Re: Someone's confused
> On Jun 8, 2020, at 6:40 PM, Antonio Carlini via cctalk > wrote: > > On 08/06/2020 21:54, Chuck Guzis via cctalk wrote: > >> Although there are exceptions. I recall that it was possible, using >> large page sizes on the CDC STAR-100 to execute an instruction that >> could never get started. The STAR had 512KW (64 bits) of memory and a >> large page size was 64KW. A typical vector instruction could require 6 >> addresses for source, destination and control vectors. Put the starting >> address of any of these in last 8 words of a page and the hardware >> faulted preemptively for next page. It was kind of funny to watch; the >> P-counter for the user never budged, but the pager was sucking up time >> like crazy. I think someone eventually devised a check in the pager for >> this case, but I'm not certain. >> > > There was a standard VAX quiz question which was something along the lines of > "what's the largest number of page faults can a single (valid) instruction > cause" and the answer was surprisingly large (in the region of 50+ although I > can no longer remember the details. I would have thought a lot more than that, for string instructions with long operands. Re the STAR thing, that reminds me of a bug I encountered a decade or so ago on a high end MIPS architecture processor whose manufacturer shall remain nameless. It would prefetch instructions, issuing memory reads to fill the cache if necessary. So far so good. But if you hit a backward branch and then a prefetch for an address past that branch completed, the CPU would consider that access wasted and throw away the data. It wouldn't put it in the cache -- so the next time through the loop you'd get that memory reference again, and again, every iteration. This actually broke things in a cache flush operation because that required the execution of some intensely hairy code that was required to run without any extra cache misses. This bug meant that you'd always get a cache miss at the end of the loop. The fix required some additional very hairy code to hop ahead through address space to get those cache lines actually into the cache... paul
Re: Someone's confused
On 08/06/2020 21:54, Chuck Guzis via cctalk wrote: Although there are exceptions. I recall that it was possible, using large page sizes on the CDC STAR-100 to execute an instruction that could never get started. The STAR had 512KW (64 bits) of memory and a large page size was 64KW. A typical vector instruction could require 6 addresses for source, destination and control vectors. Put the starting address of any of these in last 8 words of a page and the hardware faulted preemptively for next page. It was kind of funny to watch; the P-counter for the user never budged, but the pager was sucking up time like crazy. I think someone eventually devised a check in the pager for this case, but I'm not certain. There was a standard VAX quiz question which was something along the lines of "what's the largest number of page faults can a single (valid) instruction cause" and the answer was surprisingly large (in the region of 50+ although I can no longer remember the details. Antonio -- Antonio Carlini anto...@acarlini.com
Re: Someone's confused
On 08/06/2020 20:49, ben via cctalk wrote: But speed is relative. They changed computers where I was studing electronics from a IBM-1130 to a VAX (something) in 1982. I could use the IBM but the not VAX because they would have too many users if that division had access to the VAX, and the electonics section had PDP8 computers anyway. So I suspect any VAX with one user would be faster than REAL world machines in 1980's. All my VAXes are now single user and quite likely to remain that way :-) Maybe if I ever get a house with a very large basement or very large outbuildings that can act as a computer room, then that might change. But for now, my VAXstation 4000 M9x is faster than almost all of my other VAXes (not counting SIMH). Antonio -- Antonio Carlini anto...@acarlini.com
Re: Restarting Old Amiga's
On 08/06/2020 21:24, Ethan O'Toole via cctalk wrote: On the Amiga A501 trap door memory expansion, there is a battery for the time clock that will leak. It can damage the memory board. Also, the off gassing of it can cause corrosion in the main computer as well. I checked my Amiga a few months ago. It does have the A501, but mine is not fitted with a battery. The PCB has the "outline" for where the battery should be, but no battery. It doesn't look like it's been removed by anyone either (unless they did an exceptionally fine job ...). No idea why mine has no battery. Antonio -- Antonio Carlini anto...@acarlini.com
Re: Restarting Old Amiga's
