test-drb January 2006

test-drb@ccmp.vtda.org

240 participants
511 discussions

General Discussion: On-Topic and Off-Topic Posts

by Billy.Pettit＠wdc.com

"Zane H. Healy" <healyzh at aracnet.com> wrote: I'm leaning more and more towards DIY, and have been threatening to buy a book or two on the subject (I've been thinking about the books by Morgan Jones, "Valve Amplifiers, 3rd Ed." and "Building Valve Amplifiers"). Part of it is the potential cost savings, and the other part is simply the challenge of building my own setup. I should have pretty much all the equipment I need, I just need parts. Zane There is a Dutch magazine with some valve projects that is worth your time to look at. Their projects are well documented. And they offer manufactured PCBs for everything they publish. I consider the magazine the best in the world for the electronics hobbiest. Magazine is "Elektor". It has an English edition, expensive, but worth it. Check their web site out. Seems like they had a few valve projects last year that may give you a lot of hints and ideas. And give you some sources of quality valves. Billy

18 years, 11 months

Compupro 8085/8088 switchover problem.

by dave04a＠dunfield.com

Hi Guys, Been working on my Compupro system over the holidays - got the 8086/8087 system booting CP/M-86 reliably finally (yeah!). Also have an 8085/8088 CPU that I am trying to get running. All other parts of the system are exactly the same config except that the boot ROM selection is (0) 8080 standard boot instead of (4) 8086 standard boot. The system starts in 8085 mode, and always boots CP/M 2.2 (8080) reliably. I have a couple of different 8/16 boot disks which have an 8085 first stage boot, which then switches to the 8088 and loads CP/M-86. So far I have managed to make the system boot CP/M-86 three times (and only three times) from two different disks in this configuration. In all three cases, once it booted, CP/M-86 ran reliably as well (I even tried tapping on the cards to detect physical problems, and it runs perfectly). On every other boot attempt (and there have been quite a few), I can observe the system load the first block (head load/unload), and then load another block (head load/unload) after which it goes silent. If I put in an 8086 boot disk (which would be "invalid boot code" to the 8085, the system dies after reading the first block - which suggests that it always gets at least part way into the boot cycle. My guess is that it is not transitioning into 8088 mode correctly. I've double checked the switch settings, and all matches the Compupro suggested configuration. Looking at the schematic, there is not a whole lot of circitry involved in switching from one to the other - I have removed, cleaned (chip and socket) everything even remotely related to switching the CPU to no effect. Next step is to begin tracing it with the scope, and trying to figure out exactly how far it is getting - I'm guessing it won't be an obvious "it stopped here"... This could be a little tricky to figure out. Just thought I would check here and see if anyone has experience with this system and can offer any ideas of likely things to check. Regards, Dave -- dave04a (at) Dave Dunfield dunfield (dot) Firmware development services & tools: www.dunfield.com com Collector of vintage computing equipment: http://www.parse.com/~ddunfield/museum/index.html

18 years, 11 months

DEC H967 cabinets and parts

by Useddec＠aol.com

I have some available, empty or with RK05 or RL01 or 02 drives. Also filler strips, feet, sides, etc. Thanks, Paul

18 years, 11 months

1802 problems

by ard＠p850ug1.demon.co.uk

Does anyone really know the RCA 1802 processor hardware? I am still debugging the microwriter, and have not got very far. I have an RCA user manual on the processor which seems quite comprehensive, I am asusming it's accurate. Now, according to that manual, the processor can be in one of 4 states (fetch, execute, interrupt responze, DMA), and which state it's in is output on 2 lines called SC0 and SC1. The INT/ line is high, both DMA IN/ and DMA OUT/ are also high. I can detect no gltiches on any of these signals. The clock is running, the bus looks active, etc. The problem is that I am getting active-high pulses on SC1. This, according to the data sheet means it's doing a DMA or interrupt response cycle. But why the heck should it? I thought it was a defective 1802 chip, but another one pulled from an old board shows identical behaviour (right down to locking up after typing 8 characters on the microwriter keyboard). I can't believe 2 have failed in exactly the same way. Unless of course this is a well-known problem. Any thoughts? -tony

18 years, 11 months

"Market" for old macs

by compoobah＠valleyimplants.com

Any decent hardware store (and some not-so-decent stores) will have long-shank T15 screwdrivers. I have even seen some longer interchangeable bits that might work. The upper screws are into plastic, the lower screws are into the metal frame near the logic board. All the ones I've taken apart have yielded to slaps on the side and shaking about 1" above a padded surface, but for a while some of the cheaper "Mac cracking" kits looked like they came with a "stationary clip" (the ones with the semicircular spring around sheet-metal jaws).

