test-drb

test-drb@ccmp.vtda.org

101090 discussions

by Billy.Pettit＠wdc.com

I recently came across a stock of what seems to be 16 bit wide memory chips. But I'm getting nowhere trying to find a data sheet. Can anybody help out? The parts are UM61M512K-15, 32 pins DIP. The logo is round, world shaped with 3 vertical and 3 horizontal lines. Date codes are 95 and 96. The parts were on some mini-486 PCBs. If these really are 16 bit wide and 32K deep, they would be great for a SBC I'm building. Especially if the 15 means 15 ns. Any help for pinouts or data sheet greatly appreciated. Billy

18 years, 11 months

TTL homebrew CPUs

by dkelvey＠hotmail.com

>From: woodelf <bfranchuk at jetnet.ab.ca> > >dwight elvey wrote: >>Right now, we are at the power density limits for uP's. We can >>build smaller ones and put more circuits on a chip but we've >>hit the limits of power density. We get smaller improvements >>from lower K insulation on wiring but power is now the wall. >>Dwight > >Does this mean that if we reduce the number of transistors >we can go faster? Let see a PDP 8/Z(1) with current technology >would be? :) I think the problem is computer design rather >than the chip design -- You don't have random access memory >any more & salesmen push clock speed rather than a usefull >measure of computing power. > No, it means that you need to be more clever with the transistors that are there. The architectures of today's CPU's are doing several times as much per clock cycle than your PDP8 did. The problem is that they are also running out of tricks in a single CPU. That is why your seeing multi processors becoming more popular. I'm not sure where the future methods will go but they are still holding to Moore's law, just not with increased clock speed as the driving force any more. Dwight _________________________________________________________________ Don't get caught with egg on your face. Play Chicktionary!? http://club.live.com/chicktionary.aspx?icid=chick_hotmailtextlink2

18 years, 11 months

Intel uScope 820

by gksloane＠hotmail.com

Did you ever scan the manual for the Intel uScope 820? I have one, and I have the 8080 pod/probe/cable, and the 6K PRO module, but no documentation whatsoever. Whatever you have would be appreciated! If you have a scan of the manual and/or the service manual and can send it to me I'd be very very happy! Gary Sloane SB/US Engineering Inc. _________________________________________________________________ http://newlivehotmail.com

18 years, 11 months

Need Data Sheet

by ajp166＠bellatlantic.net

> >Subject: Re: Need Data Sheet > From: "Ethan Dicks" <ethan.dicks at gmail.com> > Date: Tue, 10 Jul 2007 15:08:19 -0500 > To: "General Discussion: On-Topic and Off-Topic Posts" <cctalk at classiccmp.org> > >On 7/9/07, Chuck Guzis <cclist at sydex.com> wrote: >> OTOH, there's a nice 16bit SRAM in some modems, such as the Hayes >> 28.8K external models. In an 0.300" wide DIP too. > >Oooh... that could be fun to play with. I didn't figure that a cache >SRAM was anything other than 4-bits wide (386/486 era) or 8-bits wide >(486/Pentium era), especially since I've used a bog standard cache RAM >on an 1802, but knowing there really are 16-bit-wide SRAMs could be >fun for, say, a 68000-based board, or even throwing away 4 bits and >using it as a 12-bit-wide single part for a PDP-8. > >Any idea what the part number might be for that RAM chip? Vendor? It's a 8bit wide part I have a bag of those and similar parts. FYI they are 15ns and for super fast memory systems as in cache but for fast systems they are the cats meow. > >-ethan

