and yes it ran 3.0.0 just great. So shockingly running the right versions got me up to a working system just fine.

Now of course back in the Shoebill days I got ‘3.0.1’ kind of working by cheating. The /mac programs didn’t work on Shoebill however I could copy them over from 3.0.0 to get a working system. Could I substitute a 3.0.1 kernel & /mac directory onto a 3.0.0 system?

So first up the System 7 install from A/UX 3.0.0 is too old for a Quadra 800. Obviously just use the one from 3.0.1. Great.

This lead to a problem where the root filesystem always needs to be checked in single user mode. Something that is shockingly hard to do when your Quadra runs so fast as you have less than a second to hit the ‘top’ button to halt the autoload.

Naturally the standalone runs fine, with no errors.

Thinking that it’s the start-up scripts I remove all the fsck’s and then get this message:

Great a kernel panic. ialloc: dup alloc. Thinking that maybe it’s confusing the UFS, I go ahead and format the disk in SYSV and restore the image onto that.

This gets me another kernel panic, this time no root filesystem. Surprise the SYSV filesystem was made optional in a default install. I run ‘newconfig sysv’ from 3.0.1 and copy that kernel back, and for good measure the shared libraries from 3.0.1. Now I get a different error:

Interesting, I try to hit restart, and instead I get dumped into text mode!

So here we are a 3.0.1 kernel with a 3.0.0 userland! I’m going to use this as a server anyways so I don’t really care about the Mac UI. Naturally so many twists and turns I’ll just skip to the end. Networking didn’t work correctly. Maybe I should have copied all the network stuff from 3.0.1 over but at this point it’s basically a 3.0.1 system so why even bother?

So the next thing of course is just to setup Qemu to listen on a loopback and add some disks. A lot of disks.

./qemu-system-m68k \
-L pc-bios \
-m 256 \
-M q800 \
-vnc 10.11.0.1:35 \
-serial stdio \
-bios Quadra800.rom \
-net nic,model=dp83932,netdev=ne -netdev user,id=ne,hostfwd=tcp:10.11.0.1:42323-:23,hostfwd=tcp:10.11.0.1:40070-:70,hostfwd=tcp:10.11.0.1:40080-:80 \
-drive file=pram-aux.img,format=raw,if=mtd \
-device scsi-hd,scsi-id=0,drive=hd0,vendor="SEAGATE",product="ST225N",ver="1.0" \
-drive file=scsi0.vmdk,media=disk,format=vmdk,if=none,id=hd0 \
-device scsi-hd,scsi-id=1,drive=hd1,vendor="SEAGATE",product="ST225N",ver="1.1" \
-drive file=scsi1.vmdk,media=disk,format=vmdk,if=none,id=hd1 \
-device scsi-hd,scsi-id=2,drive=hd2,vendor="SEAGATE",product="ST225N",ver="1.2" \
-drive file=scsi2.vmdk,media=disk,format=vmdk,if=none,id=hd2 \
-device scsi-hd,scsi-id=3,drive=hd3,vendor="SEAGATE",product="ST225N",ver="1.3" \
-drive file=scsi3.vmdk,media=disk,format=vmdk,if=none,id=hd3 \
-device scsi-hd,scsi-id=4,drive=hd4,vendor="SEAGATE",product="ST225N",ver="1.4" \
-drive file=scsi4.vmdk,media=disk,format=vmdk,if=none,id=hd4 \
-device scsi-hd,scsi-id=5,drive=hd5,vendor="SEAGATE",product="ST225N",ver="1.5" \
-drive file=scsi5.vmdk,media=disk,format=vmdk,if=none,id=hd5 \
-device scsi-hd,scsi-id=6,drive=hd6,vendor="SEAGATE",product="ST225N",ver="1.6" \
-drive file=scsi6.vmdk,media=disk,format=vmdk,if=none,id=hd6

One nice thing is that since we are on Qemu I don’t have to use raw disk images, I can zero stuff out and use VMDK’s. Nice. I guess I could bridge the VM later, but for now NAT is fine enough as all I need is telnet & gopher. So I grab gopher2_3.1.tar.gz, rebuild and move over my gopher site from Linux into A/UX and I’m up and running in no time. It was shockingly easy. I update a few things to reflect it running on A/UX now.

