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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?"
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Don't Nurse Old Hardware - Emulate It

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  • Not a bad idea (Score:5, Interesting)

    by mirko ( 198274 ) on Wednesday August 04, 2004 @11:11AM (#9879145) Journal
    I was even considering emulating existing hardware on beowulf clusters, I know it sounds like a troll or deja-vu joke but I mean it : if I have 1000 machines emulated on a beowulf of 1000 machines, then it'll be harder to get downtime if one machine physically crash.
    • Re:Not a bad idea (Score:5, Interesting)

      by rf0 ( 159958 ) <> on Wednesday August 04, 2004 @11:19AM (#9879223) Homepage
      Or for testing you can run a Cluster on a single CPU...

    • Re:Not a bad idea (Score:3, Interesting)

      by photon317 ( 208409 )

      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)

        by zeugma-amp ( 139862 ) on Wednesday August 04, 2004 @01:24PM (#9880603) Homepage

        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.

  • by Jonny_eh ( 765306 ) on Wednesday August 04, 2004 @11:12AM (#9879149)
    Everyone has been so busy emulating the GBA and Xbox that no one has thought about emulating these old servers?
    • by PhilHibbs ( 4537 ) <> on Wednesday August 04, 2004 @11:19AM (#9879233) Homepage Journal
      It's not like there is some pool of emulator writers, constantly considering what the world needs in terms of emulators. The people that write GBA emulators are people that want a GBA emulator. Asking them nicely to write a Pr1me emulator is likely to get you nowhere. You need to talk to the people that want a Pr1me emulator.
    • Christ. The truth is, Slashdot is basically a Gamer site. It's quite abnormal to see a real computer story here.
    • by MoneyT ( 548795 ) on Wednesday August 04, 2004 @11:51AM (#9879601) Journal
      Actualy people have thought about it. The problem is, emulators are all well and good, until you actualy need to access a periphrial.
      • by pla ( 258480 ) on Wednesday August 04, 2004 @01:47PM (#9880885) Journal
        The problem is, emulators are all well and good, until you actualy need to access a periphrial.

        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).
    • There have been PDP and VAX emulation boards available for some time. I believe some of the other big iron is also emulated already. This isn't something new, just new to /.
    • I'm sure its being done as we speak. In 1998, I helped implement a Honeywell 316 emulator to replace a real H316 computer in two F15/F16 diagnostics test stations. The test executive and user programs were all written in H316 assembly language. Seeing that the H316 is no longer in production, the only choice was to emulate the machine given that porting the existing code would have taken an inordinately long time and porting code we don't know about is obviously impossible. The test stations themselves
  • A guess (Score:3, Interesting)

    by NETHED ( 258016 ) on Wednesday August 04, 2004 @11:12AM (#9879152) Homepage
    I will have to guess, 7. Just because its a great number.

    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)

      by doublem ( 118724 ) on Wednesday August 04, 2004 @11:17AM (#9879205) Homepage Journal

      It's called Wintux []
      • This [] is just so very, very wrong.

        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.
    • Umm if you haven't noticed they bought someone else's product.. its not THEIR initiative..

      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 )
  • SimH (Score:5, Interesting)

    by Anonymous Coward on Wednesday August 04, 2004 @11:12AM (#9879154)
    Bob's emulation software SimH is a *fantastic* bit of kit. Runs vanilla OpenVMS without modification - VMS doesn't even know it's in a sim until you tell it so when you licence it.
  • or how many (Score:5, Funny)

    by Anonymous Coward on Wednesday August 04, 2004 @11:12AM (#9879155)
    pentium IV's can you emulate on a PowerPC?
    • Ehh about .75
    • Re:or how many (Score:3, Interesting)

      by bhtooefr ( 649901 )
      Quite a lot, and viably too. However, the REAL question is: how many Pentium 4's does it take to emulate a PowerPC at a usable speed, with and without Altivec (G4 and G3 emulation)? PearPC appears to get about a 75MHz G3 equivalent speed on an A64 3200+. NOT good at all.
  • I disagree (Score:5, Funny)

    by Rosco P. Coltrane ( 209368 ) on Wednesday August 04, 2004 @11:12AM (#9879159)
    emulating old servers may be a better way to keep them running that servicing the physical machines.