I was very active in collecting, and on this list at the beginning. I also have a couple A1200’s that need work, and I used to have a couple A2000’s (those went to Eric Smith probably 15-20 years ago). There is also a partial A500, unfortunately I think it’s missing the keyboard, IIRC. Nice! My current Amiga list is an A500, A600 (under repair, I think I'm going to replace the fat agnus NTSC chip as a shot in the dark), A2500 (68020, 4MB, SD2SCSI, Toaster) and an A4000T (in great condition but I do need to recap it. Bought all the caps, not thrilled about the work ahead of me.) The memory expansion was purchased new, around ’98. I just removed it and checked it, and it looks fine. Ah cool! Good! Sounds like this belongs in the same category as my two A1200’s, namely needing some serious surface mount work. I know the one A1200 has an issue with a chip that overheats. One strange thing about the A600, it’s already half apart, I’m not sure why, as it worked just fine when I got it, and I’ve never gotten around to figuring out how to put it back together. I’ll give it a smell later today. :-) Yep, same issue. Does the overheating chip A1200 run? There are replacement motherboards for that but I don't think they pre-populate them with all the common parts unfortunately. That would be cool if they did. The A600 might of been apart for adding in a 44 pin IDE to CF card or something? That is an option that makes the A600 awesome. I’ve been aware of the A3000 battery issue, I believe that I resolved this on the original in the late 90’s. Pulling my spare A3000 out of the box, and checking it has been on my todo list for a long time. :-( My main A3000 has been nicely upgraded, and was even running AmigaOS 3.9, the last time I was using it. It’s one of two reasons I still have a 10Base-2 network segment (the other is my DECserver). For a few years, this was one of my main systems. Spare A3000 :-) If the batteries are removed from both you should be in a good position. About 5 years ago, I picked up a Gotek floppy replacement system, with the intention of putting it into the A500. Yea I have one of those with the community firmware and OLED screen in an external enclosure for Atari ST Mega 2 with bad internal floppy. They are useful and cheap. - Ethan -- : Ethan O'Toole
RE: VAXstation 3100 power supply
Peter, This is just generic advice based on recent experience. I would replace all electrolytic caps. I had some test pretty good, but PSU worked after I replaced them. Also check all the rectifier diodes as well, and I have had an opto-isolator fail. Dave > -Original Message- > From: cctech On Behalf Of Peter Hicks via > cctech > Sent: 08 June 2020 15:10 > To: cct...@classiccmp.org > Subject: VAXstation 3100 power supply > > Hello > > I have a couple of VAXstation 3100s - a M38 which boots but has no output > on the console port, and another model which has corrosion on the > motherboard and a PSU which doesn't power up correctly. > > The voltage on all of the M38 PSU's pins is OK except for pin 7 (brown) which > is +3.5v to +5.25v DC and is floating at about 0.6v with reference to ground. > I > suspect this is why the console port doesn't work (and the LEDs on the read > suggest a RAM problem so I can't tell which chip is faulty), so I've set about > troubleshooting. > > Does anyone have any suggestions above and beyond replacing capacitors? > > > Peter > > -- > > > OpenTrainTimes Ltd. registered in England and Wales, company no. > 09504022. > Registered office: 13a Davenant Road, Upper Holloway, London N19 > 3NW > > >
Re: VAXstation 3100 power supply
Hi Dave Superb, thanks - I hadn't thought about the rectifier diodes. A word of caution for anyone replacing the 470uF/250V electrolytics near the mains side of the board: the Nichicon like-for-like replacements are shorter and wider than the ones they replace and don't actually fit. Peter On Mon, 8 Jun 2020 at 15:30, Dave Wade wrote: > Peter, > This is just generic advice based on recent experience. I would replace > all electrolytic caps. I had some test pretty good, but PSU worked after I > replaced them. Also check all the rectifier diodes as well, and I have had > an opto-isolator fail. > Dave > > > -Original Message- > > From: cctech On Behalf Of Peter Hicks > via > > cctech > > Sent: 08 June 2020 15:10 > > To: cct...@classiccmp.org > > Subject: VAXstation 3100 power supply > > > > Hello > > > > I have a couple of VAXstation 3100s - a M38 which boots but has no output > > on the console port, and another model which has corrosion on the > > motherboard and a PSU which doesn't power up correctly. > > > > The voltage on all of the M38 PSU's pins is OK except for pin 7 (brown) > which > > is +3.5v to +5.25v DC and is floating at about 0.6v with reference to > ground. I > > suspect this is why the console port doesn't work (and the LEDs on the > read > > suggest a RAM problem so I can't tell which chip is faulty), so I've set > about > > troubleshooting. > > > > Does anyone have any suggestions above and beyond replacing capacitors? > > > > > > Peter > > > > -- > > > > > > OpenTrainTimes Ltd. registered in England and Wales, company no. > > 09504022. > > Registered office: 13a Davenant Road, Upper Holloway, London N19 > > 3NW > > > > > > > > > -- OpenTrainTimes Ltd. registered in England and Wales, company no. 09504022. Registered office: 13a Davenant Road, Upper Holloway, London N19 3NW
