Don't Nurse Old Hardware - Emulate It 403
gManZboy writes "Bob Supnik, former team lead for DEC's VAX microprossesor, has an article up on Queue about his Computer History Simulation Project and how emulating old servers may be a better way to keep them running that servicing the physical machines. So how many PDP-11's can you run on a Pentium 4 anyhow?"
Not a bad idea (Score:5, Interesting)
Re:Not a bad idea (Score:5, Interesting)
http://openssi.org/ssiuml-howto
Rus
Re:Not a bad idea (Score:2)
Re:Not a bad idea (Score:3, Interesting)
Yeah they have that already for x86 on x86, VMWare's high-end enterprise product allows you to run VMWare on several machines and transparently move system images between physical hosts without taking any (perceivable) downtime. So hardware maintenance can be done without interrupting your "servers". Of course if the hardware crashes, any system images running on that particular hardware go down hard, but they can fail over to another peice of hardware and come up and fsck (or the equivalent in your OS of
Re:Not a bad idea (Score:5, Interesting)
allows you to run VMWare on several machines and transparently move system images between physical hosts without taking any (perceivable) downtime.
I've seen this in action, and it is very impressive. Imagine, if you will a MS-SQL (ugh) database running in a VMWare session. Let's say you need to perform some hardware maintenance on the system it is running one. Using their control console, you can "migrate" the entire emulated session while it is still taking transactions to another system with a barely perceptable pause (a second or so) between when one server stops executing and the next server starts.
Disclaimer: I don't have anything to do with VMWare other than the fact that I use it.
Comment removed (Score:5, Informative)
Can't believe no one's thought of this (Score:3, Insightful)
Re:Can't believe no one's thought of this (Score:5, Insightful)
Re:Can't believe no one's thought of this (Score:2, Troll)
Not very fair... (Score:4, Funny)
"The truth is, Slashdot is basically a Gamer site."
Oh come on now, that's not fair. We also talk about pr0n.
Re:Can't believe no one's thought of this (Score:4, Insightful)
Re:Can't believe no one's thought of this (Score:4, Insightful)
So you emulate those, as well... And usually, they take a lot less to emulate than the core system.
As a trivial example, consider the peripherals available even on previous-gen consoles... You have 3rd party joysticks, mice, keyboards, cameras, tape drives, printers(?), etc. All those eventually end up emulated, if enough people needed them.
The same goes for something like a PDP-11 or VAX 11/750 or the like. You have some odd storage devices (that store a tiny fraction of modern HDDs, thus you can emulate them with an image file). You have printers (emulatable with... printers!). Perhaps really ancient input devices such as a cardreader (scanner -> conversion tool -> file). No doubt other exotic peripherals exist, but you can somehow emulate them all.
The conceptual problem with dealing with peripherals I think lies in just how much we've advanced since the days of Big Iron... Even for emulating CPU-cycle-critical hardware interactions, you can deal with it in emulation, by pure brute-force. Consider the 11/780, which ran at a whopping 6MHz. On a modern P4, that means you have over 500 CPU cycles per emulated cycle (and while the P4 can push through more than two ops per clock, the VAX only managed one instruction per 6(?) clocks, meaning you realistically have over six thousand real instructions per emulated one, on average). With six thousand instructions to burn, you could emulate your VAX while still getting a good framerate playing Super Metroid on an emulated SuperNes in the foreground.
That I know of, only the humble old laserdisc has thus far resisted attempts at perfect emulation, due to using an analog encoding scheme (rather than storing bits, it actually encoded the raw NTSC or PAL signal handled by the TV. And depending on what sort of access to them you need, even that problem has a way around it, via an MPEG rip and a frame file (ala Daphne).
Re:Can't believe no one's thought of this (Score:3, Insightful)
Fair enough point - But in that case, I would have to consider the computer secondary to the machine itself - I don't know your specific situation, but the computer most likely did data collection and analysis. The controller-proper I would consider part of the "peripheral", and search for the easiest-to-tap connection as the point to break away from reality and into emulation.
I'll admit, I hadn't considered that point. You can't emulate a fatigue te
Re:Can't believe no one's thought of this (Score:3, Insightful)
Re:Can't believe no one's thought of this (Score:3, Interesting)
A guess (Score:3, Interesting)
But seriously. Emulators are the way to go. I know that w/ Microsofts new initiative to let linux apps run in Windows, emulators are going mainstream. Yes, for all you anti-MS people, Windows is mainstream.
I was looking for the article about Windows Linux thing, but I cannot seem to find it at the moment.
