test-drb

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101090 discussions

youtube movie of making a vacuum triode.

by dkelvey＠hotmail.com

> From: rtellason at verizon.net > > On Wednesday 16 January 2008 08:21, Gordon JC Pearce wrote: >> On Friday 11 January 2008 15:36:05 dwight elvey wrote: >>> Although, a side subject, I like Jay, consider tube manufacture >>> relavent to some of my computing equipment. >>> Dwight >> >> I wonder how much computing equipment you could make from home-made >> triodes? >> >> Even a simple (say 4-bit) adder would be pretty impressive. > > In power as well. > > It'd be darn-near EMP-proof, though. :-) > Hi I thought I might clarify what equipment I had. First it is not digital, it is an analog computer. Each tube calculates to about two decimal digits making each tube worth about 20 or so TTL equivalent. Dwight _________________________________________________________________ Climb to the top of the charts!? Play the word scramble challenge with star power. http://club.live.com/star_shuffle.aspx?icid=starshuffle_wlmailtextlink_jan

18 years, 3 months

HP/CHM software release update?

by Tim＠Rikers.org

I email Al, but did not yet get a reply. I realize folks are busy, so I thought I'd ask on the list for an update. Anyone know the status on releasing the older Hewlett Packard software that the agreement with the Computer History Museum allowed for? I know there are others on this list that have HP software, is it now legal to put that up someplace? or does it need a CHM stamp of some kind first? Is the agreement available for review? Side Note: I'll be in San Jose tomorrow (Jan 23) and plan to drop by the CHM in the afternoon. I'll hit some stores and scrounge sites in the area as well to see what I can find that I can't possibly take back on the plane with me. :) You suppose I could check an HP-2116 as luggage? 230lbs might be a bit over the weight limit, but it's close, right? :) -- Tim Riker - http://Rikers.org/ - TimR at Debian.org Embedded Linux Technologist - http://eLinux.org/ BZFlag maintainer - http://BZFlag.org/ - for fun!

18 years, 3 months

Head alignment for legacy Sony FDD

by pludikar＠sympatico.ca

>Most heads have two sets of windings. One for trim erase and a second >for read/write. The organization varies but the trim is two pins or >have one pin in common with R/W and the RW is often a centertapped >winding (three wires) so you should see three connections of near >zero ohms and a pair that are also near zero OR 4 pins that show >near zero (common wire case). > >The test for alignment usually requires a calibration disk and scope >but I've done it by doing reads of a known good disk and "finding >the edges" and setting it for the middle. Track 00 is usually less >critical so if it happens when the head out and you can boot or read >the disk thats usually good enough. > >Allison Allison - thank you very much. I've measured the replacement heads and it looks like they may be damaged. There are 5 connections to each head - on the upper head, 3 connections measure zero, and on the bottom head, 4 connections measure zero. The bottom head is consistent with another head (damaged) I have. I know that the replacement heads were able to read data, but caused the tracks to erase when writing, so I still would expect to be able to use them. The major question I have, though, is how do you change the position of the head to calibrate it? On the MPF-52W-30 (sorry I inadvertently gave wrong number last time) there's a variable pot RV101 and 2 pins to IC101 (CXD1007B) associated with X-adj and X-reset. Other than setting the position of Track 00, these look like the only options available to move the heads a fraction of a step. I'd be grateful for any thoughts or suggestions. Peter

18 years, 3 months

Free Sun Enterprise 450 server and A-1000 RAID, London UK

by lproven＠gmail.com

Anybody want a free Sun? I know the chap offering this personally, as it happens... - LP ---------- Forwarded message ---------- From: Roger Burton West <roger+freecycle at firedrake.org> Date: 22 Jan 2008 14:03 Subject: [FreeCycleLondon] OFFERED Sun Enterprise 450 server and A-1000 RAID, E13 To: FreecycleLondon at yahoogroups.com This is not capable of being used as a normal PC. It's a _large_ Sun server dating from around 1999 (model introduced in 1997). Four 400MHz UltraSparc-II processors, 4GB RAM, no discs on board but the A-1000 RAID unit has about 100GB in it. No monitor or keyboard. Solaris 8 installed, but a licence to run it is up to you (or just throw on Linux or a more recent Solaris). This is a big and heavy machine - 58cm high, 45cm wide, 65cm deep. It'll fit in an estate car or a van, but I wouldn't want to try it in a normal saloon. Loading or unloading is a job for at least two energetic people; I'll help you at this end. This is a very nice piece of kit, but I just don't have room for it and I'd like it out of my life as soon as possible... Roger -- Liam Proven ? Profile: http://www.linkedin.com/in/liamproven Email: lproven at cix.co.uk ? GMail/GoogleTalk/Orkut: lproven at gmail.com Tel: +44 20-8685-0498 ? Cell: +44 7939-087884 ? Fax: + 44 870-9151419 AOL/AIM/iChat: liamproven at aol.com ? MSN/Messenger: lproven at hotmail.com Yahoo: liamproven at yahoo.co.uk ? Skype: liamproven ? ICQ: 73187508