VAXstation 3100 power supply
Hello I have a couple of VAXstation 3100s - a M38 which boots but has no output on the console port, and another model which has corrosion on the motherboard and a PSU which doesn't power up correctly. The voltage on all of the M38 PSU's pins is OK except for pin 7 (brown) which is +3.5v to +5.25v DC and is floating at about 0.6v with reference to ground. I suspect this is why the console port doesn't work (and the LEDs on the read suggest a RAM problem so I can't tell which chip is faulty), so I've set about troubleshooting. Does anyone have any suggestions above and beyond replacing capacitors? Peter -- OpenTrainTimes Ltd. registered in England and Wales, company no. 09504022. Registered office: 13a Davenant Road, Upper Holloway, London N19 3NW
Re: Restarting Old Amiga's
> On Jun 8, 2020, at 1:24 PM, Ethan O'Toole wrote: > >> I have the urge to get my Amiga’s back up and running. I’m still trying to >> find my main Amiga A3000, but have found my A500 and my A600. The problem >> is, I don’t remember the last time I powered these on. It’s been a long >> time since I’ve had time. In the case of the A3000, I think it’s been about >> 17 years. My Atari TT030 has been even longer. :-( > > Nice collection! I was very active in collecting, and on this list at the beginning. I also have a couple A1200’s that need work, and I used to have a couple A2000’s (those went to Eric Smith probably 15-20 years ago). There is also a partial A500, unfortunately I think it’s missing the keyboard, IIRC. > So now for the bad news. > > On the Amiga A501 trap door memory expansion, there is a battery for the time > clock that will leak. It can damage the memory board. Also, the off gassing > of it can cause corrosion in the main computer as well. The memory expansion was purchased new, around ’98. I just removed it and checked it, and it looks fine. > the Amiga 600 has surface mount capacitors that will leak and eat the main > board. The machine will smell kinda funny, like fish or something. You will > want to pull it apart and investigate it. The caps are in the upper left, > upper right and middle for the most part. Have one on my bench I've been > trying to fix for a while and it's been tough. I advice recapping before > powering it on. And the cap job takes some work since it's all surface mount > and the solder is funky from the electrolyte corrosion. Sounds like this belongs in the same category as my two A1200’s, namely needing some serious surface mount work. I know the one A1200 has an issue with a chip that overheats. One strange thing about the A600, it’s already half apart, I’m not sure why, as it worked just fine when I got it, and I’ve never gotten around to figuring out how to put it back together. I’ll give it a smell later today. :-) > the Amiga 3000 suffers from a battery leak issue as well. Take it apart, clip > out the battery on the mainboard. It's under the drives if I recall. Check > the damage around the area. Look online for neutralizing it all on this and > the A500. There are replacement mainboards that have been produced if you're > adventurous and your board is no good anymore from extreme damage. You have > to solder everything on and move over parts. > > There are some killer upgrades for the A500 that give it ~40mhz, 8MB of RAM > and hard drive via SD or CF cards. These upgrades might run $150-$200, not > bad compared to the flash cards that cost $120 for many systems or say, the > CF disk only for the Apple II @ $120ish. I’ve been aware of the A3000 battery issue, I believe that I resolved this on the original in the late 90’s. Pulling my spare A3000 out of the box, and checking it has been on my todo list for a long time. :-( My main A3000 has been nicely upgraded, and was even running AmigaOS 3.9, the last time I was using it. It’s one of two reasons I still have a 10Base-2 network segment (the other is my DECserver). For a few years, this was one of my main systems. About 5 years ago, I picked up a Gotek floppy replacement system, with the intention of putting it into the A500. Zane
Re: Someone's confused