Re:A guess (Score:4, Funny)
It's called Wintux [matthewmiller.net]
Oh my god (Score:2)
Don't get me wrong, a program that lets linux programs run in windows isn't a bad idea, but that picture... it just should not be.
When napster went legit, I had images of the napter cat, once a symbol of freedom, as a borgified drone of the RIAA, that picture sends the exact same shivers down my spine.
Microsoft's initiative? My foot…. (Score:2)
And have you heard of VMWare? its been a viable product for some time now.. ( this is perhape the reason they bought conectix in the first place )
( other, even older, free sandbox applications not withstanding )
efficient versus speed (Score:3, Insightful)
SimH (Score:5, Interesting)
Re:SimH (Score:5, Interesting)
or how many (Score:5, Funny)
Re:or how many (Score:2, Funny)
Re:or how many (Score:3, Interesting)
I disagree (Score:5, Funny)
I disagree. It's not the same thing.
-- Signed: your friendly PDP-11 system operator downstairs, 3 years from retirement.
Re:I disagree (Score:5, Funny)
How can you emulate the experience of getting a maintenance notice
in the mail from DEC that included a software patch on DECtape and
explicit instructions on how to patch the hardware via wire-wrap?
Or getting out the oscilloscope to set the baudrate on your PDP-11/05? And then
booting said 11/05 by
1) entering a program in octal via the front panel that is just
good enough to read a bootstrapper from paper tape,
2) jumping to the boostrapper from the front panel thus
3) reading a second boostrapper from paper tape
which in turn has a boostrapper to read from disk,
4) which in turn finally gets around to reading the bootblock
5) which might actually know something about booting RTS from that RK05 or RL10 or what-have-you.
All Well and good. (Score:2)
Re:All Well and good. (Score:2)
Don't get me wrong - i'm not beating on them. I have three of my own...
Re:All Well and good. (Score:2)
Re:All Well and good. (Score:2)
sPh
Re:All Well and good. (Score:2)
Re:All Well and good. (Score:2)
Re:All Well and good. (Score:3, Funny)
How sad for me to find out that not only am I obsolete, I'm also obscure. I remember PrimeOS fondly if for no other reason than it was where I cut my teeth as a young hacker.
Would have been about 1984, dialing in to a univeristy's Prime in another state. Me on my Commodore 64 with my Microbits 300 baud modem (I was the fastest kid on the block. Everyone else had 110 or baudots). It was like NetHack, but in real life. Learned to get in. Lea
Re:All Well and good. (Score:5, Funny)
Re:All Well and good. (Score:3, Interesting)
It depends... (Score:3, Funny)
Emulation is great .. (Score:5, Insightful)
Re:Emulation is great .. (Score:5, Insightful)
Good idea... but... (Score:5, Insightful)
How are you going to emulate a 5.25 inch drive to read old disks?
More important question: (Score:3, Insightful)
Re:More important question: (Score:5, Funny)
Re:More important question: (Score:3, Funny)
Re:More important question: (Score:2)
Re:Good idea... but... (Score:2, Insightful)
Re:Good idea... but... (Score:4, Informative)
Re:Good idea... but... (Score:4, Funny)
Damm are you young, when someone says 5.25 disks I dont even think too old.
Bring on the 8 Inchers, now those were the days they also fly great, late Friday afternoon we would all let loose by flying them around like frisbees, all fun and games till someone get a corner in the eye.
Re:Good idea... but... (Score:4, Funny)
late Friday afternoon we would all let loose by flying them around like frisbees
And then I saw your user id...
Re:Good idea... but... (Score:2, Informative)
Emulating a 5.25" isn't actually 100% necessary. The FDC that controls a 3.5" floppy is quite capable of controlling a 5.25" floppy in all three modes (DSDD, SSDD and SSSD) for reading any 'PC compatible' formatted disk. There are also a number of hardware options, such as the CatWeasel, that cen be used to drive a standard 5.25" drive to read non-PC Compatible disks.
Admittedly, you're still probably better off just using such a drive to create images of real world disks. Emulating drives with images is s
Re:Good idea... but... (Score:4, Interesting)
You use your old VAX to make disk images for you before you give it to a collector.
Re:Good idea... but... (Score:3, Informative)
Write really good software! Even the Apple II Disk II drives, which depended heavily on the CPU have been emulated at the hardware level. Rather than reading sectors from a file, some image formats contain the stream of bytes read by the drive hardware. [Data encodings, bytes per sector and address and data marks were defined in *software* rather than by a disk controller chip. There were a large number of screwball formats, particularly in
Re:Good idea... but... (Score:5, Interesting)
At 9600bps you can transfer even the highest density 8" floppy in under half an hour!