18 years, 11 months

TTL homebrew CPUs

by ajp166＠bellatlantic.net

> >Subject: Re: TTL homebrew CPUs > From: woodelf <bfranchuk at jetnet.ab.ca> > Date: Tue, 10 Jul 2007 11:04:27 -0600 > To: General Discussion: On-Topic and Off-Topic Posts <cctalk at classiccmp.org> > >dwight elvey wrote: >> Right now, we are at the power density limits for uP's. We can >> build smaller ones and put more circuits on a chip but we've >> hit the limits of power density. We get smaller improvements >> from lower K insulation on wiring but power is now the wall. >> Dwight > >Does this mean that if we reduce the number of transistors >we can go faster? Let see a PDP 8/Z(1) with current technology >would be? :) I think the problem is computer design rather >than the chip design -- You don't have random access memory >any more & salesmen push clock speed rather than a usefull >measure of computing power. > >(1) Zippy - 1000x faster the a PDP 8/E. >Now back to thinking about how to build a homebrew CPU... >Front panel or no Front panel. > The pdp8 limitation back then was not the CPU but the fact that it's timing was interlocked with the core. Take core out of the timing picture with fast Sram and crank it up then things like bus timing and ripple carry are a factor. So a turbo PDP-8 is achieveable and if it were all on a chip your "8/Z" would be scary fast with current tech. However if you reduce the number of transistors as MIPS and other RISC machines early on did your dependent on raw speed at the die level and the cycle repeats. That is you end up pushing for ever higher speeds to make up for simplicity and those transistors left are hitting the speed/power wall. Then of course you can try to push that by making the machine wider. The process does the lather, rinse and repeat with new process slipping in to help out but we are approaching the sub atomic level were transistors perform badly as there are not enough molecules in them! So we go back and add more parallel cpus on the same die and that means more transistors and we go around again. Allison

18 years, 11 months

Amstrad PCW 8256 and 3.5 DS2D Drives

by cclist＠sydex.com

I recently picked up an Amstrad 8256 for its floppy drive (Hint: replace the drive belt with a cheap polyurethane "elastiband" type of "rubber" band. It works great.) That left me with a machine that would either hit the recyclers or that I could keep around. When I looked at the basic box--4MHz Z80, graphics, 512K of RAM...I couldn't bear to toss it out without at least playing with it a bit. I installed a Teac FD235F 720K drive in place of the original one and then contemplated what I was going to do for a boot diskette. None came with the machine. Digging through my collection turned up a 3.5" CP/M 3.0 boot diskette for a PCW 9512 (DisKit), but simply trying to boot from it got me nowhere. (Beep Beep Beep). I found that the checksum of the boot sector identified the target boot machine. My sample checksummed to 0x01, where my documentation said that the PCW 8256 required a checksum of 0xff. Decrementing the "fixup byte" at offset 0x0f in the boot sector by 3 from 0xD1 to 0xCF did the trick. The lowly Joyce now boots CP/M. I've not seen this trick documented, so I thought I'd report it here. The easiest thing would have been to change the boot ROM code, but that appears to be buried in a gate array and not a regular EPROM. I note that the PCW uses the RST 7 vector for interrupts, which conflicts with the breakpoint interrupt used by DDT and ZSID. Fortunately, there appears to be a patch for that. While it might be fun to get the PCW to run MP/M II, my interest has waned a bit, so the thing will now go back onto the shelf. Without a regular printer or serial port, an anemic PSU and a horrible keyboard, it's going to be of limited utility anyway--for now. Cheers, Chuck

18 years, 11 months

Pics of my cleaned-up Crimson VGX.

by austin＠ozpass.co.uk

Thanks for all of the recent assistance regarding cleaning products for my Crimson VGX. A combination of Naptha (in Zippo lighter fluid form) and hot soapy water have cleaned it up a treat. In fact it?s now looking almost as good as new, pics here: http://ozpass.co.uk The system almost boots as well. I don?t have a keyboard for it so I?ve made a null-modem cable with USB adapter for my MacBook and hooked it to the VGX using minicom. This redirects the console to the serial port so I can watch it booting. Currently it?s halting whilst trying to mount an NFS share from a computer called ?Onyx?. I guess I?ll have to edit fstab to remove the offending entry. In other good news I?ve discovered an IRIX 5.3 CD in the drive, complete with caddy! It?s days like today with a sparkling clean functional SGI Crimson VGX in your kitchen that the hobby makes perfect sense (except to one?s better half! ;-) -Austin.