On 6/8/20 12:49 PM, ben via cctalk wrote: > But speed is relative. They changed computers where I was studing > electronics from a IBM-1130 to a VAX (something) in 1982. > I could use the IBM but the not VAX because they would have too > many users if that division had access to the VAX, and the > electonics section had PDP8 computers anyway. > So I suspect any VAX with one user would be faster than REAL > world machines in 1980's. > Ben. > PS:Virtual memory thrashing is what slows a computer down, > not say a 10,000 monkeys typing Shakespeare on ASR-33's. Well, one of the problems is the OS scheduling users without the ability to manage resources. There's nothing wrong with virtual memory, provided that it's managed correctly. When the illusion of lots of memory causes the scheduler to drastically over-commit resources, you get thrashing and nobody gets anything done. Although there are exceptions. I recall that it was possible, using large page sizes on the CDC STAR-100 to execute an instruction that could never get started. The STAR had 512KW (64 bits) of memory and a large page size was 64KW. A typical vector instruction could require 6 addresses for source, destination and control vectors. Put the starting address of any of these in last 8 words of a page and the hardware faulted preemptively for next page. It was kind of funny to watch; the P-counter for the user never budged, but the pager was sucking up time like crazy. I think someone eventually devised a check in the pager for this case, but I'm not certain. --Chuck
Re: Restarting Old Amiga's
I have the urge to get my Amiga’s back up and running. I’m still trying to find my main Amiga A3000, but have found my A500 and my A600. The problem is, I don’t remember the last time I powered these on. It’s been a long time since I’ve had time. In the case of the A3000, I think it’s been about 17 years. My Atari TT030 has been even longer. :-( Nice collection! So now for the bad news. On the Amiga A501 trap door memory expansion, there is a battery for the time clock that will leak. It can damage the memory board. Also, the off gassing of it can cause corrosion in the main computer as well. the Amiga 600 has surface mount capacitors that will leak and eat the main board. The machine will smell kinda funny, like fish or something. You will want to pull it apart and investigate it. The caps are in the upper left, upper right and middle for the most part. Have one on my bench I've been trying to fix for a while and it's been tough. I advice recapping before powering it on. And the cap job takes some work since it's all surface mount and the solder is funky from the electrolyte corrosion. the Amiga 3000 suffers from a battery leak issue as well. Take it apart, clip out the battery on the mainboard. It's under the drives if I recall. Check the damage around the area. Look online for neutralizing it all on this and the A500. There are replacement mainboards that have been produced if you're adventurous and your board is no good anymore from extreme damage. You have to solder everything on and move over parts. There are some killer upgrades for the A500 that give it ~40mhz, 8MB of RAM and hard drive via SD or CF cards. These upgrades might run $150-$200, not bad compared to the flash cards that cost $120 for many systems or say, the CF disk only for the Apple II @ $120ish. -- : Ethan O'Toole
Restarting Old Amiga's
I have the urge to get my Amiga’s back up and running. I’m still trying to find my main Amiga A3000, but have found my A500 and my A600. The problem is, I don’t remember the last time I powered these on. It’s been a long time since I’ve had time. In the case of the A3000, I think it’s been about 17 years. My Atari TT030 has been even longer. :-( Any advice about powering them up? Of course another fun challenge will be to figure out where on earth all my Amiga floppies are. Zane
Re: Someone's confused
On 6/8/2020 6:46 AM, Antonio Carlini via cctalk wrote: On 08/06/2020 13:02, emanuel stiebler via cctalk wrote: Guys be nice! That's the slowest VAX, right? In a small cabinet, I would take it, simply for that ;-) In terms of speed I think the MicroVAX I might be even slower, although whether you'd notice would be questionable! In terms of size the MicroVAX I is considerably more convenient. Antonio But speed is relative. They changed computers where I was studing electronics from a IBM-1130 to a VAX (something) in 1982. I could use the IBM but the not VAX because they would have too many users if that division had access to the VAX, and the electonics section had PDP8 computers anyway. So I suspect any VAX with one user would be faster than REAL world machines in 1980's. Ben. PS:Virtual memory thrashing is what slows a computer down, not say a 10,000 monkeys typing Shakespeare on ASR-33's.