(Ah, shades of my college job where our 'network' was oddball generic-MSDOS machines all with serial links to the VAX 11/750 in the back room with *Three* 30MB 14" Winchester drives, almost 100MB online, rah! Don't try and power all three up at once, though, or you'd blow the 100Amp breaker.)
The Stability of New Products vs Old (Score:5, Insightful)
By using the original the kinks have already been worked out, quirks are known and understood, and everything just works.
By creating an emulator you have bugs to smash, that's just the way software is. Also keep in mind this seems to apply to big businesses (financial, medical) and large organizations (NASA) with legacy hardware. Since the stability of these systems is absolutely crucial why would they want to switch to a new, unproven, buggy system that stick with the old?
Re:The Stability of New Products vs Old (Score:5, Insightful)
Re:The Stability of New Products vs Old (Score:4, Insightful)
was used as the design "core" for Microsoft's
Windows NT. I have known of DEC VAX hardware
that ran continuously for 5 years without a
warm reboot, let alone a system shutdown. The
Microsoft OS often needed to be rebooted daily.
The hardware that Microsoft runs on is not as
reliable as the old DEC VAXs, as a rule. The
short term emulation of a legacy system is not
the same as replacing it. For exammple, an IBM
z/390 running MVS might be able to run 1000
linux servers, but in terms of reliability
(the proverbial 5 Nines), that z/390 could not
be replaced with 1000 linux boxes, or even 2000.
The old adage "They just don't make things the
way they used to." applies here. New hardware
costs are way down, as are HW/SW maintenence
costs, but the reliability of the new gear is
underwhelming.
DEC VAX -- why not port?! (Score:2, Insightful)
Re:DEC VAX -- why not port?! (Score:2)
Re:DEC VAX -- why not port?! (Score:5, Insightful)
Methinks you underestimate how badly software projects of that sort often go.
Re:DEC VAX -- why not port?! (Score:2)
VAX users aren't typical, they're likely hospitals, banks or gonvernment institiutions that rely on the incredible stability. Besides, VMS is alive and kicking, why redo software more than necessary? Besides, Darl hasn't sued VAX owners yet!
Why not port? Why bother? (Score:3, Insightful)
Say you've got an existing system performing a particular task - maybe your inventory or payroll system, and it's coping with the load and has sufficient flexibility to allow you to make changes in respo
I wonder why... (Score:5, Insightful)
Gee, I wonder why he would be recommending buying new servers?
Re:I wonder why... (Score:3, Insightful)
And while I hope it never happens to you, if you happen to get into hospital, there is quite some chance that your information will be registered on a.... VAX. that is right, an old, according to you obviously unusable VAX.
Next time you transfer some money, chances are quite good that your order will be processed by... again one of those unusable vaxen...
I suggest you delve a bit into the matter before laugh
TX-1 (Score:2)
Emulate death! (Score:2)
amazing
PDP-11s *still* in use! (Score:5, Interesting)
Re:PDP-11s *still* in use! (Score:2, Interesting)
Nearly all modern thermonuclear delivery systems are tested at some point on DIDACS. The system is based on a PDP-11/34, except for the TVC controller which is a PDP-11/24.
Been running for thousands of tests without a hitch. I know, because I wrote the code about 15 years ago and periodically I still meet the techs who are still running it.
I sincerely doubt you could emulate a unibus machine running RSX or TSX (we're talking REALTIME operating systems here boyz) on any PC-type architecture. We had t
Re:PDP-11s *still* in use! (Score:4, Interesting)
Re:PDP-11s *still* in use! (Score:3, Informative)
At the mill I worked at our oldest major piece of equipment is about 80 or 90 years old. No real reason to upgrade it, it does it's job. The area of the mill that I worked at, the machines were about 40 years old, controlled by a 10 year old VAX who communicated with even older PLCs to do the real-time work, and yet the steel we produce is among the highest qualit
In answer to (Score:2)
in finding This article [wikipedia.org] and this article [ed-thelen.org] which go in to good detail about PDP-11 specs, I can't figure out how to translate them into Pentium 4 equivalent speed, anyone care to help me? Would be interesting to find out anyways.
Re:In answer to (Score:2, Informative)
SimH (Score:2, Redundant)
(re-posting my anon comment)
Software License barriers (Score:5, Interesting)
Unfortunatly, the massive cost of liscencing the MVS (OS/390, zOS) operating systems means there is no way that a normal user can run a PC based mainframe. IBM employees can do it, of course.
I guess thats also true for the PDP-11 and many old Vaxen, its just cheaper to migrate to new hardware/OS.