18 years, 3 months

random unloved things

by dgriffi＠cs.csubak.edu

I have some stuff that's free for shipping: Three 10base-FL AUI-to-fiber transceivers One ISA SCSI card with DB25 connector. It's a PEL 1600 and carries an Adaptec AIX-63600 chip. -- David Griffith dgriffi at cs.csubak.edu

18 years, 3 months

DEC/VG Datasystem/System Industries/Western Dynex

by jaspat＠netmagic.net

Jay, I was trying to locate the name of the owner/founder of Western Digital and came across your note re System Industries disk controller and Western Dynex drive. I was the VP of Engineering at System Industries >from 1973 to 1979. The 3040 and 3051 were disk controllers we developed during that time. As I recall the 3051 was a 3040 with ECC added - could be wrong. I am still in touch with some of the engineers from those days who may be able to answer specific question. Let me know. Jim Patterson mail4jlpatterson at yahoo.com

18 years, 3 months

Head alignment for legacy Sony FDD

by dm561＠torfree.net

-----------Original Message: Date: Mon, 21 Jan 2008 20:47:21 -0500 From: "Peter" <pludikar at sympatico.ca> Subject: RE: Head alignment for legacy Sony FDD > 4 shorted together ('measuer 0') and one unconencted one would be what I > expect. > The uncconected one will be at one end of the head edge connector > fingers. On the damaged head, which _other_ one is unconnected ? On the damaged head, three fingers at one end show shorted. I guess that means: 3) Other end of the R/W coil, 4) Centre tap of R/W and 5) Erase Are probably okay. Finger 2) shows o/c - this would be consistent with the fact that before I managed to fry the drive, the FDD could read data but on writing I lost all data (ie everything was erased) >> there's a variable pot RV101 and 2 pins to IC101 >> (CXD1007B) associated with X-adj and X-reset > Are these related to head alignment? I must say I am rather suprised. > Normally you physically move the head stepper motor slightly. There doesn't appear to be a physical way of moving the heads - I was speculating/hoping that RV101 and the 2 X related pins may have something to do with fine adjustment - but I have no real idea. The heads are mounted on a diecast bracket with locating holes. There are corresponding centring pins on the main diecast body and there's no discernable movement when the two are mated. I rigged up a small Shugart type interface board with manual switches that allowed me to exercise the main drive control (drive select, motor on, step direction, step etc.). The control logic on the FDD stops the head from stepping in the down direction once the track 0 sensor is activated. So my one of my thoughts is that the track 0 sensor actually defines the fine head position, but I don't know for sure. Any thoughts or suggestions? -Peter -----------Reply: The track 0 sensor defines the track numbers, i.e. which track to start at. Adjusting where those tracks actually are on the disk is usually done by rotating the stepper motor; AFAIK there's no way to do that with any non- mechanical adjustment. I'd leave that as a last resort though; within reason, neither should affect the drive's ability to write to a *blank* disk and read those disks, and alignment and track 0 are probably not your issue. m

18 years, 3 months

altair turnkey with internal drives

by evan＠snarc.net

Just remembered -- Pertec. -----Original Message----- From: "Evan" <evan at snarc.net> Subj: Re: altair turnkey with internal drives Date: Tue Jan 22, 2008 1:37 am Size: 716 bytes To: "General Discussion: On-Topic and Off-Topic Posts"<cctalk at classiccmp.org> Maybe some form of the Attache? I forget who made it ... might've been a company with a 'P' in the name that bought MITS? (I'm not at a computer to look it up right now.) -----Original Message----- From: David Griffith <dgriffi at cs.csubak.edu> Subj: altair turnkey with internal drives Date: Tue Jan 22, 2008 12:59 am Size: 345 bytes To: cctalk at classiccmp.org Has anyone here heard of an Altair 8800 turnkey with internal floppy drives? I found one in the estate in Pasadena I'm liquidating. -- David Griffith dgriffi at cs.csubak.edu A: Because it fouls the order in which people normally read text. Q: Why is top-posting such a bad thing? A: Top-posting. Q: What is the most annoying thing in e-mail?