18 years, 11 months

TTL homebrew CPUs

by ajp166＠bellatlantic.net

> >Subject: Re: TTL homebrew CPUs > From: Dave McGuire <mcguire at neurotica.com> > Date: Mon, 09 Jul 2007 18:45:52 -0400 > To: "General Discussion: On-Topic Posts Only" <cctech at classiccmp.org> > >On Jul 9, 2007, at 5:51 PM, Tony Duell wrote: >>> recycled industry application notes), that required some special >>> circuit >>> only available at their or associated stores. Having seen the nth PIC >>> application that basically blinks a LED - what my generation built >>> with >>> 2 transistors, 2 capacitors, 4 resistors - is lame. >> >> You're making me feel very old. When I was a kid, I used to make a >> neon >> bulb blink using one resistor and one capacitor. > > Relaxation oscillators are fun. I like the UJT version as well, >though UJTs are getting harder to find than they once were. I have >two or three 2N2646 UJTs left. Yes but you can build your own UJT using a 2n3904 and 3906 plus two resistors. Allison > > -Dave > >-- >Dave McGuire >Port Charlotte, FL >

18 years, 11 months

Need Data Sheet

by ajp166＠bellatlantic.net

> >Subject: Need Data Sheet > From: "Billy Pettit" <Billy.Pettit at wdc.com> > Date: Mon, 09 Jul 2007 17:15:33 -0700 > To: <cctalk at classiccmp.org> > >I recently came across a stock of what seems to be 16 bit wide memory chips. >But I'm getting nowhere trying to find a data sheet. Can anybody help out? > > > >The parts are UM61M512K-15, 32 pins DIP. The logo is round, world shaped >with 3 vertical and 3 horizontal lines. Date codes are 95 and 96. > > Mine are 64kx8. Did you try google "um61512 datasheet"? Allison

18 years, 11 months

TTL homebrew CPUs

by ajp166＠bellatlantic.net

> >Subject: Re: TTL homebrew CPUs > From: woodelf <bfranchuk at jetnet.ab.ca> > Date: Mon, 09 Jul 2007 23:23:00 -0600 > To: General Discussion: On-Topic and Off-Topic Posts <cctalk at classiccmp.org> > >dwight elvey wrote: > >> If you really want them to act like a TD, place a resistor in parallel >> to give the final slope. It doesn't make them any better at doing >> fun things but is closer the a real TD. >> Dwight >But with a ka-zillion tunnel diodes you can build the fastest >computer ever. Well that was what all the hype was about in the >early 60's. >Did anyone ever use Junction Fets in computer logic? Not that I've seen. Likely reason for that is by time the JFETs became common enough production computers were IC based. However MOSfets on silicon did make it into IC as CMOS and well.. there in computers big time, Allison

18 years, 11 months

TTL homebrew CPUs

by Billy.Pettit＠wdc.com

Tony Duell wrote: I do? That's news to me. I am not sure there _was_ Elektor in the UK in 1974... The early UK computer projects I know about are : the 'PE Champ' (that's tue UK magazine 'Practical Electronics') from 1977 (a 4040-based computer + 1702 programmer + UV eraser) ; the PE Digi-Cal from 1972 (a 4-function dsektop calculator built in TTL + a diode-matrix ROM. I don't recall any general-purpose computer built from TTL in a UK magazine. [ snip ] -tony I believe that Elektor was publishing in the UK in 1974, but I don't have my copies at hand to pick the exact date. I know the first and second binders were full by the end of 1976 (I used to buy the publisher's binders, an icky green, tacky board binder). And I read all of them but do not remember any computer projects. And I would have been extremely interested because I was building an 8 bit TTL machine at the time. However, there was the ACS (Amateur Computer Society), an early UK computer group that designed and built a 16 bit TTL computer. It was well documented in their Newsletter in the mid-70's. All my copies were stolen, and I've looked for 20 years to find copies. Any chance of the UK CC'ers having copies of these newsletters? Billy

