test-drb April 1999

test-drb@ccmp.vtda.org

170 participants
1190 discussions

Program Challenge (was Re: z80 timing... 6502 timing)

by KFergason＠aol.com

In a message dated 4/19/99 4:12:54 PM Central Daylight Time, cisin(a)xenosoft.com writes: > I must be missing something here. 9 does NOT produce the longest string > < 10, 8 does. (IX v VIII), and 3999 isn't the longest string. > > 3888 would seem to produce: > M M M D C C C L X X X V I I I \0 > which is 16 characters, including null. > > BTW, what comes after M? Is it correct that in Roman numerals there can > never be 4 consecutive occurences of the same letter? (The original Y4M > "bug"!!!) > No. Apparently the modern usage of Roman numerals is different than the Roman usage. Romans were known to do VIIII to mean 9, and were not really consistent in their usage. Interesting article in the Houston Chronicle discussing this a couple of months ago. 1999 can be made at least 3 ways, so a decision had to be made on which way should be used. (Hollywood movies, etc) Kelly

25 years, 2 months

Repairing core (was Re: How scarce (valuable) is core for the PDP-8?)

by ethan_dicks＠yahoo.com

--- Tony Duell <ard(a)p850ug1.demon.co.uk> wrote: > > I kicked off this whole mess with... > > > > I have a chance to buy a 4kW core stack for the PDP-8/i (-8/L). It's > > more than I want to pay, $100. Then --- Tony Duell <ard(a)p850ug1.demon.co.uk> wrote: > > Well, I've not bought core for a few years, and I payed a lot less than > that. Me, too. > But I believe core is now soemthing of a collectable (alas by > people who are not going to use it :-() Sigh. :-P > [...] > > > OTOH, I do have a broken (20-30 fractured cores) -8/L stack that I've > > contemplated repairing. It's a parity stack, so I can scavenge wire > > and cores from the parity plane (or just use the parity plane intact > > as another bit, then use one pad of broken core to repair the other, > > less damaged pad of broken core). > What I would do : > > I'd buy the core at $100, since that way you do have the working 8K for > your PDP. Then I'd try to mend the broken core plane that you already > have. If you fail, well you still have a machine with 8K in it (you'd be > kicking yourself, I think if you couldn't fix the old core and couldn't > still get a replacement). It seems the prudent thing to do, I was mostly just writhing about having to pay double of what _I_ think it's worth. I was polling for a sanity check to see if my expectations were unreasonable, or if the expectations of those stick-it-on-a-bookshelf collectors were. > If you do manage to mend it (and I think it's possible to re-string > larger-sized cores by hand) These are fairly large... much larger than on a 4kW stack for the PDP-11/20, but that's a three-wire plane. > then either make a 12K machine (if you can do that)... Not inside the -8/i (massive backplane, room for CPU, EAE, 8kW core and lots of I/O options. The -8/L expansion box _might_ take a total of 8kW) > or sell one of the core units to another collector (and if $100 is > the going rate you could probably get that for it). Or, of course, keep > it as a spare. I vote spare unless the price of core soars by one or two orders of magnitude. > > of time spent, it's cheaper for me to work a few hours and earn the money > > that the core pirate wants; in terms of lessons learned, repairing a > > 30-year-old core stack would be a big thrill, *if* it worked. > > Sure. Fixing old computers rarely makes financial sense, but then hobbies > rarely do. If I were in this for the money, I wouldn't be in it for the money. :-) > But learning how to mend core memory is an interesting thing > to learn to do IMHO (if I had a broken core unit you can bet I'd be > trying to fix it...) Do you have an opinion on how historically accurate is reasonable to attempt? By this I mean that the parity plane (all by itself on a 3/4 empty PCB) has no damaged cores. If I move the sense/inhibit wires from its slot on the paddle boards, I can borrow them intact to act as one of the damaged bits, I can then disassemble the more damaged plane (or perhaps the less damaged plane depending on where the damage is easier to get to) and only have to repair _one_ plane. In short: more like the original - disassemble the parity plane, removing it from the stack, converting a 13-bit broken stack with 4 PCBs to a 12-bit working stack, or, disassemble a broken plane, swap the data wires from it to the parity plane, keeping all four PCBs inside the stack. The second solution seems to make more sense from an effort and safety standpoint, the first solution seems to me to be more "pure". Thoughts? -ethan _________________________________________________________ Do You Yahoo!? Get your free @yahoo.com address at http://mail.yahoo.com

25 years, 2 months

How scarce (valuable) is core for the PDP-8?

