test-drb December 2016

test-drb@ccmp.vtda.org

156 participants
199 discussions

by fritzm＠fritzm.org

Hi folks: I've been thinking about trying some PDP-11 interfacing/emulation projects in the new year. I'd like to track down a an M105 address selector and an M7821 (or M7820) interrupt control to keep things simple to start with. Anybody have surplus of these they'd be willing to sell/trade? Thanks, and Happy New Year, all! ?FritzM.

7 years, 12 months

TI 990/189 debugging

by derschjo＠gmail.com

Hi all -- Got myself a TI-990/189 single-board computer based around the TMS9980 microprocessor (actually, a variant of it, the MP9529, which apparently differs only in that it has a lower maximum clock and only requires Vdd of 9.3V or so...) It was advertised as "it looks like it's working, but who knows" and so of course it arrived and it's dead. It powers up and nothing appears on the display, and the CR1-CR4 and SHIFT LEDs are illuminated. No response whatsoever. I've spent some time yesterday and today probing the thing and I think the CPU is dead, but I wanted to run it past the braintrust here in case anyone has any experience with the 9980... Here's what I see: Voltages are all nominal on the +12, +5 and -5 supply; +5 and -5 are present at the CPU, as is 9.3V for the VDD. At the CPU: - CKIN is clocking at the right rate, the phi3 clock generated by the CPU is also correct. - IAQ is not pulsing, so the CPU is not fetching instructions - The Address and Data lines are all zeros with no activity whatsoever - HOLDA is low, -HOLD is high (so the CPU is not being held) - READY is high - MEMEN is low (so no memory accesses are taking place) - INT0 through INT2 is 010 (which indicates that a LOAD interrupt is active, more on this later) I have verified that the POWERGOOD signal is going high after about a second after power-on, as expected (this causes things on the board to RESET appropriately). This in turn causes the -LOAD signal from the Power Up/Reset circuit to go low, which causes INT 1 to go high. (This is later supposed to be reset, once the CPU's IAQ line clocks after the first instruction is executed, but since that's dead, well, nothing happens.) Based on this, I believe the CPU to be faulty. Anyone have any thoughts on this? Given the VDD difference (12V vs 9.3V), I don't think a standard TMS9980 will work; the MP9529 seems to be difficult to source, but it shouldn't be hard to get 12V to the CPU... Thanks, Josh

7 years, 12 months

OS/8 FORTRAN IV

by chd＠chdickman.com

What happens when a PDP8/e executes an IOT to a non-existent device? My PDP8/e is skipping when it executes a printer flag test for a device that is not present. I tried the following FORTRAN IV program with OS/8 F4 on simh and it worked fine. C HELLO WORLD PROGRAM IN FORTRAN IV C WRITE(4,100) 100 FORMAT(" HELLOW WORLD!") END even with hello spelled wrong. When I tried it on real hardware it just hung. It looks like it is stuck in an interrupt loop. F4 uses interrupts for IO and has its own internal handlers. From the looks of it, there is an interrupt and it is not getting acknowledged. When the ISR returns, the interrupt is still there and it just loops. This is a PDP8/e and the INT BUS lamp is ON. I believe this means that the interrupt request line on the bus is true. I trace the program and it enters the ISR and checks a few flags. It finds the line printer char done flag set and then determines that it was spurious and returns, ignoring any other device that might be interrupting. I don't have any printer devices installed, so it is strange that is skips on the printer char done flag. When there is no device, what does the IOT do? I would expect a NOP with maybe AC corruption, but not a skip. In the ISR, the printer is checked before the TTY and I think the interrupt is from the TTY. -chuck

7 years, 12 months

How was the R80 (etc) HDA assembled?

by ard.p850ug1＠gmail.com

How was the R80 HDA put together at the factory? From reading the printsets, (R80, RA80, RA81, RA82 -- they all have similar HDA designs), I believe that the spindle and platters were assembled in the lower half of the 'clamshell' housing, then the upper part put on and bolted down. Then the positioner/heads were fitted via the front aperture and bolted in place. Then the head cables were plugged into the preamp board on the front cover, this put on the front of the HDA and fixed with the clips. All in a clean room of course. Looking at pictures of an HDA without the top cover (search for RA80 HDA on Google), I wonder how they fitted the positioner without damaging the heads. There are 2 heads per arm per side on an R80/RA80. There doesn't seem to be any way to insert a tool to keep them all off the platters. Or was there? Surely they didn't scrape them over the disk surfaces? Anyone know? I am not thinking of stripping mine, I am just curious.... -tony

7 years, 12 months

Transporting an LGP-30

by jnc＠mercury.lcs.mit.edu

> From: Cory Heisterkamp > this is likely as close as I'll ever come to having a first generation > machine Dude, as far as I'm concerned, if it uses some sort of circulating memory for main memory (either delay line or drum), it's pretty much first generation (of course, it all depends on how one defines generations). (Unlike the very similar - in size/cost/role - Bendix G-15, it doesn't have the 'next instruction' field in each instruction, to optimize performance, though...) Interesting factoid about the Bendix G-15: it was designed with the help of one of the ACE people (Harry Huskey), and is basically a re-packaged ACE with drum instead of delay lines. There's an interesting article by Huskey himself in "Alan Turing's ACE" (by Jack Copeland) which discusses the G-15. > From: William Degnan > I am being very careful not to call this "the first personal computer" Oh, I think a good case can be made. People often cite the LINC as the first, but the G-15 and LGP-30 were similar in cost and intent, albeit a generation (at least) older. Noel