Re: Someone's confused
On 2020-06-08 11:55, Chris Zach via cctalk wrote: > 4) The 11/730 could emulate pdp11 instructions, the MV1 could not. Come > to think of it I think the 730's floating point could do D,F,G,H while > the MV1 could only do D,F,G. IIRC, there were two versions of the MV I board sets with different floating points?
Old communications software
If any of you are looking for new in box Lantastic or Hayes Smartcom software, I have some for sale. https://elecshopper.com/Communications-Software-c47411005 Cindy Croxton Electronics Plus 1613 Water Street Kerrville, TX 78028 830-370-3239 cell sa...@elecplus.com -- This email has been checked for viruses by Avast antivirus software. https://www.avast.com/antivirus
Re: Someone's confused
On Sun, Jun 7, 2020 at 10:53 PM Jon Elson via cctalk wrote: > Hmmm, separate sentence, I think they are saying they have > VAX 6000's and VAX 730's available, > call for freight quote. Wow, who would want a 730? I would, but I already have one, so like Tony, I don't need *another* one. -ethan
Re: Someone's confused
I believe your recollection is correct. I was working on a project and looking at replacing a bunch of 11 boxes, and we had an NDA discussion of what would be MVII. WE selected those to replace the aging 11 boxes, the configuration gave us more compute nodes, less power consumption, and much less physical space needed to house the gear. Worked great for a long time. Of course later, the uVII boxes were consolidated into larger vax offerings, but combining the functions of multiple uVII boses. bb On Mon, Jun 8, 2020 at 12:51 PM Antonio Carlini via cctalk wrote: > > On 08/06/2020 16:55, Chris Zach via cctalk wrote: > > I have a MV1 board set here, I'd be willing to fire up VMS to see if > > it's slower if someone wants to send me a TK50 boot tape but I'm > > guessing it would be the slowest Vax on earth. > > > > Reasons why: > > 1) MV1 has only 4mb of memory to the 730's 5mb. > > > > 2) I believe the 730 accesses memory in 32 bit chunks as opposed to > > the MV1 having to access memory over the Q bus in 16 bit words. So > > you're double bucking there. Don't remember if the MV1 has a cache. > > > > 3) An 11/730 has that R80 controller. The R80 is most probably faster > > than the RQDX3+RD54, note that the RQDX3 is a slug of a controller > > compared even to a MTI ESDI controller. Possibly due to the MFM > > interface. > > > > 4) The 11/730 could emulate pdp11 instructions, the MV1 could not. > > Come to think of it I think the 730's floating point could do D,F,G,H > > while the MV1 could only do D,F,G. > > > > I'm not sure why they didn't do PMI memory on the MV1, possibly > > because it's two boards already and they might already talk over CD > > interconnect, limiting the memory to one card. But the result is a > > really slow little VAX, probably slower than the 730. > > > I think the MicroVAX I was (at least in part) built quickly to prove > that it could be done and was always intended to be superseded by the > MicroVAX II (which took longer and was more efficient). > > I'm sure I've seen explanations on the net before, but I can't find them > now. Maybe I read it on the EASYNET? In which case, until someone is > willing to release their backups of some of DEC's internal NOTES > conferences, we'll possibly never know. > > > Antonio > > > -- > Antonio Carlini > anto...@acarlini.com >
Re: Someone's confused