HP1000 (Score:2)
Let's find out! (Score:2, Informative)
You could shell out some bucks for Ersatz11 [dbit.com] and find out. It runs under Linux, and it runs fast. You can even attach Q-Bus and Unibus hardware with an adapter.
You might be a vax geek if... (Score:5, Funny)
Key traits identifying individuals tendencies towards abnormal preoccupation with VAX computer systems
9. When talking about building software you make reference to
compilation times in weeks and days instead of minutes and seconds.
8. You stopped purchasing new furniture when you realized that
your computers work just as well.
7. Your electricity bill is more than your monthly rent payment.
6. You've been hospitalized with muscle strain injuries after
performing some routine hardware maintenance on your computer.
5. You don't have an SO, but it's okay because your computer keeps
you warm at night.
4. While doing laundry, you occassionaly have a mental lapse and try to
wash your socks and underwear in your 11/750.
3. Friends who visit you want to know why there are old-time movie reels
stuck on your refridgerator(s).
2. Your house is pleasantly warm in the dead of winter, even with the air
conditioning turned all the way up.
1. The lights in your home dim or flicker when you reboot.
0. It doesn't matter to you if someone else's computer is faster because
you know your system could smash theirs flat if it fell over on it.
Re:You might be a vax geek if... (Score:5, Informative)
Seriously, if anyone wants a free VAX 6000-510, let me know. I need the garage space back. I'm on the central coast of California. I'll even throw in a MicroVAX II or two if you want. They make good end tables.
Nice idea, but good luck (Score:3, Funny)
Regression testing. Emulation's nice, but it ain't the same as the original hardware. Which means, people will need to regression test. Trick is, the people that know what that old PDP-ll is actually doing retired a long time ago. So who's going to write the test cases?
SIMH URL (Score:3, Funny)
Been wanting to buy an old 11/780 shell for a while. Not for a bar, but to mount both my Mac and Gaming PC innards in. This'd be a real trip to run as an emulator during parties. Now to interface the VT-120... Hack the shell I suppose. Run everything USB. >:D
The problem with this... (Score:2)
Changing WOW factor. (Score:2, Funny)
So many pitfalls! (Score:5, Interesting)
Some of the projects on which I work are for nuclear power plants, many of which here in Canada use computers from 1972 -- I was born in 1976 -- to control the plant. While spare parts are dwindling, the prospect of having to retest all of the code is daunting, not to mention the costs of making a program as complex as an emulator in the first place.
I've seen (the assembler equivalent to) the following code used in embeded processors to perform a sleep():
counter = 500; while (counter--) {
Imaginine executing that on an emulator that didn't pay any attention to timing?
Re:So many pitfalls! (Score:4, Informative)
Any half-decent emulator will pay attention to cycle counts. It's one of the few things that distinguishes an emulator from a virtual machine. Take MAME for example - all the CPU emulation in there tracks cycles.
You Can't Emulate Hardware... (Score:2)
Maybe you can run a virtual machine on a Linux box that lets you have a little software VAX on your PC, but try keeping your beers cold in it [glendale.ca.us]
Bob Supnik! (Score:4, Interesting)
I have such warm, fuzzy memories of hacking a PDP 11 and rabidly tearing away the wrapping from each DEC Professional magazine that graced my mailbox...
Yeah, emulation sounds more reasonable than what some nut did, he got the schools old PDP 11/50, with 1 TU16 and 2 RP04 drives and had his house (I sh!t you not) raised 12 inches so he could set it up in the basement. No idea what's happened since.
Just a guess ... (Score:5, Funny)
All of them?
Re:Just a guess ... (Score:4, Interesting)
I miss those 8 inch 100K? floppy drives though - those were the days when floppy lived up to its nam, and the drives made interesting squeaking noises while they were being read. I still have a couple of them downstairs, I was part of the last class that used PDPs before the university retired the old 11/70.
The PDP OS had a weird (and annoying habit) of automatically making numbered backups every time you saved - in theory sounds like a good idea, except with an entire class editing and saving assignments, the main drive ran out of space and the whole system froze every 15 minutes, and we had to hunt down the TA to reboot it. "Delete your files, delete your files" was a cry heard every 5-10 minutes in the lab, lest the whole system hang and die yet again.
Back in the 1970's, that astronomically expensive PDP 11/03 in the Heathkit catalog was my dream machine, as it was the only true 16 bit PC on the market. I even bought the paper tape software and manuals for it!
Why bother (Score:2)
Usermode Linux (Score:3, Interesting)
I took out one of it's mirrored drives and connected it in a different (larger) machine and then booted it using Usermode Linux [sourceforge.net].
