test-drb April 1999

test-drb@ccmp.vtda.org

170 participants
1190 discussions

by healyzh＠aracnet.com

25 years, 8 months

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

by cmcmanis＠mcmanis.com

At 03:27 PM 4/19/99 -0700, Sellam wrote: >Unfortunately, my rant is not going to stop the lame-o's selling it from >hyping it up as some cool collectable, and it's not going to stop the >techno-wannabees from buying it to stick on their wall. Recent experience, Them: "We have a PDP 8/F." Me: "Does it have any memory." Them: "We think so, there are six boards in the back." Me: (could be good, two core stacks..) "What are the numbers on the top?" Them: "Three are labelled G104 and the other three are labelled G227." Me: "No, you don't have any memory for this machine." --Chuck [For the record a 4K core stack in an 8 consists of a G104, G227, and H220 card. It was the H220 card that had the actual core "mats" on it. The H220 card is often "liberated" from PDP-8's as a trophy/display item.]

25 years, 8 months

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

by edick＠idcomm.com

-----Original Message----- From: Tony Duell <ard(a)p850ug1.demon.co.uk> To: Discussion re-collecting of classic computers <classiccmp(a)u.washington.edu> Date: Monday, April 19, 1999 6:44 PM Subject: Re: Program Challenge (was Re: z80 timing... 6502 timing) >> >> On Mon, 19 Apr 1999, Richard Erlacher wrote: >> >> > My best guess would be that off-the-shelf systems will be what folks use to >> > program for this "challenge" if anyone does it. There were so few tools for >> > homebrew or single-board 6502 systems that I doubt anyone with other than an >> > Apple or an OSI will be interested. OTOH, it will be someone running CP/M >> > or the like on a Z-80 who enters on the Z-80 side. >> >> That's a highly ignorant statement. There were plenty of other 6502 based >> machines, including the Commodore 64, VIC-20, the various Atari 800 >> models. It's an ignorant statement, perhaps, as my kids had all these "video toys" at one time or another, but not made from total ignorance. I intentionally have ingnored them because they had integrated video, which makes it less than trivial to assess whether you're getting all the available bandwidth and also makes it unlikely you'll find a compatible Z-80. Remember, it was the goal at the outset to make a comparison of the two processors unencumbered by "special purpose" features. >Don't forget the BBC micro either. IMHO it was one of the best 6502 >systems ever (although it lacked internal expansion slots, which was a >pity). The BASIC was the second-best I have ever used (beaten only by >BASIC-09), and it has a built-in 6502 assembler. > >Now there's a thought. There was an option for the BBC micro that was a >Z80 second processor (it's not that rare either), clocked at 4MHz (IIRC). >The BBC's 6502 clocks at 2MHz most of the time, slowed down to 1MHz for >some I/O. Now you can compare the Z80 and 6502's speeds in the same >machine, simultaneously. This might be an excellent system on which to make a real comparison. It might even be one on which to run that matrix multiplication problem I proposed last week. I thought that would be good because it would require the machines to keep running for a week or two. It also would really show the difference in terms of time since it's such a big job. Of course mass storage would be a requirement for that. Commodore also made a dual processor machine, didn't they? A Commodore-128, I seem to recall . . . The power supply from the thing now powers a nicad charger . . . Dick >-tony >

25 years, 8 months

core stacks

by jlwest＠tseinc.com

ISTR that if you had a core set for an 8 that was "mismatched", the hardware handbook had the procedure for using a scope to "tune" a set into the appropriate range. Jay West

25 years, 8 months

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

by dastar＠ncal.verio.com

On Mon, 19 Apr 1999, Ethan Dicks wrote: > > 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. I don't see what the big attraction to a core plane is. You stick it on your wall. Whoopee! Look at me, I have a core plane on my wall. Big fricken deal. Nobody even knows what it is anyway. From afar it looks like a black square. Closer up it looks like a piece of a window screen. Unfortunately, my rant is not going to stop the lame-o's selling it from hyping it up as some cool collectable, and it's not going to stop the techno-wannabees from buying it to stick on their wall. 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, 8 months

