test-drb November 2000

test-drb@ccmp.vtda.org

197 participants
507 discussions

by ajp166＠bellatlantic.net

From: Iggy Drougge <optimus(a)canit.se> >>You serious? Get real. Chipset, bah! I'm talking about pre chipset >>stuff of >>CDC Cyber and Univax1180, PB250. > >Univax never made pong machines to the best of my knowledge. ;-) No but spacewar on the 1180 was not to bad. >I can't say that I've ever encountered such a system. And what would the >applications be? HP pocket clacs, Microwave ovens, quite a few games, small army of control aps. Allison

24 years, 2 months

Wanted:TRS80 mod III/IV floppy controller or floppy kit

by claudew＠sprint.ca

Hi Finally picked up a TRS80 mod III for a realistic price. The first home computer I used when I was 15-16. It feels great... Works 100%, bright no-burn tube, 48k. Except for little bit of silver finish off front of keyboard, this unit is perfect. But, it's a no floppy system... I am looking for the floppy disk kit (including floppy mounting bracket if possible) or just a controller or even the controller schematic for a mod III or IV...Would probably install external floppies to keep case in original shape rather then make-up a mounting bracket for the drives if I cant find one... Thanks for reading Claude

24 years, 2 months

HP 85 available

by r.stek＠snet.net

If anyone is interested, I have an HP 85 available. It works intermittently - it's nothing that re-seating the chips in their sockets fixes! The printer works - don't know about the tape drive. I can pack it, but you will need to pay shipping (and promise to send me your next 'extra' Altair <g>). I can also throw in a new roll of thermal paper (besides the remainder of what is in the unit). I'm near Hartford, CT. email me privately with any bribes. Bob Stek Saver of Lost Sols

24 years, 2 months

Intro and Nixies

by ajp166＠bellatlantic.net

From: J Forbes <jforbes(a)primenet.com> >It had been sitting outside, and was not in very good >condition...but I pulled the display board out, and it seems to >be usefull (see link above for a pic). If you want to drive >Nixies from a TTL BCD signal, just score some 74141 type >devices, they were made for the task! I would also comment that there is a great deal of test equipment that use nixies that with maintence last for many years. My Yasu 350mhz counter is still going and it's 26 years old. Nixies have a good life. However 74141s are getting scarce. >basement, and found a Motorola 6802, 1982 vintage. I wonder if >it's usefull? Why not. I just finished an ELF (using nwer parts) and my CDP1802 chip from 1979 is still good. Allison

24 years, 2 months

TRS-80 Model 100 to Macintosh

by owad＠applefritter.com

Does anybody have any experience hooking a TRS-80 Model 100 up to a Mac to exchange files? I have the serial cable and the null modem adapter and I've tried both ClarisWorks and ZTerm, but I just can't get the two to talk. Can anybody offer advice? Thanks, Tom Applefritter www.applefritter.com

24 years, 2 months

Off topic but interesting?? Magnetics

by xds_sigma7＠hotmail.com

Maybe DHL is flying Junkers Ju-52's or C-47's or maybe even Ford Tri-motors? Bizarre... _________________________________________________________________________ Get Your Private, Free E-mail from MSN Hotmail at http://www.hotmail.com. Share information about yourself, create your own public profile at http://profiles.msn.com.