    I disagree. It's not the same thing.

    -- Signed: your friendly PDP-11 system operator downstairs, 3 years from retirement.
    • by Anonymous Coward on Wednesday August 04, 2004 @01:16PM (#9880542)
      Totally agreed --

      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.

  • This is all well and good assuming there is an emulator for your mainframe. But what about lesser known mainframes such as the Prime. Where at their hay-day there were one of the big players but then they quickly moved to obscurity. There are a lot of other mainframes other then VAX and IBMs suff. And a lot of them are slightly obscure and near impossible to find emulators for.
    • DEC never made mainframes - there was one "Mainframe-class" VAX, the 10000, but DEC always conceded that the VAXen were minicomputers.

      Don't get me wrong - i'm not beating on them. I have three of my own...
      • The PDP-10 [], which preceded the VAX (and had a 36-bit word size) is considered by many to have been a mainframe.
      • DEC never made mainframes
        The DEC 36-bit systems [] were generally considered to be in competition with IBM's mainframes. DEC management did try to keep their perceived capaability just below the mainframe range to avoid provoking too strong a counter-attack from IBM - a strategy which many think was the beginning of the end for DEC.


    • You mean Pr1me?
      • Well kinda the company had 2 names Pr1me in like 1983 then later it became Prime. I am currently sitting behind about a hundred books that says "Prime" on it. I probably have enough resources available to make my own emulator if Only I had the time.
    • But what about lesser known mainframes such as the Prime.

      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
  • by gschwim ( 413230 ) on Wednesday August 04, 2004 @11:13AM (#9879171)
    ...on how many bugs your emulating under your Windows 2004 Emulator Edition.
  • by z0ink ( 572154 ) on Wednesday August 04, 2004 @11:14AM (#9879177)
    .. but you forget the reason people dont upgrade is that it costs money to do so.
  • by AdeBaumann ( 126557 ) on Wednesday August 04, 2004 @11:14AM (#9879178) Homepage
    Before I even R'd TFA, I thought about one big problem:

    How are you going to emulate a 5.25 inch drive to read old disks?
  • by Anonymous Coward on Wednesday August 04, 2004 @11:14AM (#9879181)
    Although this is a very good idea I question the stability of a new emulator vs an old proven system.

    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?
    • by GeoGreg ( 631708 ) on Wednesday August 04, 2004 @12:25PM (#9880004)
      Well, for one thing, the old, (formerly) stable hardware may be failing. It might be easier to get hold of a PDP/11 emulator being used (and, hopefully, improved) by multiple organizations than to attempt to translate the in-house PDP/11 assembly code into something that will run on a PIV Linux box. Especially if the people who wrote the legacy app are retired/laid off/dead.
    • by quarkscat ( 697644 ) on Wednesday August 04, 2004 @12:28PM (#9880032)
      There is no equivalence. For instance, DEC VMS
      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
  • If the DEC VAX systems are so antiquated, wouldn't it make more sense for businesses using these systems to simply upgrade to newer/better technology? I mean even if they have incredibly stability and "wow" factor, wouldn't it be easier than both solutions just to upgrade the software to newer systems. Uptime on many linux/unix systems are just fine for most usage, and QNX has their real time fail proof operating system, but I doubt people using VAX would even need something that powerful.
    • If it works, don't fix it.
    • by CarrionBird ( 589738 ) on Wednesday August 04, 2004 @11:19AM (#9879234) Journal
      just upgrade the software?

      Methinks you underestimate how badly software projects of that sort often go.

    • but I doubt people using VAX would even need something that powerful.

      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!

    • If the DEC VAX systems are so antiquated, wouldn't it make more sense for businesses using these systems to simply upgrade to newer/better technology? I mean even if they have incredibly stability and "wow" factor, wouldn't it be easier than both solutions just to upgrade the software to newer systems.