18 years, 3 months

altair turnkey with internal drives

by evan＠snarc.net

Maybe some form of the Attache? I forget who made it ... might've been a company with a 'P' in the name that bought MITS? (I'm not at a computer to look it up right now.) -----Original Message----- From: David Griffith <dgriffi at cs.csubak.edu> Subj: altair turnkey with internal drives Date: Tue Jan 22, 2008 12:59 am Size: 345 bytes To: cctalk at classiccmp.org Has anyone here heard of an Altair 8800 turnkey with internal floppy drives? I found one in the estate in Pasadena I'm liquidating. -- David Griffith dgriffi at cs.csubak.edu A: Because it fouls the order in which people normally read text. Q: Why is top-posting such a bad thing? A: Top-posting. Q: What is the most annoying thing in e-mail?

18 years, 3 months

altair turnkey with internal drives

by dgriffi＠cs.csubak.edu

Has anyone here heard of an Altair 8800 turnkey with internal floppy drives? I found one in the estate in Pasadena I'm liquidating. -- David Griffith dgriffi at cs.csubak.edu A: Because it fouls the order in which people normally read text. Q: Why is top-posting such a bad thing? A: Top-posting. Q: What is the most annoying thing in e-mail?

18 years, 3 months

Lot of 176 PDP-11/DEC Boards

by root＠parse.com

Hello, I'm wondering if anyone here is interested in purchasing the following lot of boards (I count 176) -- the vast majority of these are PDP-11 cards. I'd rather get rid of them in one lot than eBay them individually and deal with the hassles. This inventory is to the best of my knowledge, I would of course physically verify inventory before we finalized anything. I am located in Kanata, Ontario, Canada, K2M 1C5 for shipping, and I can do Canada Post, UPS, or Fedex (Ground or Express). I am entertaining offers until the end of the month or so; please email me directly. Cheers, -RK 4 M105 Address Selector 2 M234 KE11-A Registers 1 M7071 Waveform Generator 3 M7104 RK05 Disk Controller 1 (data buffer retgister and status) 3 M7105 RK05 Disk Controller 2 (major registers) 3 M7106 RK05 Disk Controller 3 (control module) 1 M7227 Plotter Control 2 M7228 REAL TIME PROGRAMMABLE CLOCK 1 M7263 UNIBUS CPU Module 2 M7264 LSI 11 CPU 1 M7265 KD11E PDP-11/34 Data Path 1 M7266 KD11E PDP-11/34 Control 1 M7270 KD11 1 M7516 DELQA Ethernet Adaptor 1 M7700 Dec Pak Index and Sector 5 M7705 Drive Control Logic 5 M7706 Interface Timing 6 M7707 Servo Control 6 M7708 Track Position Detector / PLO 1 M7710 Print Sequencer 1 M7711 Control Logic A 1 M7712 Control Logic ? (Blotted out, guess "B") 1 M7713 LCV 1 M7714 ? 1 M7715 Line Feed Control 1 M7716 HS50 Motor Translator 2 M7717 Motor Control 1 M7726 Floppy Disk Controller 1 M7727 Read/Write Control 5 M7729 RK06 SERVO ANALOG 1 M7744 RX-02 Floppy Disk Controller 1 M7745 RX-02 R/W Control 1 M780 KL11 U Teletype transmitter & receiver for KL11, 110 baud 2 M7800YA ASYNC TRANSMITTER & RCVR, WITHOUT EIA CHIPS,CURRE 1 M781 PC-11 Control 2 M7810 PC-11 Interface 2 M782 Interrupt Control 4 M7821 Interrupt Control 2 M783 Unibus Drivers 2 M784 Unibus Receivers 1 M7843 DR-11 2 M7846 RX11 Unibus Interface 7 M7847 MS11 (One of these is missing the voltage regulator (TO-3 package)) 4 M7850 Parity Module (2) 8 M7856 DL11-W,SLU/RTC OPTION 2 M7859 KY11-LB Programmer's Console 7 M7860 DR11-C = M786 + M105 + M7821 3 M7867 DVP 11-DA 1 M7895YA 48 (5V Optical Isolated) Channel Input DSS11 3 M7940 Serial Line Unit 4 M7941 16-bit Parallel Line Unit (DRV11) 8 M7944 4K RAM 3 M7946 RXV11 LSI 11 Interface 1 M7949 LAV-11 1 M7950 DRV11-B 1 M7952 Programmable Realtime Clock 1 M7955 MSV11-C LSI MOS Memory (4x16xIntel2104) 1 M796 Unibus Master Control 1 M798 UNIBUS driver 1 M7992 TXM UNIBUS CONTROL & CRC 1 M8012 Boot-Terminator and Diagnostic ROM Module 1 M8013 RLV-11 Disk Control 1 M8014 RLV-11 Bus Control 1 M8029 RXV21,Q-BUS RX02 INTERFACE,DO 2 M8043 DLV11J 4 Serial Line Unit 2 M8044DB 32k x 16 MOS Memory (M8045 PCB) 1 M8044DF 32k x 16 MOS Memory (M8045 PCB) 2 M8047 MXV 11 A 2 M8186 KDF11-AC DUAL HEIGHT CPU,Q-BU 3 M8192 DUAL HEIGHT CPU BRD (KDJ11-A) 1 M8256 RX211, UNIBUS RX02 INTERFACE 1 M8264 NO SACK Timeout Module 1 M8265 KD11E-A PDP-11/34A Data Path 1 M8266 KD11E-A PDP-11/34A Control 1 M827 KE11-A Clock & States 1 M8403 4 SLU 1 M8916 Logic and Write Board 1 M8931 Slave Clock and Motion Delay 1 M9001YC Gen Purpose Card 4 M9016 RK06 Cabling Bd. 1 M9301YA Bootstrap 2 M9301YF PDP11 Unibus Terminator/Bootstrap 1 M9302 11/04 UNIBUS TERMINATOR,FAR E -- Robert Krten, PARSE Software Devices, http://www.parse.com/resume.html