And just like that I took my semi popular gopher site, and moved it to A/UX seven years after thinking that this would be a ‘good idea(tm)’. I’m sure it won’t backfire spectacularly.

I don’t know if any of this is useful or interesting but it was to me. It’s been nice that Qemu has been able to keep uptime in several days, I had 3 days of uptime before I took it down to max out the storage so I could possibly do more with it.

Naturally it’s still available as gopher://gopher.superglobalmegacorp.com

Qemu’s Macintosh Quadra in alpha usability! (runs A/UX!)

Posted on September 2, 2021 by neozeed

I’m being a bit unfair as far as Alpha’s go it’s rough to get going but wow it’s GREAT! For starters it’s a Quadra 800 so System 7.1 through 8.1 will work. Also this has full 68040 capabilities so yes that means MMU and YES A/UX (and NetBSD!) will run

As always you can find more on emaculation, the best source for news and info on emulating the Mac.

Additionally you can find the setup guide here.

Many of my Shoebill/Cockatrice III images didn’t work at all. Some at least were picked up as blank disks. I had less luck with freshly created raw/vmdk or qcow2 disks. Not sure at all. My minimal 7 2gb disk worked fine as a donor, and even converting to a vmdk was fine. Sooo YMMV. But hey it’s an Alpha and YES IT CAN WORK.

Another plus is that the idle loop works fine so it won’t burn 100% of your CPU. This could possibly be a great gopher server!? Time will tell.

Installing Debian Linux 5.0 on the Qemu Dec Alpha

Posted on August 10, 2021 by neozeed

Years ago I’d written this terribly vague, and generic quickie post that Debian 5 will in fact boot inside of Qemu. I didn’t really want to get into it as it’s a little complicated and a lot painful. People have cried out over the years, but I figured I’d help people.

For operating system tourists, I’ll save you the story, just go here, and download qemu-2.2.50-DecAlphaDebian.7z. You’ll quickly find out it’s borderline useless, and go onto your next thing. You’re welcome.

First thing this was running in 2014, and newer Qemu’s seem to behave… strange. So I stuck with a late 2014 build of Qemu. If you deviate from here , you are on your own. I did dig up quite a few other ~~Dec Alpha AXP emulators and put them on archive.org~~. -But that’s totally up to you, again I’m sticking with 2014’s Qemu.

The BIOS/Pal on Qemu’s Alpha is far from complete and cannot read disks, so no boot sectors, boot loaders, no on disk kernels. All is not lost, you can inject a kernel and initrd, however this is where the fun is. Obviously to install you need to extract both from the ISO file. Also make sure the kernel is decompressed, add a .gz extension and de-compress it, as it should be around 6MB.

qemu-system-alpha.exe -net nic -net user -drive file=alpha.vmdk,if=ide,media=disk -drive file=debian-5010-alpha-netinst.iso,if=ide,media=cdrom -initrd initrd.gz -kernel vmlinux

This is vaguely how to boot up the installer. Partition, make sure hda1 hda2 hda3 etc are created and all is fine.

Now the next amount of fun is that you need to extract the created initrd as the installer initrd always launches the installer. The busybox cannot create tar files, there is no ftp or scp, also I couldn’t get it to even try to mount NFS images.

However on Windows 10 with WSLv2 or a Linux machine you can mount the disk image (keep it raw? or convert it?)

losetup /dev/loop0 myimage.disk 
partprobe /dev/loop0
mount /dev/loop0p1 /mnt/myimage

These three steps will let you mount the disk in this case /dev/loop0p2 which is the root filesystem. Debian didn’t have partprobe installed so I had to apt-get install parted

Now that you can mount it, you can copy the boot/initrd.img-2.6.26-2-alpha-generic file.

We do need to tell Linux where the root filesystem is so to finally run Qemu it’s like this:

qemu-system-alpha.exe -net nic -net user -drive file=alpha.vmdk,if=ide,media=disk -initrd initrd.img-2.6.26-2-alpha-generic -kernel vmlinuz-2.6.26-2-alpha-generic -append "root=/dev/hda2"

Obviously this was a lot more time consuming than it should be, but now I can do useful things.

