+
+
+
+
+
+
|
- - + Back to the index
-
-However, if you think that you can port an operating system -to, say, the Silicon Graphics machine mode of GXemul and hope that your -operating system will run on a real SGI machine, then you will most -likely fail. GXemul simply does not emulate things well enough for that to work. -Another example would be specific CPU details; if your code depends on, -say, R10000 specifics, chances are that GXemul will not be sufficient. - -
-In many cases, hardware devices in GXemul are only implemented well -enough to fool eg. NetBSD that they are working correctly, while in -fact they don't work very much at all. Please keep this in mind, if you plan -to use GXemul when porting your code to MIPS. +
Some examples of things that don't work, that you should keep in +mind: +
+
+
+
+
The bottom line is that GXemul can be useful as yet another way to test +your code during development, but it should not be fully relied on. @@ -158,7 +180,7 @@ Here are some examples. If you want to run a NetBSD/pmax kernel on an emulated DECstation machine, you would use a command line such as this:
- $ gxemul -E dec -e 3max -b -d pmax_diskimage.fs netbsd-pmax-INSTALL + $ gxemul -e 3max -d pmax_diskimage.fs netbsd-pmax-INSTALL
NOTE: For some emulation modes, such as the DECstation mode, you do @@ -169,7 +191,7 @@ image is added; the first will be SCSI target 0, the second will be target 1, and so on, unless you specify explicitly which ID number the devices should have.
- $ gxemul -E dec -e 3max -b -d disk0.raw -d disk1.raw -d 5:disk2.raw netbsd-pmax-INSTALL + $ gxemul -e 3max -d disk0.raw -d disk1.raw -d 5:disk2.raw netbsd-pmax-INSTALLNote: In the example above, disk2.raw will get scsi id 5.
@@ -178,17 +200,17 @@ For example, the following command would start the emulator with two CDROM images, and one harddisk image:
- $ gxemul -E dec -e 3max -b -d image.iso -d disk0.img -d c:second_cdrom.img netbsd-pmax-INSTALL + $ gxemul -e 3max -d image.iso -d disk0.img -d c:second_cdrom.img netbsd-pmax-INSTALLUsually, the device with the lowest id becomes the boot device. To override this, add a 'b' prefix to one of the devices:
- $ gxemul -E dec -e 3max -b -d rootdisk.img -d bc:install-cd.iso name_of_kernel + $ gxemul -e 3max -d rootdisk.img -d bc:install-cd.iso name_of_kernelIf you have a physical CD-ROM drive on the host machine, say /dev/cd0c, you can use it as a CD-ROM directly accessible from within the emulator:
- $ gxemul -E dec -e 3max -b -d rootdisk.img -d bc:/dev/cd0c name_of_kernel + $ gxemul -e 3max -d rootdisk.img -d bc:/dev/cd0c name_of_kernelIt is probably possible to use harddisks as well this way, but I would not recommend it. @@ -288,12 +310,13 @@
There is some skeleton code for running userland programs as well. This +will not emulate any particular machine, but instead try to translate +syscalls from e.g. NetBSD/pmax into the host's OS' syscalls. Right now, +this is just a proof-of-concept, to show that it could work; there's lots +of work left to do to make it actually run useful programs.
@@ -324,6 +347,7 @@ tab.csbnet.se +
- $ gxemul -E dec -e 3min -Q -M128 -q 0xbfc00000:DECstation5000_125_promdump.bin + $ gxemul -e 3min -Q -M128 -q 0xbfc00000:DECstation5000_125_promdump.bin KN02-BA V5.7e ?TFL: 3/scc/access (1:Ln1 reg-12: actual=0x00 xpctd=0x01) [KN02-BA] @@ -455,18 +480,20 @@ osconsole=3 >>-(Note: at the moment, this doesn't work. I must have broken something when -fixing something else, but this is what it looked like at the time.) -
-During bootup, the PROM complains a lot about hardware failures. + +
(Note: at the moment, this doesn't work. +I must have broken something when fixing something else, but this +is what it looked like at the time.) + +
During bootup, the PROM complains a lot about hardware failures. That's because the emulator doesn't emulate the hardware well enough yet. -
-The command line options used are: -E dec for DECstation, -e 3min for -"model 3" (5000/1xx), -Q to supress the emulator's own PROM -call emulation, -M128 for 128MB RAM (because GXemul doesn't correctly + +
The command line options used are: -e 3min for +"DECstation 3min" (5000/1xx), -Q to supress the emulator's own PROM +call emulation, -M128 for 128MB RAM (because GXemul doesn't correctly emulate memory detection well enough for the PROM to accept, so it will -always believe there is 128MB ram anyway), and -q to supress debug messages. -The 0xbfc00000 in front of the filename tells GXemul that it is a raw +always believe there is 128MB ram anyway), and -q to supress debug messages. +The 0xbfc00000 in front of the filename tells GXemul that it is a raw binary file which should be loaded at a specific virtual address. @@ -474,20 +501,53 @@
-For the O2, a suitable command to dump the prom memory range is +machines as well. I have also tried this on an SGI IP32 ("O2"), in addition +to the DECstation. + +
For the O2, a suitable command to dump the prom memory range is
>> dump -b 0xBFC00000:0xBFC80000Make sure you capture all the output (via serial console) into a file, -and then run experiments/sgiprom_to_bin on the captured file. -
-(2005-01-16: The emulator doesn't really emulate the IP32 well enough to -actually run the PROM image without using special hacks, but it might do -so some time in the future.) +and then run experiments/sgiprom_to_bin on the captured file. +
+
+
+
+
+
+
+
+
The photo on the left is from the real machine. The other two are +screenshots of the PROM running experimentally in GXemul, using -Y2 +framebuffer scaledown. + +
Normally during bootup, the IP32 PROM does a Power-On test which makes +sure that the caches and other things are working properly. GXemul doesn't +emulate all those things well enough for the tests to pass. The +experimental screenshots above were taken with cache detection skipped +manually. + +
+In other words: don't expect this to work out-of-the-box with GXemul right +now. It might work once I've added correct cache emulation. + +
The command line used to start the emulator, once correct cache +emulation has been implemented, would be something like gxemul -XQeo2 +0xbfc00000:prom.bin. + +
The same caution applies when dealing with SGI PROMs as with +DECstation PROMs: GXemul doesn't really emulate the hardware, it only +"fakes" devices well enough to fool some things, primarily NetBSD, that +it is emulating a real machine. ROM code is usually a lot more +picky about the details. + +
The graphics used in the O2 is (as far as I know) undocumented. Combining +some traces of info from how Linux/O2 draws to the screen with some +reverse-engineering of my own, I've implemented enough of the controller to +let the PROM draw rectangles and bitmaps, but not much more. The SCSI +controller is not implemented yet either.