18 years, 3 months

Looking for a PC 5150 Keyboard

by richard.beaudry＠gmail.com

Hello all, I have an IBM 5150 PC in need of a new keyboard .... Willing to pay some $$, but hopefully not too much! :-) If anyone has one, can you please let me know how much you want for it? Also, please quote shipping to 01473. Thanks! Rich B.

18 years, 3 months

DEC Flip-Chip transistor cross?

by bnansel＠bigpond.net.au

I've Googled till I'm blue, but I haven't been able to find it. What would be a good cross for a DEC 3639 PNP transistor? Or, failing that, what are the specs for this transistor? -Bobby

18 years, 3 months

Head alignment for legacy Sony FDD

by pludikar＠sympatico.ca

Hi, I've been trying to create a working Sony MPF50W (as found in the HP1650B logic analyser) from 2 damaged units. One unit had a fried board and the other unit had physically damaged heads. I moved the heads and track 0 sensor from the fried board to the other board and I need to do 2 things: a) confirm that the "new" heads are actually working and b) realign the track 0 sensor. I'm reasonably sure that the heads are okay, they show continuity on some of the pins, but I'm not 100% certain that is what I should be expecting. I can't find any obvious sources of information on where to probe to see useful signals from the heads or find any procedure to align the sensor. I have Tony Duel's diagrams of the HP9114 from hpmuseum.net . Any suggestions on where to find this information or how go about this would be really appreciated. Many thanks Peter

18 years, 3 months

Teletype 43 manual

by erzzf＠tiscalinet.it

Hi, I am looking for the teletype model 43 user manual and cable pinouts. Would you be so kind to help me? Thanks, Ernest

18 years, 3 months

Backing up TK50s (was: VMS 6.2 or older install media needed.)

