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Livestream 10/21/23 - Liza Loop, Byron Stout, Wil Lindsay & Jim Hall - VCF's YouTube channel

by Jeffrey Brace

This Saturday, Oct. 21, 2023 at 6:30PM EDT, we will livestream to VCF's YouTube channel (https://www.youtube.com/@vcfederation) a talk with Liza Loop, Byron Stout, Wil Lindsay and Jim Hall. We will be talking about Educating today's children with vintage computers. We will take questions from the chat part of YouTube. Future livestreams: 11/4 - Jim Hall - Linux like Unix 11/11 - Liza Loop, Cynthia Solomon, Brian Silverman & Margaret Morabito - Educating students with vintage computers over the decades. I hope to see you there!

3 years

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PDP11 Dilog SQ706a SCSI Controller

by hupfadekroua

Hello all, are there some experiences to install as well as to configure a Dilog SQ706a QBus SCSI controller in a PDP11/73 successfully? The controller in question is working properly, that's executing the self as well as the host DMA connection tests successfully. The format procedure of a physical and of an emulated SCSI drive will be executed with success also. But how to configure the Dilog SQ706a as well as the 11/73 properly, so that the SCSI drive can be accessed as DU0. I'm using an SCSI RSX image on a ZULU SCSI emulator inherited from an 11/73 running successfully using a native DEC SCSI controller. I don't find any successful procedure on the web beside the manuals on bitsavers, which only can be seen as examples. A.

3 years

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M7846 RX11 Unibus floppy controller board documentation?

by Tom Hunter

I was unable to locate schematics and/or a maintenance manual for the Unibus M7846 RX11 floppy controller board. If anyone has these could you please scan them and make them available. Thank you. Tom

3 years

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IBM 5100 discussion

by Christian Corti

I have been pointed to the following discussion https://forum.vcfed.org/index.php?threads/ibm-5110-initial-info.1224000/pag… There, voidstar78 was apparently trying to contact me. Since my mail addresses are all functional (noone else had any problem with them, be it my personal or our museum's address), I wonder what he did, and I don't have a gmail address. I'm not on this forum, and I don't want to register to "yet another forum", so I can't even look at the pictures. But it seems to have been an interesting discussion. Pity it wasn't on this list. Christian

3 years

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Re: IBM 727 tape drive

by Len Shustek

At Mon, 18 Sep 2023 10:55:13 +0200 (CEST) Christian Corti <cc(a)informatik.uni-stuttgart.de> wrote: >as it will be soon of importance to us, I am seeking for the systems >engineering manual and drawings, well, everything about the IBM 727 tape >drive (not the 729!). I especially need the module locations charts and >the module schematics. Just a few weeks ago I donated to the Computer History Museum a set of 14 original IBM black binders of "Type 7xx" manuals from the 1950s, including the 727. That one is likely to be the same as what's on bitsavers, but since it's no longer in hand I can't check. They probably haven't made it through the CHM cataloging process yet.

3 years

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Obsolete Parts.... Unicorn Electronics

by D. Resor

I recently had a need for BC308 transistors. Of course those have been unobtanium for quite some time. My search beyond a distributor then went to eBay where I found Unicorn Electronics. More to the point I see from their website Apple 1, Apple ][ and Apple 1a Kits along with Apple 1 and Apple II parts are available. I thought some here might find this useful. https://unicornelectronics.com/ Don Resor

3 years

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Re: VT100: Failing 2114 Chip Replaced With One With The Same Fault

by Rob Jarratt

> -----Original Message----- > From: wrcooke(a)wrcooke.net <wrcooke(a)wrcooke.net> > Sent: 08 October 2023 04:15 > To: rob(a)jarratt.me.uk; Rob Jarratt via cctalk <cctalk(a)classiccmp.org> > Subject: Re: [cctalk] VT100: Failing 2114 Chip Replaced With One With The > Same Fault > > > > > On 10/07/2023 5:35 PM CDT Rob Jarratt via cctalk <cctalk(a)classiccmp.org> > wrote: > > > > > > I find this really hard to explain. It can't be the chip selection > > logic because then the addresses 0x2400-0x2407 would also fail and I > > checked the CS signal with the logic analyser just to be sure. I also > > checked the address lines directly on the RAM chip for any stuck bits > > and they seemed fine too. > > > > > > > > What are the chances of two 2114 chips failing at exactly the same address? > > Is there some failure mode I might not be considering? > > > > Rob > > Perhaps it isn't the 2114 or its associated circuit at all. Maybe some other > device is being incorrectly selected by that address and driving (half) the bus > low? Just a thought. Many thanks for the suggestion. This hadn't crossed my mind, so I checked. All the things that I could identify on the schematic that connect to the bus (UART, interrupt vector, flag buffer and modem signals) seem not to be enabled. I have looked at what is sinking the data bus, there is a buffer which seems to be OK and the 8251 PIC. The PIC is harder to check but I can see it is not selected and the input pins don’t appear to be shorted. Not really sure what else to consider. > > Will > > If you want to build a ship, don't drum up people to collect wood and don't > assign them tasks and work, but rather teach them to long for the endless > immensity of the sea. > > Antoine de Saint-Exupery

3 years

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List of DEC boards - Offers invited.

by Rod Smallwood

Hi I have had so many inquiries for the boards on my list its difficult to respond to them all. Please make an offer for what you want. Allow an additional minimum of $50 for UK to US shipping I'll keep the offer list open for a few days. Rod Smallwood

3 years

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VT100: Failing 2114 Chip Replaced With One With The Same Fault

by Rob Jarratt

I posted recently that I had identified a faulty RAM chip in my VT100 and having replaced it the terminal seemed to get further into the self test. After further analysis with the logic analyser I have realised that it is still failing the RAM test, despite an apparent change in behaviour. I think the change in behaviour could be simply due to the slightly suspect keyboard cable. But here is the puzzle. When I first identified the faulty RAM chip if found that address 0x2408 would read back as 0x0A instead of 0xAA. I reckon this equates to E50 in the schematic, as it is the upper nibble of the second bank of RAM. I replaced the chip with one I bought recently. It turns out the self-test is still failing at the SAME address. I find this really hard to explain. It can't be the chip selection logic because then the addresses 0x2400-0x2407 would also fail and I checked the CS signal with the logic analyser just to be sure. I also checked the address lines directly on the RAM chip for any stuck bits and they seemed fine too. What are the chances of two 2114 chips failing at exactly the same address? Is there some failure mode I might not be considering? Thanks Rob

3 years

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Re: How were 32-bit minis built in the 70s/80?

by Geert Rolf

Quote: > I could be remembering incorrectly but I think the Gould PN6080 mini we had exclusively for third year > comp sci at Macquarie Uni in the mid/late 80s was 32-bit made up of AMD2900 family logic (2901 ALU's). Find attached two pages of the CPU drawings of a Concept 32/67 and PowerNode 6000. Here the AMD 2901s show up. You remembered correctly! Geert Rolf owner of a PowerNode 6040 -- see https://geerol.home.xs4all.nl/DownLoad/UTX-paper.pdf

3 years

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