Also sometimes Qemu just sits there with a black screen. the UI is waiting for something ,not sure what. It’ll either come to life on it’s own or you got to bang it.

Using Qemu in 2020

Posted on July 31, 2020 by neozeed

So I wanted to dive back into old BSD, and I wanted to use the new native Qemu on OS X. That means having to “learn” the new crazy syntax that has drifted a LOT over the last 10+ years.

I want to run NetBSD 1.0 and tear into the GCC 2.x patches required back in the day

In the old days, I was using Qemu 0.13 and had it working using the following:

qemu.exe -L pc-bios -hda netbsd-1.0.vmdk -net nic,model=ne2k_isa -net user -redir tcp:42323::23 -m 64 -no-rebootÂ  -rtc base=localtime -k en-us

Thankfully I was using VMDK containers, probably as I’m sure I installed it under VMware, with it’s better floppy support, but pulled it back to Qemu to have NE2000 support. Now let’s look at the dmesg to where the source of the problem is, the network card:

NetBSD 1.0 (QEMU) #0: Thu Sep 22 06:45:37 PDT 2016
Â  Â  [email protected]:/usr/src/sys/arch/i386/compile/QEMU
CPU: Pentium (GenuineIntel 586-class CPU)
real memÂ  = 67764224
avail mem = 62312448
using 852 buffers containing 3489792 bytes of memory
pc0 at isa0 port 0x60-0x6f irq 1: color
com0 at isa0 port 0x3f8-0x3ff irq 4: ns16550a, working fifo
lpt0 at isa0 port 0x378-0x37f irq 7
wdc0 at isa0 port 0x1f0-0x1f7 irq 14
wd0 at wdc0 drive 0: 1023MB 2080 cyl, 16 head, 63 sec <QEMU HARDDISK>
fdc0 at isa0 port 0x3f0-0x3f7 irq 6 drq 2
fd0 at fdc0 drive 1: density unknown
pci0 at isa0 port 0x0-0x665: configuration mode 1
pci0 bus 0 device 0: identifier 12378086 class 06000002 not configured
pci0 bus 0 device 1: identifier 70008086 class 06010000 not configured
pci0 bus 0 device 2: identifier 11111234 class 03000002 not configured
ed0 at isa0 port 0x320-0x33f irq 10: address 52:54:00:12:34:56, type NE2000 (16-bit)
npx0 at isa0 port 0xf0-0xff: using exception 16
biomask 4040 netmask 412 ttymask 12
changing root device to wd0a

So the important thing here is that the NE2000 is the ed0 device using an IO of 0x320 and IRQ 10. I’m pretty sure back then I cheated, and just recompiled Qemu to remove the default definition that doesn’t work properly with trying to share IRQ 9.

Keeping this in mind, let’s build this for the new Qemu:

qemu-system-i386 -net none -device ne2k_isa,iobase=0x320,irq=10,netdev=ne -netdev user,id=ne,hostfwd=tcp::42323-:23 -drive file=netbsd-1.0.vmdk,if=ide,index=0,media=disk,cache=writeback,format=vmdk -rtc base=localtime -k en-us

So the first important thing is to disable any/all defualt NIC’s with the ‘net none’ flag. Next to add in the NE2K_ISA type device manually so I can specify the iobase & irq manually. Note the netdev as this is used to tie in the emulated device, to the backend that will process the packets. The next part is the redirect to have the host listen on port 42323 and redirect them into port 23 of the VM. Again the syntax to redirect ports has drifted significantly. The hostfwd now is bound directly to the netdev user, in this new syntax it allows for multiple NIC’s to be bound to multiple user NAT’s if needed.

-device ne2k_isa,iobase=0x320,irq=10,netdev=ne -netdev user,id=ne,hostfwd=tcp::42323-:23

The next ting is the hard disk, before ‘hda’ worked fine, although like everything else that is subject to change in the future, so dealing with it now, use the drive flag:

-drive file=netbsd-1.0.vmdk,if=ide,index=0,media=disk,cache=writeback,format=vmdk

It could be my personal opinion but the drive syntax, although much longer is easier to work with. The key parts being what interface to use (IDE), and what port/index to plug the device in (0), along with the media type, the cache strategy, along with the encoded format, which is more so important when dealign with RAW devices, as unidentified media will be tagged as raw, however it’ll be mounted read-only unless it is directly specified as above.