24 years, 2 months

Homebrewing a digital computer

by ajp166＠bellatlantic.net

From: Kevin Schoedel <schoedel(a)kw.igs.net> >Sorry, I didn't express myself clearly. In Chuck's machine the >displayed value comes from a 12 line I/O bus. He could build two >different display devices to attach to the bus: one for everyday use, >with LEDs and bcd-to-7-segment decoders, and one special occasions, >with decoders and drivers and sockets for the nixie tubes that he >borrows from whatever machine they otherwise belong to. You can but nixies are a pita to drive. Of era lamping would be bulb per bit. cheaper too. >Yes, he could make 4xx an encoded operation (like pdp8 operate >instructions) such that 400 happens to perform a clear. Or he could >make 4xx load the accumulator with 0xx, so that 400 is again a clear; >this may fit the spirit of the design better. In either case he need >not disclose the extra features at first :-) Exactly. Or the feature could be enabled/disables using a OPR like instruction. >Yes. But since I'm doing a pure 8-bit machine, including 8-bit memory >address, it's *already* limited significantly. I do currently have one >unassigned opcode, so I could add an I/O instruction if it turns out I >have enough board space. More likely I'll just move on to design #2, >where I can hide complexity in microcode. You'll find it doesnt hide. The features grow to increase complexity. ;) > >Yes, I'm still considering something like that, though I'd probably >keep it simpler, and just leave the PC in the accumulator: PC->AC, >MA->PC. I know this probably seems absurdly stripped down to anyone who >already knows what they're doing, but I don't, so I want to keep the >control very, very basic, to reduce the chance of serious errors. Not an unreasonable way. Worth considering as it has good register economy. >I think you're right. I know my current addressing scheme is too >complicated, and I no longer know why I've been so reluctant to give up >page 0 addressing. With say n-bit word and n-bit indirect address page 0 is more efficient but not required. What it does do for short words like 8bit it eats a bit that could be an address. >Do you have any comment on PC-page (upper bits from >PC, lower bits from instruction) versus PC-relative (PC + lower bits >from instruction, either sign extended or not)? Both work. If you're using an indirect address (like PDP-8) then go with PC-page as it much simpler. PC-relative is ok but requires an adder (or more gating to reuse the only adder). If there is one trick to keeping things simple, the fewer paths and gating of things will help simplify. Allison

24 years, 2 months

RX02 drive emulation (was RE: Lisa Profile Drive emulation on a PC)

by ajp166＠bellatlantic.net

From: Eric Smith <eric(a)brouhaha.com> > >I don't have documentation, so I'm not disputing that, but this >makes me very curious. How is it that the RX8-E card (M8357) can deal >with any of: > >1) RX01 >2) RX02 in RX01 mode >3) RX02 in RX02 mode The board has dual interface modes. The RX02 has multiple modes as well. The best way to no results is to try a RX02 in a Qbus box with RX01 controller. Made that error once, wasted a lot of time even though it hurt nothing. >From the standpoint of building a machine from the ttl ground up the RX01 drive controller is a great example of what can be done with little. Instruction set is: WBS (wait, branch, stall IO) DO (do pulse, xx,xxxx bits) JMP (to field X) CBR (conditional branch) It's mildly horizontally code and also verticle coded. Uses 74181 (x2) for the 8bit alu and a pair of 7489s for registers. instruction word is 8bits. Ran fast enough to decode/encode FDC data in real time. Allison