by dave06a＠dunfield.com

> I'm not sure about the legal situation, but I think it would be worth > making a copy on some other media before the TK50s become unreadable. > > Regards > > Rob A timely discussion... Last week I received a total 4 TK50 drives, and a box containing 15 TK50 cartridge tapes. Of the four drives, one is a 1/2 height SCSI drive that is contained in a "low flat" DEC box (like the Microvax 3100). The other three are full-height TK50s, one of which is installed in a "cubish" (like the MicroVAX-2000) DEC box with a SCSI controller. The box is labled "TK50Z". I do know that this last drive was used quite recently. Of the 15 tapes, 8 of them appear to be original distribution media, and are "factory labled": AQ-FP13C-BN 03-Mar-87 MICROVMS V4.4 FULL BIN TK50 (C) 1986 DIGITAL EQUIP. CORP. AQ-FY80B-BN 03-Mar-87 MICROVMS V4.4 BIN TK50 MANDATORY UPD (C) 1986 DIGITAL EQUIP. CORP. AQ-JG62A-BN 03-Mar-87 MICROVMS V4.5 BIN TK50 (C) 1986 DIGITAL EQUIP. CORP. AQ-FP59C-BN 31-Mar-87 VMS LIC KEY BIN TK50 (C) 1986 DIGITAL EQUIP CORP. AQ-FP86J-BN W0035602 VAX FORTRAN 5.2 BIN TK50 FORT052,DEBUGMP050 (C) 1989 DIGITAL EQUIP. CORP. AQ-FP86E-BN 18-Feb-87 VAX FORTRAN 4.6 BIN TK50 FORT046 FORT (C) 1987 DIGITAL EQUIP. CORP. WIN/TCP Release 3.1 For MicroVAX VMS Computers License # 9074-IP _______ SID # ____________________ VD9962003 REV E uVAX TS11 DRIVER (C)1986 EMULEX The remaining tapes are mostly unlabled, although there are a few with handwritten labels: PSCA_E07042 Pathworks V4.2 Patch VAX/VMS 5.4-1 S/A BACKUP VMS V4.6 Q's: 1) Are any these titles already backed up somewhere? Are they worth backing up? (I assume everything requires licenses - I don't have the machine the VMS LIC tape was issued for). 2) What is the best way to backup these tapes to a more permanent media? Can they be read into binary files, and if so, can anything be done with those files? Presumably, as long as the tape blocks were archived, one could write a SCSI tape emulator if one really had to - or does such a thing already exist?) I have available: - Vaxstation 4000 VLC running VMS 5.5 - Vaxserver 3100 running OpenVMS 7.2 - Vaxstation 3100 running NetBSD All have SCSI ports. I relatively green at VMS from a system administration viewpoint (used it as a user lots in years gone by). I've never mounted or used tapes, but with a bit of guidance I'm willing to try and recover these if anyone has interest in their content. 3) What is "MICROVMS" - Is this just VMS (for a uVAX)? Dave -- dave06a (at) Dave Dunfield dunfield (dot) Firmware development services & tools: www.dunfield.com com Collector of vintage computing equipment: http://www.classiccmp.org/dunfield/index.html

18 years, 3 months

Bells on terminals (was: Re: YouTube videos of ASR33, etc.)

by tsw-cc＠johana.com

The discussion of bells on terminals reminded me of a weird experience. I had built up a terminal using a Qume printing mechanism (Sprint 4 interface) and added a keyboard and UART to make it complete. The printer didn't have a "bell" so I had to make one. In looking around for a nice tone to use, I found the one from the baud rate generator (MC14411). Since I was using an ASCII sequence, I had little use for the 134.5 rate (it is used for IBM 2741's) so I picked it up and with the use of a (couple?) one-shot, I made it into the beep. It was 16x the rate, so the tone was 2153.3Hz (see the data sheet). It worked quite nicely, and was pleasant sounding enough. Both control-G's and I were happy. Then the terminal was hooked up to an acoustic modem. While this isn't bad in itself, the astute among us will note that the tone for the bell is very near the center of the passband (2025-2225Hz) of the originate modems detector. So, every time someone sent a control-G to the terminal ALL sorts of weird things happened. Needless to say, I changed the wire to a different tap on the MC14411 baud rate generator chip. Yes, hardware can have unexpected bugs. Somewhere I still have this terminal. Daisywheel printers were fun to play with. I have the schematics somewhere if anyone needs info. -- Sorry, No signature at the moment. ____________________________________________________________________________________ Be a better friend, newshound, and know-it-all with Yahoo! Mobile. Try it now. http://mobile.yahoo.com/;_ylt=Ahu06i62sR8HDtDypao8Wcj9tAcJ

18 years, 3 months

Backing up TK50s (was: VMS 6.2 or older install media needed.)

by aek＠bitsavers.org

Q's: 1) Are any these titles already backed up somewhere? -- many of them have been. The license PAKs are less common 2) What is the best way to backup these tapes to a more permanent media? -- I use Eric Smith's tape copy program http://www.brouhaha.com/~eric/software/tapeutils/ which generates .tap images on a Linux box using a TZ30. TZ30's are handy because the head is easily disassembled to clean; something you do a LOT reading TK50's from the mid-80's 3) What is "MICROVMS" - Is this just VMS (for a uVAX)? -- correct. somewhat stripped down version of same.