by ethan_dicks＠yahoo.com

--- Lawrence LeMay <lemay(a)cs.umn.edu> wrote: Someone else suggested: > > I'm not sure I do, either. Maybe he means Charles Lasner, a frequent > > contributor to alt.sys.pdp8 (aka PDP8-LOVERS) up until a few years ago? > > Bingo, Thats who I meant. Charlie is indeed most wise, if you can read through his reams of detailed answers. I have always found him to be a great help in ferreting out bizarre tidbits of trivia. Having been to his house in Queens, I can say that he does have quite the wide range of hardware knowledge, but I think even he would blanch at attempting to disassemble a core pad and scavenge the bits (literally) to repair a broken plane. I know I'm intimidated by the prospect, but I figure worst case I broke something that was already broken. I wish I had one of the stereo inspection microscopes that I used when I worked on the factory floor at a Lucent plant in Columbus. It has a sliding base and an optional pneumatic pedal to fix the jig in place. We used it to inspect solder fillets on SMT edge connectors for circuit packs (the AT&T name for a PCB) for phone switches. If I had one of those for a month, I could probably get the view necessary to attempt to thread hair-fine wire through the cores. I do have a Weller temp-controlled iron to avoid scorching the PCBs and I do have a 1/64" tip for it (normally, I use a 1/32" tip for general SMT rework). The only hard problem I have is how to test the memory without assembling the entire plane first (due to the interconnections between the diode matrix boards and the individual core plane PCBs). Someday, when I have better tools and *lots* of free time... -ethan _________________________________________________________ Do You Yahoo!? Get your free @yahoo.com address at http://mail.yahoo.com

25 years, 2 months

z80 timing... 6502 timing

by edick＠idcomm.com

I don't know why this has to be so complicated. There need to be constraints in order to ensure a level playing field, but since there are two related objectives, (1) to find out which of the two processors in the title of this message is "faster" and (2) to generate the fastest code for them for comparison. If people want to perform the exercise on other than these two processors, that's fine. It might show that the quality of the code makes more difference than the relative speed of the processor, which shouldn't surprise anyone. It wouldn't hurt, at least. It won't show what the fastest, leanest, most efficient, or any other comparative of the various ways of coding the problem would be for those two processors unless there's 1:1 mapping for the instructions, however. Having more attempts submitted will undoubtedly teach someone something and that's good. What it will also do, is show everybody more innovative approaches to solving the problem. Dick -----Original Message----- From: Fred Cisin (XenoSoft) <cisin(a)xenosoft.com> To: Discussion re-collecting of classic computers <classiccmp(a)u.washington.edu> Date: Sunday, April 18, 1999 5:20 PM Subject: Re: z80 timing... 6502 timing >> > >Sure! Let's have a driving contest to see who can drive the fastest, but >> > >first we all have to build our own cars. THAT MAKES AN AMAZING AMOUNT OF >> > >SENSE! >> > Shsssh! We're building a race track first. >> No, that's too simple. First we have to go terraform Mars so that we can >> build the race track there. We don't want to give anyone an unfair >> advantage by letting them race their cars in a familiar atmosphere. > >I'm having a little bit of difficulty with not being able to use modern >tools and materials for the metallurgy for building my engine. :-) >Will I have to build it on Mars, also? > >If you really want to see a drivers only contest, watch IROC racing (was >just on ESPN this afternoon) - a dozen identical cars, and in 40 laps, the >pack spread out to a few car lengths. The winner was a Pontiac. So was >the loser, and every other car in the race. I think that it is more fun to >watch an event where the vehicles differ. > >We really need two sections of the whole competition - one section with >fixed platforms, and one section permitting custom hardware. >

25 years, 2 months

IBM Optical drive questions

by SUPRDAVE＠aol.com

In a message dated 19/04/99 17:16:44 Eastern Daylight Time, roblwill(a)usaor.net writes: << My other question is if Optical disks are re-writable? I've talked to two people, and one of them says that Optical disks aren't re-writable, mangeto-optical disks are. The other person said that no optical disk is re-writable, and that only floptical disks are (isn't that a form of optical disk?) >> the type 3431 is rewritable. the 3363 is write once- read many.

25 years, 2 months

Program Challenge (was Re: z80 timing... 6502 timing)

