test-drb July 2016

test-drb@ccmp.vtda.org

190 participants
243 discussions

by tdk.knight＠gmail.com

finaly got some pregress on this 8i from a feild restoration of mine.. now to sit down and do an order for the transistors and go talk to the local ewaste recycler on monday see if they can help me source some slider switches like one i found in the junk pile at the local hacker space last night looks very promising will need to get new rocker peics made to atach the 8i switches to but its looking promising if this works out there may be a suden suply of replacement switch assemblys avail... https://c1.staticflickr.com/9/8752/27863539914_a92d0264c7_b.jpg baby steps baby steps

8 years, 1 month

Nova 3 front panel

by jwsmail＠jwsss.com

Is there anyone with documents on the Nova 3 front panel, and what drives it? It has some number of custom DG chips, which hopefully are good if I want to try to fire it up to play, but am interested in that on good authority there are 28v incandescent lamps. A friend has an Eclipse front panel with nearly identical bezel, which has LED's and a number of differences in the logic (different connector to the system, for instance). So it is probably all run on 5v. I have not had time to figure out the driver circuit for any of the lamps to see what that may turn up, and wanted to know whether it was 28v lamps before I buy 40 of them. (the thing has only 2 out of a lot of lamps). Thanks Jim

8 years, 1 month

Possibly rarest Apple 1 ever for auction

by jnc＠mercury.lcs.mit.edu

> From: Corey Cohen > This board is from the 1st PCB house that made the "byte shop" boards > but has the more expensive and reliable RN sockets. Maybe someone at the 1st PCB house made an extra board for themselves, and used better sockets (since it was for themselves)? Noel

8 years, 1 month

Looking for HP 9810A keyboard springs

by iamcamiel＠gmail.com

Hi Guys, I've got an HP 9810A that has been stored in sub-optimal conditions by a previous owner; a lot of the keyboard springs have rusted away, so I'm looking for a replacement. These are about 15.5mm outer diameter, 0.35mm thick wire, about 10mm high when uncompressed, and have only about 1.5 turns of wire. Any pointers would be appreciated! Camiel.

8 years, 1 month

How to open a SUN CDROM drive box?

by mattislind＠gmail.com

I am probably too stupid to not understand how to get into this box: http://i.imgur.com/7KXKP2l.jpg Before I break some parts of the old plastic I better ask... What is the procedure to open this up? The drive doesn't seem to work properly. Either I need to get it working somehow or replace it with a new (512 byte block capable) drive. /Mattis

8 years, 1 month

WANTED: PDP-8 KE8E Extended arithmetic element

by anders＠abc80.net

>You used to be able to find a set with connector blocks for $200 to $300 >range on EBay. But I haven't seen any pop up for a couple of years now. > There are actually two individual board on eBay now, but the they are a bit expensive, ~$250 each. The freight change is about $200 to Sweden for each board (don't now if they combine chipping). I'll guess I have to pay for customs as well... >Keep an eye on machines. These options were found in the variants of E's >(F and M) and some A's. You might have to buy another machine in order to >get this option. > If I only could find one... >Remember that you are looking for what I would classify as a fairly rare >option on machines that are becoming rare now. There are not a lot of >these machines in service anymore. > >Good Luck! Thanks, I know that those things starts to get really rare. I could live with a broken set. /Anders

8 years, 1 month

Reproduction micros

by jnc＠mercury.lcs.mit.edu

> From: Paul Koning >> I always felt that RISC meant 'making the basic cycle time as fast as >> possible by finding the longest path through the logic - i.e. the >> limiting factor on the cycle time - and removing it (thereby making the >> instruction set less rich); then repeat'. > "Making the cycle time as fast as possible" certainly applies, in > spades, to the 6600. The deeper you dig into its details, the more > impressed you will be by the many different ways in which it does things > faster than you would expect to be possible. My formulation for RISC had two parts, though: not just minizing the cycle time, but doing so by doing things that (as a side-effect) make the instruction set less capable. I'm not very familiar with the 6600 - does this part apply too? >> RISC only makes (system-wide) sense in an environment in which memory >> bandwidth is plentiful (so that having programs contain more, simpler >> instructions make sense) I should have pointed out that programs of that sort take not just more memory bandwidth, but more memory to hold them. In this day of massive memories, no biggie, but back in the core memory days, it was more of an issue. >> One of the books about Turing argues that the ACE can be seen as a RISC >> machine (it's not just that it's load-store; its overall architectural >> philosophy is all about maximizing instruction rates). I looked, and it's "Alan Turing's Automatic Computing Engine"; in Chapter 8, "Computer architecture and the ACE computers", by Robert Doran (which is not, for some reason, listed in the ToC). > I think a lot of machine designers, though not all, were seriously > interested in making them go fast. Again, RISC has two legs, not just making the machine fast, but making them fast by using techniques that, as a side-effect, make them inscrutable, and difficult to program. The concept was that they would not, in general, be programmed in assembler - precisely because they were so finicky. Remember, the 801 was a combined hardware/compiler project, in which complexity was moved from the hardware to the compiler; and early RISC machines has things like no interlocks between pipeline stages. So they really were not intended to be programmed in assembler - the compiler was critical. The ACE, on the surface, didn't follow this, as it had no compiler. However, at a higher level, Turing definitely followed the RISC philosophy of making the machine as fast as possible, by using techniques that made it very hard to program; instead of moving the complexity to the compiler, he moved it to the programmer - the latter not being a problem, if you're Alan Turing! :-) Noel