      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)

    by 5m477m4n ( 787430 ) on Wednesday August 04, 2004 @11:16AM (#9879196) Homepage
    by Bob Supnik, Sun Microsystems

    Gee, I wonder why he would be recommending buying new servers?
  • Is there a simulator for the TX-1? People talk about how great Sutherland's Sketchpad software was, and it ran on the TX-1. Is there even enough public information to simulate it, and does the Sketchpad code still exist?
  • Awesome, imagine how many PDP-11 one can emulate to operate a therac-25. How many people one could kill!

    amazing ;)
  • by maynard ( 3337 ) <> on Wednesday August 04, 2004 @11:18AM (#9879216) Journal
    I know of a PDP-11/73 which to this day is still cutting sheet metal for a duct factory. The damn thing just won't die. And they're not likely to emulate since the I/O board interface between the computer and their machine tools would be more expensive to implement on a custom PCI card, along with emulation drivers, than simply buying excess used PDP-11 parts. Someday they'll have to face the music and actually buy a commercial solution, but for the moment they continue maximizing their return on investment for a computer system originally purchased well over thirty years ago. And why the hell not? --M
    • by Anonymous Coward

      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
  • So how many PDP-11's can you run on a Pentium 4 anyhow?"

    in finding This article [] and this article [] 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)

      by -brazil- ( 111867 )
      Such a "translation" would be beyond meaningless. The architecture is fundamentally different, and most of the P4's cycles would have to be spent on emulating/accounting for quirky little hardware details or features. That's why it takes a 100 MHz Pentium (if not more) to properly emulate a 1 MHZ C64
  • SimH (Score:2, Redundant)

    by awx ( 169546 )
    Bob's emulation software SimH is a *fantastic* bit of kit. Runs vanilla OpenVMS without modification - VMS doesn't even know it's in a sim until you tell it so when you licence it.

    (re-posting my anon comment)
  • by ErroneousBee ( 611028 ) <neil:neil h a n c o c k . c o .uk> on Wednesday August 04, 2004 @11:19AM (#9879229) Homepage
    There are emulators for old IBM mainframes (S360 S370). Hercules is one of these.

    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.
  • I once considered writing an emulator for the HP1000 - until I realized it is totally impossible to find documentation on the hardware. I guess that is a major problem for most of these old systems.
  • Let's find out! (Score:2, Informative)

    So how many PDP-11's can you run on a Pentium 4 anyhow?

    You could shell out some bucks for Ersatz11 [] and find out. It runs under Linux, and it runs fast. You can even attach Q-Bus and Unibus hardware with an adapter.

    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.
    • by Rorschach1 ( 174480 ) on Wednesday August 04, 2004 @11:37AM (#9879446) Homepage
      Funny? That should be modded 'informative.' I've never been hospitalized, but I did wind up with a wrist brace for a week or two thanks to some RA-92 hard drives.

      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.
  • by garver ( 30881 ) on Wednesday August 04, 2004 @11:25AM (#9879301)

    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)

    by Gropo ( 445879 ) <> on Wednesday August 04, 2004 @11:26AM (#9879311) Homepage Journal
    SIMH [] Website.

    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 main problem with this is that a lot of the emulator software doesn't get upgraded. Where I work, we have a 5250 terminal emulator with a specific macro language that will only run on Windows 95/98/NT 4.0. We are already emulating a terminal. Who wants to emulate a 5250 terminal on an emulated windows 95 machine?
  • Problem is... The WOW factor on these servers has gone from WOW look what it can do. To WOW your still using that.
  • So many pitfalls! (Score:5, Interesting)

    by ikegami ( 793066 ) on Wednesday August 04, 2004 @11:29AM (#9879347)
    The article does well by pointing out a great list of problems that can be encountered when emulating a machine.

    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--) { /* nothing */ }
    Imaginine executing that on an emulator that didn't pay any attention to timing?
  • ...if you actually need the physical computer bits.

    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 []
  • Bob Supnik! (Score:4, Interesting)

    by ackthpt ( 218170 ) * on Wednesday August 04, 2004 @11:32AM (#9879375) Homepage Journal
    Man, I haven't seen that name in 20 years!