On 08/06/2020 16:55, Chris Zach via cctalk wrote: I have a MV1 board set here, I'd be willing to fire up VMS to see if it's slower if someone wants to send me a TK50 boot tape but I'm guessing it would be the slowest Vax on earth. Reasons why: 1) MV1 has only 4mb of memory to the 730's 5mb. 2) I believe the 730 accesses memory in 32 bit chunks as opposed to the MV1 having to access memory over the Q bus in 16 bit words. So you're double bucking there. Don't remember if the MV1 has a cache. 3) An 11/730 has that R80 controller. The R80 is most probably faster than the RQDX3+RD54, note that the RQDX3 is a slug of a controller compared even to a MTI ESDI controller. Possibly due to the MFM interface. 4) The 11/730 could emulate pdp11 instructions, the MV1 could not. Come to think of it I think the 730's floating point could do D,F,G,H while the MV1 could only do D,F,G. I'm not sure why they didn't do PMI memory on the MV1, possibly because it's two boards already and they might already talk over CD interconnect, limiting the memory to one card. But the result is a really slow little VAX, probably slower than the 730. I think the MicroVAX I was (at least in part) built quickly to prove that it could be done and was always intended to be superseded by the MicroVAX II (which took longer and was more efficient). I'm sure I've seen explanations on the net before, but I can't find them now. Maybe I read it on the EASYNET? In which case, until someone is willing to release their backups of some of DEC's internal NOTES conferences, we'll possibly never know. Antonio -- Antonio Carlini anto...@acarlini.com
WTB: 64K S-100 board, Hard Sectored 5.25" floppies
Looking for a CompuPro RAM 16 or something similar that will work in an IMSAI 8080. Also looking for a few hard sectored (10 sector) 5.25" floppies Reply off list! Thanks! - Ethan O'Toole
Re: Someone's confused
I have a MV1 board set here, I'd be willing to fire up VMS to see if it's slower if someone wants to send me a TK50 boot tape but I'm guessing it would be the slowest Vax on earth. Reasons why: 1) MV1 has only 4mb of memory to the 730's 5mb. 2) I believe the 730 accesses memory in 32 bit chunks as opposed to the MV1 having to access memory over the Q bus in 16 bit words. So you're double bucking there. Don't remember if the MV1 has a cache. 3) An 11/730 has that R80 controller. The R80 is most probably faster than the RQDX3+RD54, note that the RQDX3 is a slug of a controller compared even to a MTI ESDI controller. Possibly due to the MFM interface. 4) The 11/730 could emulate pdp11 instructions, the MV1 could not. Come to think of it I think the 730's floating point could do D,F,G,H while the MV1 could only do D,F,G. I'm not sure why they didn't do PMI memory on the MV1, possibly because it's two boards already and they might already talk over CD interconnect, limiting the memory to one card. But the result is a really slow little VAX, probably slower than the 730. C On 6/8/2020 8:46 AM, Antonio Carlini via cctalk wrote: On 08/06/2020 13:02, emanuel stiebler via cctalk wrote: Guys be nice! That's the slowest VAX, right? In a small cabinet, I would take it, simply for that ;-) In terms of speed I think the MicroVAX I might be even slower, although whether you'd notice would be questionable! In terms of size the MicroVAX I is considerably more convenient. Antonio
RE: Someone's confused
> -Original Message- > From: cctalk On Behalf Of emanuel stiebler > via cctalk > Sent: 08 June 2020 13:03 > To: r.stricklin ; General Discussion: On-Topic and Off- > Topic Posts ; General Discussion: On-Topic Posts > > Subject: Re: Someone's confused > > On 2020-06-08 02:35, r.stricklin via cctalk wrote: > > > > On Jun 7, 2020, at 7:52 PM, Jon Elson via cctech wrote: > > > >> Wow, who would want a 730? > > Somebody very, very determined. > > Guys be nice! That's the slowest VAX, right? > > In a small cabinet, I would take it, simply for that ;-) Yes, it is pretty slow. I used to use one in the mid 80's and I rescued the boards from it when it was about to be scrapped. I gave a couple of boards to someone who I don't think did anything with them in the end ☹