18 years, 11 months

Bitsavers mirror

by aek＠bitsavers.org

Al, with regard to bitsavers : is there a standard mechanism or approach to contribute material ? -- Depending on the size, either emailing it as an enclosure works, or if it's too big I can forward an ftp adr to use. 400dpi or higher B&W TIFFs using Group 4 FAX compression is the preferred format (or a PDF of same) though normally I convert everything that comes in to the tumbnail per page format that all of the other pdfs have for consistency.

18 years, 11 months

EPROM labels

by rcini＠optonline.net

All: Just a quickie.what would be a suitable replacement for the opaque labels that one would stick over EPROM windows? I was going to use electrical tape but it's so sticky and white mailing lables leave glue residue. Rich Rich Cini Collector of classic computers Build Master for the Altair32 Emulation Project Web site: http://highgate.comm.sfu.ca/~rcini/classiccmp/ /************************************************************/

18 years, 11 months

Free DECstation in Leeds, UK

by lproven＠gmail.com

Forwarded on, at his request, from an acquaintance of mine on the CIX online service: << Fwd: cix:obsolete/general:6745 tykepenguin(421) 29/12/2005 17:54 ---- Forwarded Message ---- DECstation free to good home Digital "Personal" DECstation 5000/25 25MHz MIPS processor 24MB Memory. 3 disks, one internal (and small). I can't remember the exact capacities, but I think the two externals are RZ56s No keyboard, mouse or screen. Runs Linux/NetBSD/Ultrix - will include Ultrix CD and licence. Collect from NW Leeds only. Patrick >> If you can't decode the header, the email address is tykepenguin at cix.co.uk. -- Liam Proven ? http://livejournal.com/userinfo.bml?user=lproven AOL/AIM/iChat: liamproven at aol.com ? MSN/Messenger: lproven at hotmail.com Yahoo: liamproven at yahoo.co.uk ? Skype: liamproven ? ICQ: 73187508 Gmail/Google Talk/Orkut: lproven at gmail.com

18 years, 11 months

PDP-11 booting, RL02 working!

by henk.gooijen＠oce.com

Thanks for sharing your work, Charles. I have a somewhat similar problem, but have not found time to investigate during the last holidays ... :-( I have 3 RL drive in one chain, and two come up "normal". The 3rd has the READY lamp on continuous, right from power-up. If I try to boot (from one of the other two), the READY lamp of that drive flashes once. Then the RUN lamp (on the 11/34) goes off. Checking memory shows that the first word at address 000000 contains 000240 (which is correct, AFAIK), but all next words are *written* 000000. Of those zeroes I am sure, because I filled the memory with 000005 before I tried to boot. So, from your story, checking the cable might be a good idea. And that is done in just a few minutes. BTW, somebody told me (long ago) that you better run XXDP with the WRITE-PROT button pressed (lamp lit) ...! Anyway, congrats on booting your machine! - Henk, PA8PDP. This message and attachment(s) are intended solely for the use of the addressee and may contain information that is privileged, confidential or otherwise exempt from disclosure under applicable law. If you are not the intended recipient or agent thereof responsible for delivering this message to the intended recipient, you are hereby notified that any dissemination, distribution, or copying of this communication is strictly prohibited. If you have received this communication in error, please notify the sender immediately by telephone and with a "reply" message. Thank you for your cooperation.

18 years, 11 months

Speaking of 6502s, was Re: 70's micros still available - was 1802 problems

by dm561＠torfree.net

Date: Mon, 2 Jan 2006 20:22:28 -0500 From: "Roy J. Tellason" <rtellason at blazenet.net> Subject: Speaking of 6502s, was Re: 70's micros still available - was 1802 problems >Speaking of 6502s, I happen to have a whole bunch of those, <snip> >Anybody know of some simple monitor-type software that's out there? <snip> -------------------------- AIM65? RS-232 interface, Assembler & ROMable BASIC available, lots of documentation, straightforward hardware if you leave out the on-board display, printer & cassette I/F: 6502, 6522, ROM/RAM & some TTL. >And, any suggestions for getting familiar with this stuff when most of my >8-bit thinking is the 8080/8085/z80 type parts? The idea of rom on top of >address space and that whole zero-page bit and only a 256-byte stack still >strike me as pretty strange... ROM on top of address space??? Thinking of a C64? Data sheets, lotsa books around... mike

18 years, 11 months

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test-drb January 2006