18 years, 3 months

PDP 11 rescue.

by silvercreekvalley＠yahoo.com

Thanks for the replies. I've sent emails off list. Ian. ____________________________________________________________________________________ Be a better friend, newshound, and know-it-all with Yahoo! Mobile. Try it now. http://mobile.yahoo.com/;_ylt=Ahu06i62sR8HDtDypao8Wcj9tAcJ

18 years, 3 months

NEC component description/datasheet

by bear＠typewritten.org

I'm trying to identify a couple of devices. Google is leaving me cold. Part numbers: NEC B975 (also has "L 96" marking) and NEC D1309 ("K 98", like the former). Both are TO-220 package. Can anyone help? Thanks! ok bear

18 years, 3 months

Reading Polymorphic double density double sided disk.

by cclist＠sydex.com

Date: Fri, 18 Jan 2008 18:20:45 -0800 From: dwight elvey <dkelvey at hotmail.com> > For this, I need a little help. Since the 8 inch drives were 32 sectored, > calculating tracks from a disk offset number was easy. 5.25 disk with 10 > sectored will require something different. Is there an easy way to to > separate track from sector using Z80 code? Dwight Do you mean "is there an easy way to divide by 10?". If so, yes: 0.100x = x/16+x/32+x/256+x/4096+x/8192 to about 0.04 percent (4 parts in 10,000). Truncate the series if you need less accuracy. Ask if you need Z80 code. Cheers, Chuck

18 years, 3 months

YouTube videos of vintage PDP-11/40, ASR-33, VT05, etc

by wacarder＠earthlink.net

>> I never knew that an ASR-33 had a bell like an old typewriter to >> indicate that your near the end of the line. Funny! The computers >> probably had a special microphone to hear it when printing a directory >> listing :-) > >I though the 'end of line' trigger for the bell was actually an option, >but that all Model 33s (RO, KSR, ASR) had the bell which was mechanically >triggered by a ^G character. >Oh yes, the VT50 series of DEC terminals have a little relay on the logic >board. It'spulsed to geenrate the keyclick and sent a square wave signal >to generate the 'bell' which sounds rather like a 'raspberry'. >-tony Maybe I need to make a video of the VT52 with the ^G bell sound. It is a strange sound. We used to write programs on the PDP-11 back in the 70s to "ring the bell" under certain conditions (winning a game, etc.). Note on my videos that the VT05 (DEC's early video terminal) also buzzes at the end of the line on long lines. Ashley

18 years, 3 months

DEC Flip-Chip transistor cross?

by djg＠pdp8.net

> I've Googled till I'm blue, but I haven't been able to find it. What > would be a good cross for a DEC 3639 PNP transistor? Or, failing > that, what are the specs for this transistor? > 2N3639. My cross here. It doesn't seem to be picked up by the search engines for some reason. http://www.pdp8online.com/pdp8docs/decsub.txt

18 years, 3 months

PDP-11 backplanes

by legalize＠xmission.com

Thanks everyone who contributed to the PDP-11 backplane discussion that was a side-thread on the PDP-11/70 board set discussion. I really had no idea that the backplane in a PDP-11 machine was essentially a board interconnect and not a "bus" in the typical sense. Now I understand what's geeky interesting about PDP-11s much more than I did before. Before that discussion, I was under the impression that they were all just typical shared address/data busses on those backplanes. My PDP-11/03 is Q-bus and its more like that than the PDP-11s that are not the VLSI versions. Thinking about it, it makes much more sense because the CPU is divided among a large number of boards and having them all sit on a common bus would be quite damaging to the performance of the CPU. So I'm guessing the way you figure out how these various CPUs are implemented using the boards is to look at the schematics and infer the connections on the backplane from those? -- "The Direct3D Graphics Pipeline" -- DirectX 9 draft available for download <http://www.xmission.com/~legalize/book/download/index.html> Legalize Adulthood! <http://blogs.xmission.com/legalize/>

18 years, 3 months

Supply voltage for 2N2/256-BSCP

by bnansel＠bigpond.net.au

OK, I'm building the bit-serial ALU for my 2N2/256 project. Though it sounds exceedingly elementary, one design variable I haven't been able to figure out is what supply voltage I should use. Does anybody know why the 7400-series TTL used +5V for Vcc? I've looked at the equivalent circuits for TTL and LSTTL. Maybe I'm missing something, but it's not immediately obvious to me why such circuits couldn't operate on, say, 4.5V or 6V. I understand the need for good regulation to maintain noise margin, but why in 1964 did Texas Instruments chose 5V in particular for TTL? Was it just an arbitrary choice, or is there a deeper issue? -Bobby

18 years, 3 months

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test-drb