    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.

  • by Anonymous Coward on Wednesday August 04, 2004 @11:32AM (#9879377)

    So how many PDP-11's can you run on a Pentium 4 anyhow?

    All of them? ;-)
    • Re:Just a guess ... (Score:4, Interesting)

      by earthforce_1 ( 454968 ) <earthforce_1@[ ] ['yah' in gap]> on Wednesday August 04, 2004 @12:32PM (#9880080) Journal
      Actually, it would be fun to see how many pentium-4's you could fit inside a PDP-11 case.

      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!
  • There's nothing to stop HP from making replacement parts on an ongoing basis if they wanted to. As long as there is a market for the repair services, why landfill working hardware?
  • Usermode Linux (Score:3, Interesting)

    by Brian Blessed ( 258910 ) on Wednesday August 04, 2004 @11:40AM (#9879484)
    I've recently done this with a small webserver to keep it running. Some sort of deposit had appeared on top of the electrolytic capacitors on the motherboard, and the machine became unbearably unstable.

    I took out one of it's mirrored drives and connected it in a different (larger) machine and then booted it using Usermode Linux [].
    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.
  • by Phil Wherry ( 122138 ) on Wednesday August 04, 2004 @11:42AM (#9879504) Homepage
    For those interested in trying VMS on Linux using the SIMH emulator (entertaining if you once used it), I've written a set of installation instructions [] that might be of some use.

  • Emulation (Score:4, Interesting)

    by PingPongBoy ( 303994 ) on Wednesday August 04, 2004 @11:42AM (#9879510)
    I've written emulators for devices. It depends on what you want to achieve. Emulating the interface may be relatively easy. If you used an old server to provide specific data or perhaps some kind of interface to another service, well you don't need to duplicate the entire server, you just have to implement a "jumper" system to provide a different path for the information flow.

    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.
  • by caveat ( 26803 ) on Wednesday August 04, 2004 @11:46AM (#9879553)
    the PDP-8/e Simulator for Macintosh [] is a LOADED system (up to 32K words of memory, KE8-E Extended Arithmetic Element, ASR 33 Console Teletype, ASR 33 Auxiliary Teletype, PC8-E High Speed Paper Tape Reader and Punch, RK8-E Disk Cartridge System, LP8-E Line Printer, and a KC8-EA Programmer's Console) that runs a quite a bit faster [] than the original - fastest benchmark is a G4/450 at about 22x; my 2x1.25 runs the tests well under 1sec. If you need to support an -8 legacy, this seems like the logical way to go.
    • Check out [] which provides a one-stop resource for emulation on Mac OS and Mac OS X. They list 35 different computer systems for which you can get emulators. Most of them appear to be free.

      Acorn Atom, Acorn BBC Micro, Amstrad CPC, Amstrad PCW, Apple I, Apple II, Apple ///, Atari 800, Atari ST, Baby (SSEM), Commodore Amiga, Commodore 64, Commodore VIC-20, CP/M, Edsac, IBM Series/1, Macintosh 68000, Memotech MTX512, MIPS R2000, MO5, MSX, Oric, PC-9801, PDP-8/E, SAM Coupé, Sinclair Q
  • by mykepredko ( 40154 ) on Wednesday August 04, 2004 @11:49AM (#9879581) Homepage
    About fifteen years ago, I was involved in the retirement of a number of older computing systems (specifically IBM "Series/1", "System/7" and "1130"s) used in manufacturing. At the time, these systems were critical in supporting older products (most notably FAA radar displays) but had been withdrawn from regular IBM support and parts were only available from returned equipment.

    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.

    • Wow, another old hand who's done GPIB!! That's actually how I got my start as a professional programmer - we were running a bunch of gear that used the GPIB bus, either off of some HP controller (which ran HP Basic) or some old Tectronics terminals

      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
  • by poot_rootbeer ( 188613 ) on Wednesday August 04, 2004 @01:15PM (#9880528)
    But would a software-based emulator accurately reproduce the behavior of the infamous "More Magic" switch? []

    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?

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