I'm interested in simulating the real-time experience of a Sun SparcStation 1, because I'm currently interested in RISC Workstation era at the turn of the 1990s and I've never used one. Without an actual SS1, an emulator is the easiest choice.
There are two primary emulators available. QEMU supports a SparcStation 5 emulator, but it runs as fast as possible. MAME supports SparcStation 1 emulator. It can be used to try out SunOS (e.g. version 4.1.2), but lots of things don't work, at least on the MAME Version 0.255 I'm exploring, e.g. ethernet, serial, colour framebuffers (and accelerated graphics), second drives, floppy disks, tape (I think, but I haven't tried that).
There's a fairly decent introduction to getting MAME's SS1 emulator running. The only major difference I'd make is to create an uncompressed hard disk image just using dd (which is the subject of this blog post). In my case, it's called SunHd320.hd not sunos412.chd.
dd if=/dev/zero of=SunHd320.hd bs=16k count=19530
I can then run the emulator with this command line:
./mame sun4_60 -window -slot1 "bwtwo" "-scsibus:0" harddisk "-scsibus:1" "" "-scsibus:6" cdrom -hard SunHd320.hd -cdrom SunOS_412.iso
To make it somewhat usable I needed to get data in and out, and I faffed a lot with trying to create floppy disk images or second hard disks or serial transfer, but it was basically a waste of time. I could describe my multiple attempts to use these, but suffice to say, don't go down that rabbit hole until there's good evidence they work! Then, today it occurred to me I could just use dd, which of course that Unix Workstation had in 1989 and I also have on the Mac mini 2012 I'm emulating it on.
Background: Why The SparcStation 1?
The SparcStation 1 is a really interesting Sun Workstation, because it appeared at the peak of RISC's ascendency (April 12, 1989), just 2 days after the Intel i486 was launched, proving that CISC CPUs could achieve RISC levels of performance. The first Intel 486 computer didn't actually appear until September. I'm a fan of RISC. I loved PowerPC and I'm super-glad Apple have switched to ARM-based Macs. But the 1990s were an awkward reckoning for the methodology as vendors strove to stay ahead of Intel despite having far fewer engineers, only to find Intel copying their techniques and often better than comparable RISC computers.
So, skipping back to 1989. The SparcStation 1 was Sun's attempt to compete with PCs by designing a highly-integrated, low-end Sparc workstation. It ran at a blazing 20MHz, delivering about 13 Dhrystone MIPS (and a SpecInt89 of about 13-14 too). This was over twice as fast as the fastest Intel i386DX at the time and about 30% faster than the just announced Intel i486. So, it was impressive. It had 64kB of external cache (no internal cache) and used the bizarre Sun MMU ported from their earlier 68020-based workstations. This MMU doesn't use a Translate Look-aside Buffer, but dedicated SRAM chips to maintain a large, 2-level cache of page translations.
Finally, it has a Sparc V7 CPU, the epitome of a classic RISC design. For example, it has no multiply or divide instructions (just a multiply step instruction: 32 cycles for a 32x32=>64 bit result, but other multiply sizes can be done quicker).
Setting Up Data Transfer
The basic principle is that the disk image (.hd) is divided 8 partitions in SunOS and only 5 of them are used, so assigning some space to a spare partition and then accessing it using dd from either side is relatively easy.
There are several stages to making it work though! I'm using a 320MB HD image (a Sun type 5 drive). This would have been very big for 1989. Standard drives from Sun were 80MB or 104MB. You can install the OS from a CD image as described in the earlier link. It's a horrible textual, menu-driven thing which is easy to get wrong. The critical thing though is that you can install the OS and then later modify the partitions. By convention, disk3 is used for the main HD; partition a is root '/'; partition b is swap (not mounted as such); c is a non-mounted partition that covers the whole drive; g is /usr and h is /home.