by mbg＠world.std.com

>> You naughty _naughty_ programmer! That's not at all in the spirit of >> the competition! >> (Wish I'd thought of it.) > >shhhhhhhhhh! Now they'll try to plug up the look up table loophole. > >Y'know, if the rules don't SAY what it has to be, ... The rules don't say you can't... but you do have to account for all memory used, for code and data... I've coded a version for pdp-11s, but since I have yet to test it (though of course it will work first time :-) I'm not going to post it yet... It takes up 62 words (132 bytes), uses 4 words on stack and 9 words of pure data space... when I've actually gotten a chance to try it, I'll be able to report how many instructions it takes to do the conversions (I suspect '1' is minimum and 3888 is maximum). I don't know how to check on number of cycles, though... The algorithm is pretty straightforward... converting to Roman is the same as converting to decimal except that once you have the digit for a given power-of-ten place, you convert *that*... I wrote it before looking at the code which was posted, and I suspect the algorithm is similar with the exception that I don't have a lookup table for the digits... Megan Gentry Former RT-11 Developer +--------------------------------+-------------------------------------+ | Megan Gentry, EMT/B, PP-ASEL | Internet (work): gentry!zk3.dec.com | | Unix Support Engineering Group | (home): mbg!world.std.com | | Compaq Computer Corporation | addresses need '@' in place of '!' | | 110 Spitbrook Rd. ZK03-2/T43 | URL: http://world.std.com/~mbg/ | | Nashua, NH 03062 | "pdp-11 programmer - some assembler | | (603) 884 1055 | required." - mbg | +--------------------------------+-------------------------------------+

25 years, 2 months

Program Challenge (was Re: z80 timing... 6502 timing)

by yakowenk＠cs.unc.edu

] How much memory is used can be defined in two ways. (a) the number of ] bytes, and (b) how much contiguous memory must be present in order to allow ] the code to be implemented. It requires 200 bytes of RAM is not a valid ] statement if that RAM has to be scattered over a 32-KByte range. ... Worrying about using 32K? For a simple little Roman Numeral pro... uh... <* light bulb goes on *> You naughty _naughty_ programmer! That's not at all in the spirit of the competition! Bill. (Wish I'd thought of it.)

25 years, 2 months

How scarce (valuable) is core for the PDP-8?

by lemay＠cs.umn.edu

> When I mentioned the chance to buy a 4kW stack for the PDP-8/i for $100... > > --- Lawrence LeMay <lemay(a)cs.umn.edu> responded: > > > Actually, that's probably a reasonable price. > > Foo! Well, I didnt say that I would pay $100... Or that it was a great price. But it might be a fair price. Of course, If i didnt already have a bunch of core of various types, and if i needed it to restore a pdp8 system (which would be at the absolute top of my list to do, as the first computer I ever saw, and every used, was a PDP8/e) then I would probably pay it. And i'd be cursing at whatever the past 20-30 years had done to make the board not work anymore ;( And i'd probably try to locate Lassiter and see if my some miracle he could repair the board, etc. But, thats just me. To me, having a PDP8/e is the ultimate dream machine. That, and having the room to store a PDP8/e... -Lawrence LeMay > > > Core memory boards, probably non-working, have been going for a high price. > > I got sniped for a PDP-11 double-core stack this weekend, backplane included, > that went for $38, no reserve. > > > Age and a nice visible setup increase the price. > > The core stack for a PDP-8(i|L) is older than much of what's on the > market, but none of the good stuff is visible at all on it. > > > Now, I havent seen the memory in question. but the pdp8/e core > > memory i've seen is all covered by a clear plastic shield. This > > increases its value as a display piece, as you can easily see > > all the core, and its all protected. > > It's hard to describe the arrangement, but the core plane in question > here is a block with two edge-connectors on either side, "dual-height" > as they say, but it's much thicker - let's try bad ASCII art to illustrate... > > > ######## ######## > xxxxxxxxxxxxxxxxxx == ######## ######## > ######## ######## ######## ######## > > core planes paddle-boards with wire harness > > The outside of the core plane part is covered in a "diode matrix", with > a wad of twisted-pair wires that go off to paddle-boards, one for the > sense bits, one for the inhibit bits. The address lines come up the diode > boards, the data comes up and down the paddle-boards. > > There are several PCBs with core in the core stack, 4-bits per layer with > an optional parity layer that has one pad of bits and three pads of core-less > X-Y wires. None of this is visible when the plane is assembled, and it's > soldered together with lines of wires going up and down the planes. > > > Of course, in order to use the core on a pdp8/? you would need > > a couple of support boards in addition to the core plane board > > itself. I would say that just the core plane, being of a nice > > size, and being very good 'visually' to display, and somewhat > > because its a PDP8 series board (nostalgia value), that its > > probably worth $100 all by itself. If it comes with the 2 support > > boards and the top connector things at that price, then i'd say > > its a bargain. > > You are thinking of newer hardware. The pre-OMNIBUS 8's have a wad of > individual, single-height cards that contain the sense-amps and the inhibit > drivers. I have a pile of them from an -8/L that someone else had already > begun to strip for parts before I bought it (it also happens to contain the > only DEC lock that does *not* use the XX2247 key). I'm not worried about > the analog stuff... I need the core. > > Of course, as Allison pointed out, I could always stick in a lump of battery- > backed static RAM. I was contemplating building a wiring harness to adapt > an RX8E on the back of either an -8/L (which has 8kW of core out of 12kW in > an expansion cabinet) or on the -8/i. I would use berg connector pins to > stick the wires on the back side of the backplane (to avoid soldering, of > course; but worst case, I just wire-wrap on a connector or two and use > sheilded ribbon to move the signals around. > > The joys of restoration in a market of scarcity. :-P > > -ethan >