8 years, 1 month

Multiflow Trace 14/300 close to being scrapped in Texas

by evan.linwood＠eastek.com.au

Hi All, I noticed that the Multiflow race 14/300 system listed on eBay didn't sell recently. I don't have any personal background with these machines but it seems they could be both significant and rare? It's been sitting on eBay but I wasn't sure if it had slipped between the cracks somehow? I've been in contact with the seller and he's said that he's still hoping to sell it, but that it has to be cleared soon (and would be scrapped). I don't live in the US, so it's not an easy one for me to work with. Is this of interest to anyone? Cheers Evan http://www.ebay.com/itm/112050410557

8 years, 1 month

OT: Scanner discussion board(s)

by hollandia＠ccountry.net

I need to find a place to ask questions about scanners (scanner in the sense of an Epson Perfection 1260 flatbed scanner, not in the sense of radios). Several searches have yielded only radio-type scanner sites (or dead links). Does anyone here know of newsgroups or discussion boards for scanners? Thanks, Kurt

8 years, 1 month

KT-24 and/or -11/24 backplane info

by jnc＠mercury.lcs.mit.edu

So I'm trying to work out how the PDP-11/24 memory works - in particular, how the memory slots in the backplane can also support SPC devices. Chapter 5 of the -11/24 Technical Manual does not help - irritatingly! It spends a lot of time talking about the CPU's memory mapping (well documented elsewhere), and little on these blasted busses! Alas, there seems to be no KT-24 prints online (although the tech manual makes reference to various pages in it); prints of the backplane would also be really useful, but again, don't seem to be in what is online. Does anyone have either one? Failing that, I guess it will require getting ahold of a backplane, and seeing what I can find out with an ohm-meter. In general, I am not absolutely positive about how the UNIBUS and the Extended UNIBUS manage to co-exist on the backplane (although I think I have worked it out - see below). The tech manual acts as if the KT-24 acts as an intermediary between the two... which is fine, except that how are the both carried on the backplane, separately, but at the same time? When there _is_ a KT-24 (the system can work without one - more below on this), how is the EUB (which is just the UNIBUS plus a couple of extra address lines) separated from the UB? The way the UNIBUS mapping registers work, the EUB address for any given cycle can vary from the UB address by an arbitrary amount, so lower address bits can't be shared between the two busses. (Because address bit X might have to simultaneously be '0' for one bus, and '1' for the other.) I.e. the two busses can't somehow mostly share the same pins, through some kludge... It appears likely that somehow the UNIBUS is on connectors C-F (i.e. where it normally is on SPC slots), and the EUB is on the A-B connectors (as in MUD slots) - and the two are not connected together. (Note that on the 11/24 backplane, 4 slots are marked "SPC/Mem", and two "SPC/MUD", which supports this theory; the 4 slots would have the EUB and the UB not connected together - as they would be in a normal MUD/SPC slot.) Looking at the CPU prints (which _are_ available), it appears to confirm this theory; the 22-bit EUB address bus is carried on the MUD/EUB address lines (connectors A/B), and the 18-bit UNIBUS addresses are carried on the SPC address pins (connector E). Dollars to donuts those pins are carried across slots 1-6, and not intereconnected vertically (I have yet to verify that, either with the backplane prints, or with an ohm-meter, but I would put a very large bet on it.) Oddly enough, the CPU uses the UNIBUS SPC data pins (connector C), instead of the MUD ones (connector A). The thing is that EUB memory boards (e.g. MM11-M - the relevant page of the MS11-P prints are missing from the online set, alas) pick up the MUD pins for data. So the backplane must connect together the SPC data pins and the MUD data pins. The system can apparently also work _without_ a KT-24! Which raises the question 'how do DMA devices get to the memory when there's no KT-24'? >From looking at the CPU prints, (pg. K11) it _looks_ like the UNIBUS is automagically mapped through to the EUB when there's no KT24 (there's a pin which is apparently pulled low by the KT-24); the low (256-8=248) KB of UNIBUS address space is mapped straight across to low address space on the EUB memory bus. With no KT24 in, a standard EUB memory can go in 2. Slot 2 is special, though; the KT24 needs not just the UNIBUS lines, and EUB address lines (to map from one to the other); it also has some special interconnects with the CPU, e.g. that 'UNIBUS adapter present' line. Guess I should document all this in the Computer History Wiki, but those prints (KT-24, and -11/24 backplane) would still be useful. Noel

8 years, 1 month

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test-drb July 2016