7 years, 12 months

Banner Panels

by bob＠theadamsons.co.uk

> Date: Fri, 30 Dec 2016 14:10:05 +0100 > From: Pontus Pihlgren <pontus at Update.UU.SE> > > (re http://www.kcg.ac.jp/museum/computer/images/mini_computers/dec/vax11_780.jpg ) > > Yes, but it is the taller racks. I had only seen the metal header on > the PDP-12 and our 8/I with earlier lower racks. > > /P > My 1972 pdp-8/e has a metal header on an H960 tall cabinet. This was definitely original (I ordered and commissioned the machine back then). (Same one as the 8/I in the photograph - no model designation).

7 years, 12 months

DEC color standards was: Re: Banner Panels

by COURYHOUSE＠aol.com

In a message dated 12/30/2016 10:49:07 P.M. US Mountain Standard Tim, chd at chdickman.com writes: On Sat, Dec 31, 2016 at 12:21 AM, <COURYHOUSE at aol.com> wrote: > I wonder if there is a PANTONE color chat assignment that DEC > ever listed? That would allow you to nail it dead on. Of course it would, but the DEC STD 092 available is not specified in PANTONE, If a later version of the standard used PANTONE then it would be done because PANTONE is the defacto reference today. When did PANTONE become a standard? I saw the following... but that may have been a date for ink maybe not paint? Pantone, as it is today, was founded in 1962, when the company?at the time a small business which manufactured colour cards for cosmetics companies? was bought by Lawrence Herbert, who had been an employee since 1956. He immediately changed its direction, developing the first colour matching system in 1963. Herbert remains the CEO, Chairman, and President of the company. Ed# _www.smecc.org_ (http://www.smecc.org)

7 years, 12 months

DEC color standards was: Re: Banner Panels

by COURYHOUSE＠aol.com

In a message dated 12/30/2016 9:31:07 P.M. US Mountain Standard Time, chd at chdickman.com writes: On Fri, Dec 30, 2016 at 11:14 PM, william degnan <billdegnan at gmail.com> wrote: > You can add the industrial/11 blue and red to your color page That's another problem I think, there isn't any documentation to say what colors a particular scheme used. I think the PDP8/e is amber and terra cotta, but that isn't documented as far as I know. Your Industrial-11 was probably in Bicentennial colors. It sure looks like American Red, White and Blue to me. -chuck I wonder if there is a PANTONE color chat assignment that DEC ever listed? That would allow you to nail it dead on. Ed# _www.SMECC.org_ (http://www.SMECC.org)

7 years, 12 months

DEC color standards was: Re: Banner Panels

by COURYHOUSE＠aol.com

(with correction) I wonder if there is a PANTONE color chart assignment that DEC ever listed? That would allow you to nail it dead on. Ed# _www.SMECC.org_ (_http://www.SMECC.org_ (http://www.smecc.org/) ) In a message dated 12/30/2016 10:21:32 P.M. US Mountain Standard Tim, COURYHOUSE at aol.com writes: In a message dated 12/30/2016 9:31:07 P.M. US Mountain Standard Time, chd at chdickman.com writes: On Fri, Dec 30, 2016 at 11:14 PM, william degnan <billdegnan at gmail.com> wrote: > You can add the industrial/11 blue and red to your color page That's another problem I think, there isn't any documentation to say what colors a particular scheme used. I think the PDP8/e is amber and terra cotta, but that isn't documented as far as I know. Your Industrial-11 was probably in Bicentennial colors. It sure looks like American Red, White and Blue to me. -chuck I wonder if there is a PANTONE color chat assignment that DEC ever listed? That would allow you to nail it dead on. Ed# _www.SMECC.org_ (http://www.smecc.org/)

7 years, 12 months

Z-80 code question about a loop that depends on the contents of the refresh register

by ethan.dicks＠gmail.com

Hi, All, I'm disassembling a vintage program and ran across this bit of code that is causing emulators to hang... MYSUB: LD A,R JP M, MYSUB JR Z, MYSUB CP 0x65 RET M LD A, 0x32 RET I know plenty of 8-bit assembler (mostly 6502, 1802, and a couple others), but I'm by no means expert on the Z-80. It appears that this subroutine is spinning on the value of the refresh register if it's zero or negative, then if it's below 0x65, return the former contents of the refresh register and if not, return 0x32? If it helps, this is from a CP/M game. I'm wondering if this is some sort of randomizer or delay routine. So far, this loop hangs on all three emulators I've tried - simh's altairz80, simcpm010 for AmigaDOS, and EMUZ80 for Raspberry Pi. I'm guessing none of these environments emulate specific behavior of the Refresh register? Does anyone have any comments or insights about what this is really doing and what the right thing to do for emulators is? I can patch this if that's what's needed, but I'd like to understand it first. Thanks, -ethan

7 years, 12 months

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test-drb December 2016