I found it was best to be running 2.6.7 on both the host and the uml and it is bridged onto the host's network, so it appears exactly as before.
- Brian.
VMS-on-Linux with SIMH (Score:3, Informative)
Phil
Emulation (Score:4, Interesting)
Emulating an device comprehensively just to simplify servicing it could be futile or infeasible when you need to know the fine details of the device's characteristics. The manufacturer of a device might supply an emulator but I wonder just how many PDP-11's or machines lacking backwards compatibility still provide a vital nonupgradable function.
One may point to certain programs that used to run in DOS or in my case Win95 that don't run in XP. I want to speed up these programs on new hardware without having to buy the latest version. This is the downside of using Windows - if backwards compatibility is broken, a faster processor may force an expensive upgrade. Then again, all this backwards compatibility could be slowing Windows down.
PDP-8/E runs great on OS X (Score:5, Informative)
Mac OS X Emulates 35 Computers (Score:3, Informative)
Acorn Atom, Acorn BBC Micro, Amstrad CPC, Amstrad PCW, Apple I, Apple II, Apple
Simulation/Emulation vs Conversion (Score:5, Interesting)
I could appreciate the article's comments about engineering detective work; we had some source code on paper, some source and binary code archived on disc and some binary code saved on cassette tape (seriously). Product, tester and controller documentation was spotty to say the least. For the most part, we had enough understanding of what was happening to be able to recreate the test specifications for all the products.
The big problem was understanding actual timings and electrical parameters; few of the part numbers were built from standard TTL ("VTL" in IBM parlance) and most were built using IBM "SLT" technology implementing RTL and DTL logic.
After collating all the data we had, we decided we could: we could simulate the controller operations in a PC. In many cases, we could emulate the operation of the controller/tester hardware with basic digital I/O cards connected to a PC. Finally, in quite a few cases we were completely on our own due to unusual (for today) electrical requirements.
Due to the large number of part numbers (1500), we wanted to come up with a single solution that made the most sense and, ideally, worked for all the different part numbers. We looked at simulating the controllers with PCs and passing the I/O to the old tester hardware, emulating the tester using a PC with I/O cards or converting the tests to run on a standard InCircuit Tester (ICT).
In virtually all the cases, it made the most sense to convert the tests to run on a standard ICT tester (GenRad (new Teredyne) 228x was chosen) rather than simulate or emulate the hardware. The conversion applications generally converted the binary code into digital I/O operations (or GPIB instrument I/O) rather than come up with compilers for the original source code (although we did do this in one case). This was still a rather large job, but it was completed before parts sources for the old controlling computers completely dried up.
I suspect that from the lack of hardware interfacing information in the article, the author has run into similar problems. Despite that, having a simulator could be very useful in understanding how an old computer system operated and what is required to properly emulate/convert it into more modern hardware.
myke
Re:Simulation/Emulation vs Conversion (Score:3, Interesting)
We used some CEC corp IEEE-488 (aka GPIB) cards and an emulator to emulate that old HP basic. Then, as the programs were in BASIC, the natural progression was to the Microsoft BasComp compiler, then to the PDS. Then windows and VB came along, and us old hands
Emulators aren't perfect (Score:3, Interesting)
That's a serious question, by the way. How can it be proven that an emulated system will perform exactly the same way that the original system would?
Consider that even among the most popular emulators, those for videogame consoles and handhelds, you won't find many claimed by their authors to have more than 99% compatbility.
Yes, gaming hardware may possibly be more difficult to emulate than well-documented business hardware due to the number of custom chips that effectively have to be reverse-engineered, but do you want to migrate your mission-critical systems from physical hardware to emulated hardware only to find that they depend on the 1% of functionality that's not accurately emulated?
Re:none. (Score:5, Funny)
Not to anyone who's ever tried to pick one up!
My First (Score:2, Funny)
Re:My First (Score:5, Funny)
An LED-screen-based terminal emulator with a 300 baud modem dialing up to the PDP 11 shouldn't really count...
Re:legal issues? (Score:5, Funny)
I think they patented some aspects of emulation, mainly to shut down people selling GBA emus for palmtops.
Given the current state of patent law, chances are that any universal Turing machine now owes Nintendo royalties.
Re:I agree! (Score:4, Insightful)
They end up with still failing "virtual" hardware, and the only consolation is that if they persist long enough, they may eventually fix it completely. Oh, at least until they need to port the emulator to Windows 2009 Gold Pro edition on the Pentium 9, then it bugs out again.
Start porting the damn apps, or rewrite them. And even as you're doing this, plan for the next changeover in 10-15 years.