test-drb April 1999

test-drb@ccmp.vtda.org

170 participants
1190 discussions

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

by ethan_dicks＠yahoo.com

--- Allison J Parent <allisonp(a)world.std.com> wrote: > <Any idea how to estimate the gauge? > > You'll have to mic it once the diameter is known you can look it up give > or take the enamel insulation. OK. Can do. > <What size nuts? > > Small, looked like #2. Can you translate that to a size? I can imagine the size of a #4 nut (I have several). I can't clearly picture how big the O.D. of a #2 would be. > ...A good material for this is hypersil commonly used for transformers. Used for the windings or the core laminations? On the topic of core size vs switching speed, I'd always assumed the drive to minaturize core was driven by the economics of memory density. I never considered memory speed. -ethan _________________________________________________________ Do You Yahoo!? Get your free @yahoo.com address at http://mail.yahoo.com

25 years, 2 months

Old computer books for laymen?

by ds_spenc＠alcor.concordia.ca

Hi, I was just looking at some of the books I've collected over the years (trying not to study for the exam I have tomorrow morning) and I spotted an old book entitled "Teach Yourself Electronic Computers". It's from the Teach Yourself Books series, (c)1962 The English Universities Press Ltd. Other books in the series include "Teach Yourself Algebra", "Teach Yourself Arithmetic", "Teach Yourself Geometry", "Teach Yourself Atomic Physics" (<- I kid you not!) etc, so it seems to be a book for the non-geek. The book is actually pretty good! What other early computer books were there for the reasonably non-geekish? -- Doug Spence ds_spenc(a)alcor.concordia.ca http://alcor.concordia.ca/~ds_spenc/

25 years, 2 months

CP/M as an RTOS (was Re: Dumb OS question)

by allisonp＠world.std.com

<Which is not so much because CP/M or DOS actually is an RTOS (they aren't) <but that they don't get in the way of the programmer. The programmer is <free to write his own interrupt handlers, and even a task scheduler. < <Note that this very feature that makes such an OS potentially usable for <real-time systems is exactly what makes them poor choices as platforms <for general-purpose computing. Too much code gets written that works aroun <the OS for no especially good reason. < <Note that a "proper" RTOS both doesn't get in the way, *and* provides <useful real-time services. Which some old timers to comp.os.cpm may remember the firestorm when I called CP/M a file system and not an OS... ;) Allison

25 years, 2 months

about cdroms...

by rlaven＠shore.intercom.net

I have a couple Panasonic cdroms that work with an ISA soundcard. Full set of drivers and installation software also. -rob-

25 years, 2 months

IBM Optical drive questions

by roblwill＠usaor.net

Does the 3431 need a special type of disks, or do they all use the same type of disks? -Jason -----Original Message----- From: SUPRDAVE(a)aol.com <SUPRDAVE(a)aol.com> To: Discussion re-collecting of classic computers <classiccmp(a)u.washington.edu> Date: Monday, April 19, 1999 9:29 PM Subject: Re: IBM Optical drive questions >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 edick＠idcomm.com

> >> One other thing I'd say, though, is that it's perhaps a bit questionable >> publishing code as yet because it will pollute the idea pool (no reflection >> on the quality of the submitted code) in that those who read it over (which >> I haven't for that reason) will potentially have their own approach >> influenced by seeing someone else's. > >Or they'll find ways to improve on it, which is what gives this whole >seemingly pointless exercise actual meaning and purpose. > >Sellam Alternate e-mail: dastar(a)siconic.com >--------------------------------------------------------------------------- --- Careful now! What I find better may not be better to you. It depends on your goals and outlook. I'd have liked it better if the initial phase had been without code listings and description of the approach chosen. Nevertheless, there's not much harm done. One who wishes to be entirely original doesn't have to peek. Dick

25 years, 2 months

z80 timing... 6502 timing

by edick＠idcomm.com

It's called an epiphany, Sam. You know . . . a moment of clarity . . . goodness knows one seldom gets to enjoy such an event. Dick -----Original Message----- From: Sellam Ismail <dastar(a)ncal.verio.com> To: Discussion re-collecting of classic computers <classiccmp(a)u.washington.edu> Date: Monday, April 19, 1999 4:09 PM Subject: Re: z80 timing... 6502 timing >On Mon, 19 Apr 1999, Richard Erlacher wrote: > >> I don't know why this has to be so complicated. There need to be > >My god! Dick just had a revelation!! > >Sellam Alternate e-mail: dastar(a)siconic.com >--------------------------------------------------------------------------- --- >Don't rub the lamp if you don't want the genie to come out. > > Coming this October 2-3: Vintage Computer Festival 3.0! > See http://www.vintage.org/vcf for details! > [Last web site update: 04/03/99] >