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

by edick＠idcomm.com

This is a valid viewpoint, though I think, ultimately, the question to be answered pivots around which processor was potentially the most efficient of all its resources, including time. However, just the raw speed got a lot of discussion. In 1983, the 4MHz 6502 was "old hat" and the 8MHz Z-80H was readily available. However, AFAIK the peripherals for the Z-80H were not, and, in fact, I didn't ever see them. Somebody said they were out there at some point, but I've never seen them offered for sale. You could, of course, postulate that a given processor could be run at a given rate, whether it's true or not, but if you want a comparison of REAL parts running REAL code in a REAL environment, then you need something more than if you just look at what various vendors sold. Every design has compromises made, and, back in the early '80's, cost of memory was a factor, as was the assembly cost. In general, I saw lots of boards for lots of different processors designed to make the most efficient use of memory. Once we have a good idea of what you're trying to measure, you can make adjustments to the system variables. If you want to compute how fast a processor runs code with a given-speed-rated memory, you've got to design the most efficient memory interface you can and then adjust the processor clock for that. If you merely want to use a rate which trivially provides a baud rate generator with a convenient harmonic of the baud rate you intend to use, you can, I suppose design for that. I made the statement that it would take, at most, a couple of days to build a system which would allow straightforward programs to be run and thereby satisfy the requirement for a test system. I didn't really intend that people build a unique system just for this test. What I figured was that folks could look around the basement and see what they could find that would meet their needs. An old Apple-II would work if you compensate for its obtuse timing. Since they all seemed to have a serial console, almost any S-100 system would work. It's pretty hard to imagine how a limitation like your suggestion would apply. Newer processors addressed weaknesses in the older ones. One of those was ease of programming. In some cases, e.g. the 6809, the processor was designed with a regular instruction set and lots of addressing modes so as to make generating code easy. It didn't necessarily make it faster. I don't know how elegant such code will ultimately turn out to be. My best guess would be that off-the-shelf systems will be what folks use to program for this "challenge" if anyone does it. There were so few tools for homebrew or single-board 6502 systems that I doubt anyone with other than an Apple or an OSI will be interested. OTOH, it will be someone running CP/M or the like on a Z-80 who enters on the Z-80 side. That was why I thought a good simulator would be the best solution. Dick -----Original Message----- From: Bill Yakowenko <yakowenk(a)cs.unc.edu> To: Discussion re-collecting of classic computers <classiccmp(a)u.washington.edu> Date: Sunday, April 18, 1999 5:21 PM Subject: Re: Program Challenge (was Re: z80 timing... 6502 timing) >You'd normally expect that the winner of any such contest would be >the most recent processor, wouldn't you? So, if the cut-off date >was 1982, any processor that was released in late '82 should probably >beat any that was already available in 1979. Of course, if the 1979 >processor had a much faster version available in 1983 (like a higher >clock rate), that faster version wouldn't be legal with the 1982 cut- >off, because that wasn't around in 1982. > >So, I suggest that one way of judging cleverness of software hacks >is that they let an older processor beat a newer one. > >Judging that way, we don't even need a cut-off date. But anybody >coding for a 1999 processor won't have any way to win. > >Of course, then we need clear evidence when each processor became >available at each clock speed, and we can argue about when the chip >was *really* available (as opposed to being orderable, or just having >the spec available). > > Bill. > >

25 years, 8 months

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

by ard＠p850ug1.demon.co.uk

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25 years, 8 months

z80 timing... 6502 timing

by edick＠idcomm.com

Yes . . . of course, I wasn't the one who thought a graphic display would be "nice" so one could see what was going on. 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 4:10 PM Subject: Re: z80 timing... 6502 timing >It was thus said that the Great Sellam Ismail once stated: >> >> 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!! > > Now now ... > > -spc (No need to overly sarcastic here ... 8-) >

25 years, 8 months

Ancient disk controllers

by edick＠idcomm.com

I think I said some of the part numbers were badly managed in this set of products. It's quite confusing when you're ordering. I definitely ordered the board with the 1010 chip on it, knowing that it would physically fit my application, only to have the 1000-05 with the 8x300 and 1100 chipset arrive. These chips, (the 1100's) were really just msi parts easy to turn out while they tested the functions separately. The project was so far behind that they had to do something to recover costs. The 2010 chip wasn't available for quite some time. It was the version with the ECC capability built in. The 1010 was the one used in the PC, though, since it was available. By the time the 2010 became available, the RLL scheme used in the 5010 and other LSI's (from other vendors) became popular, and the ECC capability was ultimately not exploited via the 2010 in a PC application. Dick -----Original Message----- From: Tony Duell <ard(a)p850ug1.demon.co.uk> To: Discussion re-collecting of classic computers <classiccmp(a)u.washington.edu> Date: Monday, April 19, 1999 3:33 PM Subject: Re: Ancient disk controllers >> The functional differences were that the -05 versions were physically >> smaller (5.75 x 8 inches) and didn't support the 8-inch drives. Someone >> else pointed out that the WD1000-05 uses the WD1010 integrated controller >> rather than the 8X300 and the WD1100 chip set. Since the main difference >> between the WD1000 and WD1001 is that the latter supports ECC, I would guess >> that the WD1001-5 must use a WD2010 controller. > >The WD1001-05 uses the older chipset (or at least mine does). It uses the >WD1100-06 ECC/CRC logic chip rather than (I guess) the WD1100-04 CRC chip. > >The WD1001-05 is based on the 8x300 + control ROMs, and not a WD1010. > >-tony >

25 years, 8 months

z80 timing... 6502 timing

by edick＠idcomm.com

While what you say is certainly true, the page-zero usage is not dynamic, so, unless your task is very large and complex, page zero usage is therefore under the coder's control. I agree with your observation that the rate of memory usage is a good indicator of the rate at which a processor gets work done. The 6502 shines in that respect, in that the internal operations are generally overalpped with the fetch of the next instruction, with a few notable exceptions. Generally speaking, I've chosen processors with foreknowledge of what the device's most frequent tasks would be. For example, I picked a 65C02 for an application for which my boss had expressed a profound preference for the Z-80. I had to prove to him that, for OUR task, the 65C02 had a couple of features we could use very effectively and which the Z-80 didn't offer. It's always case specific. Dick -----Original Message----- From: Dwight Elvey <elvey(a)hal.com> To: Discussion re-collecting of classic computers <classiccmp(a)u.washington.edu> Date: Monday, April 19, 1999 2:55 PM Subject: Re[2]: z80 timing... 6502 timing >"Richard Erlacher" <edick(a)idcomm.com> wrote: >> 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. > >Hi > I always have to wonder about the meaning of faster. >Although I like the 6502 for a lot of things and would >say that it is often faster than a 8080 for many things, >I also know that resources like page zero get used up >quickly. Once these are gone, things tend to slow down. > I think we will continue to see that, like in the past, >most processors with about the same memory access speeds >will do about the same amount of work ( same bit count ). >On chip cache has changed that some but that just makes >another category. I would say any processor was superior >to another on small benchmarks unless the numbers were >in the 5X magnitude or more. Large application are more >useful in comparisons but it is hard to come up with >enough cross platform examples to make meaningful judgments. > I've always said, one should stick with what makes you happy. >Dwight >

25 years, 8 months

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test-drb April 1999