For this experiment I didn't quite do an 'easy' setup. Initially one needs to >b cdrom at the bootloader prompt. Then when it says:
| Partition (type letter<cr>) |
Cylinder (prompted) (672 x 512b blocks/ cylinder) |
Blocks (prompted) |
|---|---|---|
| a | 0 | 16800 |
| b | 25 | 102144 |
| c | 0 | 623616 |
| g | 177 | 201600 |
| h | 477 | 303072 |
You should check they all add up and no partitions overlap (apart from partition c which covers the whole disk). Then You need to type label<cr> y<cr> quit<cr> then I typed label<cr> y<cr> quit<cr> just to make sure. Back at the # prompt, type reboot cdrom<cr> and on this run through, type 1<cr> then it'll install miniroot, then type 2<cr> because you've already 'formatted' the disk, 1<cr> to reboot, note the vmunix is now a bit bigger at 802kB instead of about 737kB. If the SS1 doesn't automatically reboot, type >b disk3 at the prompt and it should boot. At the # prompt type suninstall<cr> and you'll be into the installer proper ("Welcome to SunInstall"). Type 1<cr> then n<cr>. Although this means the partitions will be overwritten, the sizes of partitions a, b, c, g and h will be preserved. I then chose the Programmer option by following the on-screen instructions, then finally y<cr> to start. Note also, the installer runs newfs for each of these partitions, which means it isn't changing the partition sizes.
After the basic install, it will complete the installation by asking you to provide extra information. I pressed 2<cr> <RETURN> I set the hostname to SS1mini , chose GMT for the time zone. 2<cr> then 22/12/2025<cr> for the date (UK format) and 11:34:30<cr> for the time. 1<cr> to accept that. 2<cr> (not on a network), y<cr> to accept. Finally I chose a password; I set up a user account with a full name of Julian Skidmore; user name as js; 100 as the user ID (because 0..99 are supposedly reserved) and the same password as root. It then finally completed the installation and dropped me into a login prompt.
I logged in as root ; then typed reboot cdrom to reboot into the cd and typed 2<cr> to use the single user shell; ran format again.
The trick is to steal space from another partition and because a, b, g and h are all mounted as proper filesystems, the obvious place is to steal from the swap partition. We have about 49MB allocated to that, for a 16MB SS1, so stealing around 1.44MB will be OK. Type 0<cr> then partition<cr> then make these changes:
| Partition (type letter<cr>) |
Cylinder (prompted) (672 x 512b blocks/ cylinder) |
Blocks (prompted) |
|---|---|---|
| b | 25 | 98784 |
| d | 172 | 3360 |
Then you need to check all the partitions add up; write the label (label<cr> y<cr>), then quit<cr> label<cr> quit<cr>. Finally you can reboot back into the emulator: reboot disk3<cr>.
You only have to do this once and you're now ready to do data transfer!
Performing A Data Transfer
As a test, I modified a version of dhrystone to provide more accurate results when using time() instead of the µsecond accurate system functions, then tar'd them up into a 40kB tar file. You could use any file as a demonstration. You need to measure the length of the files you want to transfer in this technique of course.
From the SS1 emulator I could then copy dhry.tar to d using:
dd if=dhry.tar of=/dev/sd3d bs=1024 count=40
Then I needed to logout, login as root; then /etc/halt the SS1 emulator and quit MAME. Now I could copy from the hard disk image to the host on my Mac mini using:
dd if=SunHd320.hd of=dhry.tar bs=1024 oseek=57792 count=40
(Since partition d was at cylinder 172 according to format: Partition: Print). If you had created a compressed, chd hard disk, you would need the MAME tool chdman and calculate absolute byte offsets and lengths ( e.g. ./chdman extracthd -i sunos412.chd -isb 84951040 -ib 40960 -o dhry.tar ).
I could then copy back to the SunHd320.hd, but this is a bit non-trivial, because I found dd truncates the file. I needed to do:
cp SunHd320.hd SunHd320B.hd
dd of=SunHd320.hd if=dhry.tar bs=1024 oseek=56112 count=40
Then add the rest of the hard disk image using:
dd of=SunHd320.hd if=SunHd320B.hd bs=1024 iseek=56152 oseek=56152
Finally I could boot back into the SS1 emulator and copy the data back (when logged in as root) using:
dd of=dhry.tar if=/dev/sd3d bs=1024 count=40
I could then untar it using tar -xvf dhry.tar.
Conclusion
MAME provides a real-time emulation of a SparcStation 1 on hardware at least a few hundred times faster (in my case, the 2.5GHz Dual-Core i5 on my Mac mini 2012). To make any emulator truly useful you have to get data in and out of it. However, this emulator is only barely working.
After quite a few dead ends, I realised I could use dd on the SparcStation emulator and the hard disk image on the host side to transfer data in a fairly clumsy way. It's very crude. Still, I have bi-directional data transfer and I can start playing around with some other SparcStation software installs.