25 years, 2 months

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

by edick＠idcomm.com

Your points are valid. I didn't intend building a new computer to be seen as a major construction project. It can be done with a processor, an oscillator can, a PAL, two memory IC's, and a UART, e.g. 16C450. As I said, it should take very little time, and the circuit could be built with both processors in the same circuit, perhaps with only one inserted at a time. It's not necessary, but it's the cleanest way to do the job if you want to participate yet haven't got a running system with one or both of these processors. By the way, if I were picking a processor for almost any job, these would be pretty far down the list, not because they're bad, but because others are so much more convenient. One other thing I'd say, though, is that it's perhaps a bit questionable publishing code as yet because it will pollute the idea pool (no reflection on the quality of the submitted code) in that those who read it over (which I haven't for that reason) will potentially have their own approach influenced by seeing someone else's. There ought to be a bit of time allowed to pass while folks contemplate the cosmic oneness and decide what they'll do. Dick -----Original Message----- From: Sean 'Captain Napalm' Conner <spc(a)armigeron.com> To: Discussion re-collecting of classic computers <classiccmp(a)u.washington.edu> Date: Monday, April 19, 1999 1:58 PM Subject: Re: Program Challenge (was Re: z80 timing... 6502 timing) >It was thus said that the Great Richard Erlacher once stated: >> >> Well, I recall that someone said, a while back, that the devil's in the >> details. > > I'll say 8-) > >> What I'm trying to do is place boundaries around this problem for >> purposes of understanding its limits. Others who attempt to replicate your >> work on other processors will want to know these things. From your >> statement that the process produces a result of '*' for an invalid input, >> which, apparently would include negative values, non-integers, and integers >> of value 4000 or greater. If the input is presumed to be unsigned integer, >> that solves much of the problem. Now, you want to store the output in >> memory, presumably as ascii characters, presumably as a null-terminated >> string, and perhaps (optionally) echo it to the screen in the aftermath of >> your run. Does that sound like a reasonable thing to do? > > Yes. The actual code being timed is the conversion only, not the output >part, which is why the conversion is being stored in memory. > >> How do we tell this program what string of numbers to convert? Is this >> someting you want to put into memory as a null-terminated string of binary >> values, or would you prefer a single word for each value, with a null >> terminating the input array or a fixed string length? > > Well, if it's extended to read in a Roman number and covert it to binary, >then yes, you read from a NUL terminated string. That way, you can test >both sides of the program. But that's IF it's extended. I've yet to see >anyone else offer any code for the presented problem. > >> > I liked Sam's suggestion of ``printing to memory'' as a way to avoid the >> >complications of I/O in this, and if I didn't make this clear that the >> >conversion was to be stored in memory, I'm sorry. >> >> That should work. In fact, input could be done that was as well, placing >> the input in memory and then executing the program from a debugger or with a >> call from a HLL. > > Which is why I specified that the conversion program be callable as a >subroutine---to isolate the program from the specifics of the operating >system/monitor used to test it. > >> > I'm a software guy---building computers isn't exactly my forte. Besides, >> >if I say my code only requires 200 bytes of memory, and I can't figure out >> >how to build a computer with 200 bytes of memory (pretty easy for me 8-) >> >then that means I have 56 additional bytes to play with, maybe by adding >> >code to run blinkenlights or something. >> > >> > Besides, who wants to build a computer for this? Okay, except for Tony? >> >> That's the ultimate test, though, isn't it? > > If (and it's a big if) I build a computer, it's going to be based on a 32 >bit chip minimum (like the 68k or ARM). And it's not going to be for this >contest either 8-) > >> >> How is the 6809E relevant to the timing of the Z-80 and 6502? >> > >> > Nothing at all, except as an outside reference. That, and I don't really >> >know Z80 or 6502 code (nor do I have development systems for these chips). >> > >> Its certainly an outside reference. It may be a challenge for everyone to >> improve on it. . . We'll see, I guess > > I'm sure a cycle or two can be shaved off here and there, but I haven't >gone back over it myself. Heck, I've yet to see anyone comment on the code >itself. > > -spc (Or are we having more fun discussing the problem than working on > it?) >

25 years, 2 months

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

by allisonp＠world.std.com

<Any idea how to estimate the gauge? I know I'd need red and green enameled <perhaps another color like yellow? I also wonder what they used to insulat <the splices? It appears to be some kind of paint. You'll have to mic it once the diameter is known you can look it up give or take the enamel insulation. <What size nuts? Small, looked like #2. <Oy! The core circuit that I copied for my 12th-grade drafting project use <7.5VDC as the half-voltage. How much oomph would it take to induce a stabl <magnetic pattern in a steel nut?!? I would think that enameled insulation <would cook right off the wire. Keep in mind using say 30ga wire and the current could be in the several amps range as it's a pulse (a big one!). The total time would still be short. For a practical example a suitable ferrite could be used and there are plenty of suppliers. To do it with steel (not iron) nuts you'd have to do some pulse testing using one and a single turn of wire to find the switch point (push it with a bipolar narrow pulse). a second wire (a few turns) can be connected to a scope. Increase the drive to the first wire until you see it start switching. the BH switch point will be noticeable if the core has usable hystersis (fails otherwise). A good material for this is hypersil commonly used for transformers. I think the cores of the late 50s used that with a dimension of 50mils OD and about 5turns of 0.1mil thick material. Large cores are less critical and give a bigger kick as a responding signal. The penelty is that large cores switch slowly and have really big half select currents. The latter is not a problem with modern semis but in the late 50s early 60s transistors that could switch fast were also too slow and tubes didn't switch high currents well. mades doing core very hard. A tidbit of design history extrapolated from design of the TX2 (an Electronics Design article). Allison

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 think I'd try to move the 'core mat' (cores + wires) from the parity > plane to the data plane and then repair the defective one. Not feasible. The X-Y wires run from one side of the PCB to the other and intersect two bits at a time, 64 cores each. It's not like a PDP-11 board (the only other one that I can look at right now). > Yes, it's a lot easier just to swap sense wires round, but that seems like > a kludge to me. I suppose I can start with disassembling the mat that seems easiest to get to, then decide on what to do with the parity bit from there. > I guess it comes down to : Do you need to _use_ this machine (when > swapping the sense wires round makes a lot of sense) or are you tryign to > restore it (when you make as few mods as possible). I have more than one PDP-8/L. I could always borrow a known good core stack >from an -8/L and stuff that in the -8/i. It's not as if our hobby depends on the provenance of spares as a "genuine" antique would. It's virtually impossible to guarantee that any particular part was *never* replaced over the lifetime of the machine. In order, I would like it to A) work, B) be aesthetic. A+B is optimal. A alone is acceptable. -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