For additional fun, the serial port can be set to a MS Mouse port, although I haven’t tested it as of yet.

-serial msmouse

Have fun QEMU’ing!

Qemu 5 was recently released

Posted on May 4, 2020 by neozeed

It’s been jumping numbers like crazy, and I’m still holding onto 0.9 because I’m weird. Anyways there is something amazing hiding in all those release notes and stuff:

The m68k emulation is good enough to run Linux! Granted the target machine is the Macintosh 800, although the Mac ROM doesn’t boot enough to do anything Apple enough, using a serial console however does get us into the system. On my ancient Mac Pro I get emulation in the speed range of a 1Ghz G4!

root@qemu68k:~# cat /proc/cpuinfoÂ 
CPU: 68040
MMU: 68040
FPU: 68040
Clocking: 1304.9MHz
BogoMips: 869.99
Calibration: 4349952 loops

Absolutely amazing!

Installation is a bit tricky as there is no true bootrom / boot process, so I had to load the installer with a dummy ‘raw’ disk, and tar the kernel & initrd to that raw disk so I could later extract it on the native OS to boot into the disk. I followed mostly the instructions here.

And what is that? NeXT CUBE emulation?

The peripherals are nowhere near complete enough to boot, HOWEVER it does boot the PROM, complete with keyboard support.

qemu-system-m68k -M next-cube -bios Rev_2.5_v66.BIN

It’s fun enough to play with. And thanks to Qemu’s fast emulation, perhaps this is a speedy way to run stuff in the future?

Now isn’t that cool?

How not to store optical media

Posted on August 19, 2019 by neozeed

Or how I finally broke down and bought that MkLinux book after all these decades. When I did own a PowerPC Mac as my daily driver it was an iMac back in 1999 and I ran OS X Server. I later bought a G4 to only find out that OS X didn’t support the G4. Linux had issues too and I ended up running OpenBSD on the G4. Which was fun, although for the ‘work at home’ bit, I ended up needing Windows NT 4.0, so I ran that in OS 8 on SoftPC. Yay.

I didn’t have any luck with Linux on Power as MkLinux wanted the beige hardware, and by the time I felt like digging in again to Linux, OS X had finally been ported to the G4 Sawtooth’s so it really didn’t matter.

I’d seen this book in a store but it was pretty expensive, and geared to such a tiny market. Although Mach does compile on the i386, why they didn’t include it was well to push Mach/Linux as a platform well that’s beyond me. Then again looking at the stunning success of Darwin on i386/x86_64 I guess the reality is, why bother.

I ordered this on Ebay, for the usual $5 plus $10 to ship, and it just showed up today! What mysteries lie on the CD-ROMs? I know others have posted stuff, but I wanted to hold them in my hands myself.

I didn’t know if the CD-ROM’s were included, and I first thought I got lucky: not only were they included, neither had been opened up before! These CD’s had been packed way like this for the last 22.5 years! Now for the bad part.

See that stupid leaflet in the back? Yeah well it turns out that it was a really stupid idea. No doubt this thing sat in the bottom of a stack for decades where the ink had been pressed for so long against the disk that it has transferred to the surface.

HOW ANNOYING.

So yes, they actually advertise the book, namely the one that I had bought with some crap ink leaflet in the CD-ROM pouch and it’s transferred to the disc.

Sigh.

I tried rubbing alcohol but that had no effect. I tried rubbing with a credit card, and it got a little off, but I fear I’m just going to damage the surface more.

I can only imagine what other CD-ROM’s out there that haven’t been archived are sitting under hundreds or thousands of pounds of book weight having nonsense imprinted onto them.

At least the second CD-ROM doesn’t suffer this defect and I’ll be uploading it later.

No book review yet, I’m just sitting here with this impacted CD.

UPDATE

Thanks to Shawn Novak for uploading the R3 images so I can at least pull up the compatible machines:

The latest Qemu can pull it the image fine, however trying to boot up looks like the Mach kernel just isn’t compatible enough with the emulated Mac99 machine (which isn’t surprising).

I’ll need to mess with stuff to see if the G3beige can boot Linux on Qemu, and if the BootX (I think it’s bootx?) can load the mach kernel.