25 years, 2 months

Q-Bus and Unibus to ATA info

by clintw＠colorado.cirrus.com

> From pechter(a)pechter.dyndns.org Mon Apr 19 14:06:36 1999 > Reply-To: classiccmp(a)u.washington.edu > Sender: CLASSICCMP-owner(a)u.washington.edu > Precedence: bulk > From: Bill Pechter <pechter(a)pechter.dyndns.org> > To: "Discussion re-collecting of classic computers" <classiccmp(a)u.washington.edu> > Subject: Re: Q-Bus and Unibus to ATA info > In-Reply-To: <011101be8a92$47a92bc0$5d01a8c0(a)p2350.ecubuero> from emanuel stiebler at "Apr 19, 1999 12:27:26 pm" > MIME-Version: 1.0 > Content-Transfer-Encoding: 7bit > X-Phone-Number: 908-389-3592 > X-OS-Type: FreeBSD 3.0-Stable > X-Listprocessor-Version: 8.1 -- ListProcessor(tm) by CREN > X-Lines: 33 > > > > >On the other hand, I have been pondering the development of a ATA > > >drive controller that emulates MSCP (and possibly TMSCP). > > > > I'm sitting on the layout of one ;-)) > > > > Problem is, you pay appr 100$ license fee for MSCP, and another 100$ for > > TMSCP. > > > > emanuel > > > I'd pay $200 + parts for a board that would do MSCP and run my 11/23's > with an IDE drive. > > Actually, I'd love to find a SCSI or IDE controller with DEC OS support > for the QBUS. > > > Bill Take a look at the CQD-220/TM or CQD-240/TM at www.cmd.com. I have two CQD-240/TM that I bought recently (25-Jan-99) from Ficomp (www.ficompinc.com), that I am using in my uVAX II with Ultrix 3.1. These boards emulate MSCP and TMSCP. According to the technical manuals on CMDs website, these boards work in: LSI-11/23, PDP-11/23+, Micro-PDP-11/53, 11/73, 11/83, 11/93, uVAX II, uVAX III, VAX 4000 and DECSystem 5400 systems. They support RT-11, TSX, DSM-11, ISM-11, RSX, RSTS, VMS, UNIX, ULTRIX, and other operating systems which use DU/TU drivers. I am happy enough with the ones I have, I am going to buy a Unibus one for my 750 when it arrives. clint

25 years, 2 months

How scarce (valuable) is core for the PDP-8?

by ethan_dicks＠yahoo.com

I have a chance to buy a 4kW core stack for the PDP-8/i (-8/L). It's more than I want to pay, $100. My question is, what are these things going for these days? I don't really *need* it. The guy selling it has more core than this that he saved from a "recycler", but he's in it for the money, not out of a love for classic machines. Most of his memory, he sells to people who want something to stick on the shelf and "ooh" and "aah" at. :-( So... for those people who have been trying to get core over the past year or two, what's it costing? I'm trying to decide if I want to grab this stack to put into my -8/i and bring it up to 8kW, an entirely optional project (I have all the other parts I would need for the upgrade from a PDP-8/L that I got in 1982 that was sold as parts-only, bad core, and most of the I/O and part of the CPU missing). I think he's charging too much, but maybe I'm disconnected with the current pricing. I do know that if I pass on it, there are several other people who are waiting for this exact piece, so it'll be sold one way or the other when I answer him. OTOH, I do have a broken (20-30 fractured cores) -8/L stack that I've contemplated repairing. It's a parity stack, so I can scavenge wire and cores from the parity plane (or just use the parity plane intact as another bit, then use one pad of broken core to repair the other, less damaged pad of broken core). Any thoughts out there on core repair? It's 1968 DEC core with, AFAIK a seperate sense and inhibit wire, which is both good and bad - good because the cores are larger than three-wire core, bad because I'd have to thread up, down and two diagonals. Of course, I could always sell the broken plane to a collector and use the money to fund part of this working stack. So many options. In terms of time spent, it's cheaper for me to work a few hours and earn the money that the core pirate wants; in terms of lessons learned, repairing a 30-year- old core stack would be a big thrill, *if* it worked. Thanks, -ethan _________________________________________________________ Do You Yahoo!? Get your free @yahoo.com address at http://mail.yahoo.com

25 years, 2 months

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test-drb April 1999