Re: Someone's confused
On 08/06/2020 13:02, emanuel stiebler via cctalk wrote: Guys be nice! That's the slowest VAX, right? In a small cabinet, I would take it, simply for that ;-) In terms of speed I think the MicroVAX I might be even slower, although whether you'd notice would be questionable! In terms of size the MicroVAX I is considerably more convenient. Antonio -- Antonio Carlini anto...@acarlini.com
Re: Someone's confused
On 2020-06-08 02:35, r.stricklin via cctalk wrote: > > On Jun 7, 2020, at 7:52 PM, Jon Elson via cctech wrote: > >> Wow, who would want a 730? > Somebody very, very determined. Guys be nice! That's the slowest VAX, right? In a small cabinet, I would take it, simply for that ;-)
RE: Someone's confused
> -Original Message- > From: cctalk On Behalf Of r.stricklin via > cctalk > Sent: 08 June 2020 07:36 > To: General Discussion: On-Topic Posts > Subject: Re: Someone's confused > > > On Jun 7, 2020, at 7:52 PM, Jon Elson via cctech wrote: > > > Wow, who would want a 730? > > Somebody very, very determined. > Well I would like one if I had the space. I might make space if one came up! > > ok > bear. > > -- > until further notice
Re: Someone's confused
On Jun 7, 2020, at 7:52 PM, Jon Elson via cctech wrote: > Wow, who would want a 730? Somebody very, very determined. ok bear. -- until further notice
Re: Malfunctioning VT240 - help please
On 07/06/2020 18:27, Charles via cctalk wrote: > Until a few minutes ago, my VT240 was operating normally, but now it's > unresponsive (fails during power-on self test). > > Normal behavior was: display a checkerboard, then two different > intensity all-white bands growing slowly up from the bottom of the > screen, then a beep and the expected "VT240 Monitor Error 9" (because > I'm using an old B&W composite monitor instead of the DEC VR201 with > special cable). Thereafter, normal operation. > > Now, it briefly displays the checkerboard (and all four keyboard > lights turn on, then off); then the Lock and Wait lights come on and > nothing else happens. Blank screen. > The keyboard LEDs are used to indicate the test being performed, in this case test 5 failed. They are listed in the pocket service guide. For the first 6 codes it just says fatal error, replace terminal controller board. I don't think it is the keyboard. You should get an error code 7 on screen for that. I'm afraid I haven't looked into the VT240 firmware but I have looked at the VT220 previously. Here are some of my notes on the self test: 0 = 8051 Internal RAM Test (Data=0xAA) 0 = 8051 Internal RAM Test (Data=0x55) 0 = 8051 Internal RAM Test (Data=0x00) 1 = 8051 Internal ROM Checksum (8840: lcall $8870) 2 = External ROM Checksum 0x8000 (884B: lcall $8870) 3 = External ROM Checksum 0xC000 8 = Screen RAM 0 (Addr=0xA000 Data=0xAA) 9 = Screen RAM 1 (Addr=0xA800 Data=0xAA) A = Atrrib RAM 0 (Addr=0x8000 Data=0xAA) B = Attrib RAM 1 (Addr=0x8800 Data=0xAA) 8 = Screen RAM 0 (Addr=0xA000 Data=0x55) 9 = Screen RAM 1 (Addr=0xA800 Data=0x55) A = Atrrib RAM 0 (Addr=0x8000 Data=0x55) B = Attrib RAM 1 (Addr=0x8800 Data=0x55) 8 = Screen RAM 0 (Addr=0xA000 Data=??) 9 = Screen RAM 1 (Addr=0xA800 Data=??) A = Atrrib RAM 0 (Addr=0x8000 Data=??) B = Attrib RAM 1 (Addr=0x8800 Data=??) C = Character ROM (read only) D = Alt Character RAM (read/write) E = Alt Character RAM (?) I know the VT240 uses a different processor to the VT220 but this gives you an idea of the sort of things that are being tested early on. I imagine the VT240 will carry out a similar set of tests. Matt