Installing AIX on Qemu!

Posted on April 22, 2019 by neozeed

YES it’s real!

I’m using the Linux subystem on Windows, as it’s easier to build this Qemu tree from source. I’m using Debian, but these steps will work on other systems that use Debian as a base.

First thing first, you need to get your system with the needed pre-requisites to compile:

apt-get update;apt-get upgrade
apt-get install build-essential pkg-config libz-dev libglib2.0-dev libpixman-1-dev libfdt-dev

Great with those in place, now clone Artyom Tarasenko’s source repository

git clone --branch 40p-20190406-aix-boots --single-branch https://github.com/artyom-tarasenko/qemu.git

*NOTE from the future (2022) you may want to jump here: to check out building on newer systems. Also don’t forget about networking!

Since the frame buffer apparently isn’t quite working just yet, I configure for something more like a text mode build.

././configure --target-list=ppc-softmmu --disable-sdl --disable-vnc --disable-gtk --disable-gnutls --disable-nettle --disable-gcrypt --disable-spice --disable-numa --disable-libxml2 --disable-werror

Now for me, GCC 7 didn’t build the source cleanly. I had to make a change to the file config-host.mak and remove all references to -Werror. Also I removed the sound hooks, as we won’t need them. remove the following lines:

CONFIG_AUDIO_DRIVERS=oss
CONFIG_AUDIO_OSS=m

Now you can build Qemu. it’ll happily build in parallel so feel free to build using the -j parameter with how many cores you have. I have 32, so I use

make -j32

Okay, all being well you now have a Qemu. Now following the steps from
Artyom Tarasenko’s blog post, we can get started on the install!

First we create a 8GB disk

qemu-img create -f qcow2 aix-hdd.qcow2 8G

Next we need the custom BIOS with serial as the console.

wget https://github.com/artyom-tarasenko/openfirmware/releases/download/40p-20190413/q40pofw-serial.rom

You’ll need some AIX. I tried a 3.2.5 CD-ROM and it didn’t pick up, but AIX 4.3.3 did.

Now with all those bits in place, it’s time to run Qemu.

./ppc-softmmu/qemu-system-ppc -M 40p -bios q40pofw-serial.rom -serial telnet::4441,server -hda aix-hdd.qcow2 -vga none -nographic -net none -cdrom Volume_1.iso

Now telnet to your localhost on port 4441 and you will see the console doing it’s BIOS initialize and eventually drop to the OK prompt.

One trick I’ve found is that from the Open Firmware prompt you can find out what partitions are recognized from the firmware. If it see’s partitions then there is some hope that the image you have is valid enough to boot. In the last few days I’ve found quite a few AIX images, which are lacking the partition table, and unable to boot.

simply type in boot cdrom:2 to kick off the installer. It may take a minute or so for the installer to kick off.

If all goes well, you’ll see the BIOS reload itself, then after a minute you’ll be prompted to press 1 to select the console

It doesn’t echo, don’t panic!

Next select your language. I’m doing English.

Next it’ll ask about installation type. Default ought to be fine.

Because this will destroy the contents of the disk (which doesn’t matter as it’s blank) it’ll prompt for confirmation.

After this it’ll begin the installation. Depending on how fast your disk & CPU is this will take a while.

For me, the installation took about 11 minutes. This is using my Xeon E5-2667 v2. It took 17 minutes on my 2006 Mac Pro, with X5365’s it .

After it’s done, right around the 96% time it’ll reboot back to the BIOS

Once you are back at the OK prompt, you can now boot disk:

it’ll look like it’s hung for a minute, then it’ll start booting from disk!

Once the OS is booted up, you select the terminal type. I’m using putty but I’ll select the vt100. Of note the function keys are selected by hitting escape and then the number key. So F3 is ESC 3.

I’m just going to finish the install, as we can always run smitty to mess with the system more, but right now I’m just interested in a base install of the BOS (Base Operating System, and IBM ISM).

A few moments later, you’ll get dumped to the login prompt.

By default there is no password, so just login as root, and there you go, your very own virtual AIX 4.3 system.

# uname -a
AIX localhost 3 4 000000004C00

So there you go! All thanks to Artyom’s hard work!