24 years, 2 months

Homebrewing a digital computer

by ajp166＠bellatlantic.net

From: Kevin Schoedel <schoedel(a)kw.igs.net> >Neat. I occasionally spend a little time working toward building myself a >simple processor. My priorities are rather different, though; I want to >make the 'moving parts' visible as far down as is practical and >affordable (which for me will probably mean SSI TTL, except for the >memory), rather than to make the programming model simple. In the end buildability means a simple machine, not always a simple programming model. >Could one build "nixie tube emulators", for instance using seven-segment >LEDs, and then borrow real ones from some other device for special >occasions? No. Nixie is one of 10 output (highvoltage very low current) and 7Segment is different in every other way. For an era machine 7 segment using incandescent lamps would be valid! > >>4 - CLEAR >> Reset the accumulator (and flags). >> Example: 400 - clears the state of the machine. >> Note: This seems a waste of a major opcode. > >I've tentatively decided that I'll go for a store-and-clear operation, ? >la EDSAC and PDP8, since, in the few sample programs I tried, the value >in the accumulator was still needed after fewer than half the stores. >This might conflict with your goal of simplicity, but on the other hand, >the question of how to retain (regain) the accumulator after a store >might make a good 'Exercise 1'. PDP-8 or the PDP-5 are a good example of minimal but useful instruction sets. PDP-8 savethe AC and store is done one of two ways. You can use the MQ but that requies three locations. SWP DCA N SWP The tighter version is also compatable across all the PDP 5/8 series. CLL DCA N TAD N Three words still but doesn't use a register that may not exist. >Alternatively you could clear with a STORE,SUB pair, at the cost of a >scratch location. You could have a microcoded bit that if set clears the AC. Depends on the number of bits you have to use. >>7 - READ > >After several partial designs than included IN and OUT operations, I >decided to punt I/O almost completely. In my current plans, one operation >can take the switch register as source, and the accumulator lights >(and/or other lights) are the only output. Limts the machine significantly. >>9 - CALL > >I have provisionally punted the CALL, too, as a separate operation; >instead, the same operation that can load the switch register into the >accumulator can similarly load the PC. Unfortunately my current design >requires the PC to then be adjusted explicitly in the subroutine. Look at how PDP-5/8 and other did it. Since memory was a universal store the first location of the JMS is the subroutine return address. That give a very simple implmentation but a real Jump to Suroutine. JMS SUB1 Breaks down to PC-> SUB1, SUB1->PC, PC+1->, fetch PC makes for simple state logic. >I'm still at the stage of designing and "building" fragments in a >simulator, since I have no real experience; I keep making things too >complicated, and then backtracking to simply again. (And I don't work on >it very often.) My current plan is roughly an 8-bit, >stripped-down-PDP8-ish architecture: Suggestion: Eliminate the ISZ from the PDP8 ops and make IOT and ISZ in to INPUT(to ac) and OUTPUT(from AC). Keep indirect addressing and drop page 0 addressing. AND TAD DCA JMP JMS OPR (skips, shifts, clears, misc ops) INP OUT three bit opcode, one bit for indirect address and 4bits for in page address. Direct addressing 256 bytes using indirect addressing. >Any bits in the instruction may of course end up complemented depending >on the nature of available gates :-) I want to hard-wire this one; if I >eventually finish it, next will come a 16-bit (or perhaps 12- or 18- or >24- bit) device with a more sophisticated instruction set and wide dumb >microcode in EEPROMs. Sounds like fun. >One is an 8-bit processor, built from TTL on an 8"x14" prototyping board, >with point-to-point soldered wire. The ALU is a pair of 74181s, and seems >to use 7475s for the registers. There are five sets of 8 LEDs -- memory >address register, program counter, instruction register, memory, and A good design to look at for simplicity and also to illustrate 8bit machine that could become the microcoded core of something bigger check out the controller used in the RX01. It had all the basic elements and was really simple. A variation of the disign was used in the LA120 printer. >A somewhat related 'thing' I picked up last week is some sort of logic >trainer. In a clear plastic frame about 12" x 20" x 6" thick, it has six >*huge* flip-flops (built with power transistors) each with a pair of >output lamps, a jumper area for "programming", and input in the form of a >telephone-style dial. (I assume people here know what a telephone dial is >:-) Haven't traced this one out yet either, but at its scale it won't be >hard. Aint seen one of those for years. Memory serves there were only a few FFs and verly little other logic. Allison

24 years, 2 months

RX02 drive emulation (was RE: Lisa Profile Drive emulation on a PC)

by ajp166＠bellatlantic.net

From: David Gesswein <djg(a)drs-esg.com> >I haven't spent too much time looking at the interface but most of the >smarts are in the drive and serial communication is used to send >commands to it. I have a bunch of information on the RX01, the RX02 should >be similar. Do look. the two are very different. >The cable I made to hook my 8 to the DB25 on the RX02 has 22 wires in it, I >don't remember how many are grounds. Every other one. same for RX01. Different signals though. Allison

24 years, 2 months

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test-drb November 2000