Added UDP to Qemu0.90

Posted on March 18, 2019 by neozeed

Yes, I know it’s kinda pointless as it’s horribly out of date, but I’m still having fun. Anyways now it’ll integrate with dynamips!

So yeah, in this example, instead of the usual “-net user” and the built in SLiRP stack, this uses UDP to talk to a stand-alone SLiRP stack. This will let you plug your Qemu into virtual Ethernet switches/hubs and interfaces of virtual routers. Even mixing and matching connections to different emulators that use UDP to exchange packets.

In this case I have a VMDK loaded with a NE2K-PCI driver, and QuakeWorld for MS-DOS. I also made the MPU401 external although it’s hanging on a secondary flag…

qemu.exe -L pc-bios -m 64 -soundhw sb16,adlib -mpu401 xx -net nic,model=ne2k_pci -net socket,udp=127.0.0.1:4000,remote=127.0.0.1:4001 -hda qworld.vmdk

This has the Qemu instance listen on UDP port 4000, and connect to the same physical host on port 4001.

The recipical for the SLiRP stack from my bashed Dynamips is:

slirp_rdr.exe 4001 127.0.0.1 4000

Which in this case listens on port 4001, and connects back on port 4000.

Hopefully it makes some sense to someone.

Download it, if you want!

Degrading qemu performance in DooM Part II

Posted on March 15, 2019 by neozeed

ticks for demo (fewer is better)

Version	ASM FixedDiv/FixedMul	C
0.9.0	259	268
0.10.5	299	300
0.11.0	316	317
0.12.0	289	281
0.12.5	290	282
0.14.0	282	274
0.14.1	280	269
20180430	192	195
20190218	187	187

So after the last round, I went ahead and dug out my crap version, where I had just recently found a nice abs() fix for a FixedDiv issue that the old iD code suffers from, and re-built a version of DooM that both used the assembly fixed division, and another with the C version. To compile I used my old GCC 2.7.2.3 to build with the flags:

-m486 -msoft-float -ffast-math -O2 -fforce-addr -fomit-frame-pointer

So here we go using the versions of Qemu that I can build quickly with GCC 3.4.5 MinGW, along with the last two pre-built Win64 builds.

It’s kind of interesting just how close the performance is between the two versions.

Naturally the real test is to run it on actual hardware, and to try a few versions of Watcom C.

Maybe the real takeaway is that Qemu runs GCC built code better…?

Adding DOSBox’s MPU401 to Qemu 0.90

Posted on March 14, 2019 by neozeed

I thought this may be something cool, if not kind of pointless. Anyways the MPU401 UART can be run like a traditional serial port with an IRQ, in intelligent mode, or just as a ‘dumb’ device you can just bit bang to talk to MIDI devices. So while playing with DOSBox I thought it’d be fun to take it’s emulation and plug it into Qemu.

And this is the end result.

It’s far from perfect, when it works it does tend to work well, although it fails to work with things like Return to Zork, but it does work with DMX’s sound code in DooM and the MPU401 driver for Windows 3.1

While doing this I was originally struggling with mapping the IO ports. Qemu has some functions to map in the memory model to assign a function that will trap read/write space. In this case base is 0x330 the base of the MPU401 device.

register_ioport_write(base, 8, 1, mpu401_ioport_write, s); register_ioport_read(base, 8, 1, mpu401_ioport_read, s);

I was thinking that the port 0x331 needed to be mapped in the same way, but it turns out after looking through more of the source, it’s actually a word aligned access. So in that case you can use a switch to see which port is actually being accessed.

static uint32_t mpu401_ioport_read(void *opaque, uint32_t addr) {
switch(addr&0xf)
{
case 0:
return(MPU401_ReadData(addr,0)); break;
case 1:
return(MPU401_ReadStatus(addr,0)); break;
default:
return(0xff); break;
}
return(0xff);
}

Pretty simple, right?

And from there it’s a matter of mapping the DOSBox MPU code, along with the Windows interface code. Since I’m not using intelligent or IRQ mode, I just amputated the code where applicable.

If anyone wants to look at what I did to merge into anything else (and probably do a better job!) it’s on sourceforge as mpu401.c.

Otherwise the binary is available on sourceforge:

Virtually Fun

Fun with Virtualization

Category Archives: QEMU