18 years, 11 months

S-100

by RodSmallwood＠mail.ediconsulting.co.uk

Thanks.. I did ... Rod -----Original Message----- From: cctech-bounces at classiccmp.org [mailto:cctech-bounces at classiccmp.org] On Behalf Of Andrew Lynch Sent: 09 July 2007 22:00 To: cctech at classiccmp.org; RodSmallwood at obmr.btconnect.com Subject: Re: S-100 Hi Does anybody have: a) A Northstar Horizon S100 Mother board (Need not be working or populated) b) The PCB artwork for the above. c) Any other S-100 mother board. d) The PCB artwork for the above. Anything more would be a bit expensive on shipping from the US. So its just the board that's required Rod Smallwood Hi Rod, Check out http://groups.yahoo.com/group/Verns_Stuff/ Vern has a NorthStar Horizon chassis with motherboard for sale. I'd bet he would sell you the motherboard alone if you made an offer. Tell Vern I sent you and you saw this on CCTALK mailing list. Thanks! Andrew Lynch

18 years, 11 months

S-100

by lynchaj＠yahoo.com

Hi Does anybody have: a) A Northstar Horizon S100 Mother board (Need not be working or populated) b) The PCB artwork for the above. c) Any other S-100 mother board. d) The PCB artwork for the above. Anything more would be a bit expensive on shipping >from the US. So its just the board that's required Rod Smallwood Hi Rod, Check out http://groups.yahoo.com/group/Verns_Stuff/ Vern has a NorthStar Horizon chassis with motherboard for sale. I'd bet he would sell you the motherboard alone if you made an offer. Tell Vern I sent you and you saw this on CCTALK mailing list. Thanks! Andrew Lynch

18 years, 11 months

Antique computer books for sale

by janprunk＠gmail.com

Hello ! I received some antique books about computing from the library. They are all in English language and in good condition. The price for one book is 3 Euros + postage. The books are shipped >from Slovenia, Europe. The link to the list is available at: http://yang.mtveurope.org/books.html If you are interested, contact me to my private email address. Kind regards, Jan Prunk -- +------------------------------------------------------------------+ | Jan Prunk GPG key: 00E80E86 | | E-mail: jan at prunk.be Fingerprint: 77C5 156E 29A4 EB6C 1C4A | | http://blog.prunk.be 5EBA 414A 29F5 00E8 0E86 | +------------------------------------------------------------------+

18 years, 11 months

Trace Wrinkles

by marvin＠west.net

> From: "Mike Hatch" <mike at brickfieldspark.org> > > I haven't heard anyone discuss this yet: what causes traces on some old > > PCBs to wrinkle and not others? My guess is a combination of suboptimal > > glue and wide temperature swings. > > > Caused by the hot air solder levelling process when a manufacturer skips a > process or has the process order slightly out. > The solder should only be deposited on the component pads, but some > manufacturers used to put the solder on before the silk screen, then level > the board. The solder melts during levelling and aggregates under the mask > forming the "wrinkles". > > It should be - silk screen, apply tin/lead to pads, level. > It can be - tin/lead, silk screen, mask, level. > but if its - apply tin/lead, silk screen, level - you get wrinkles. You seem to be implying that the wrinkles are a result of the PCB manufacturing process, and that is wrong; the wrinkles you are talking about occur during wave soldering at the assembly portion of the process. By going to SMOBC (Solder Mask Over Bare Copper), both the wrinkles and extra weight of solder picked up during the wave soldering process were eliminated. And of course, it was not a problem when the boards were hand soldered. The wrinkles are NOT caused by hot air leveling (that was my area of expertise when I was working as a field engineer installing/training/maintaining Gyrex Hot Air Levelers.) I know of no process or reason for putting soldermask over tin/lead and using Hot Air Leveling for the reflow process. Hot air leveling was mainly used for SMOBC boards. Solder gives a longer shelf life than the SealBrite coatings that were also fairly common a number of years ago, and thus Hot Air Leveling was also used on some boards without soldermask. The usual manufacturing process before hot air leveling was drill, electroless copper/copper plate, plating resist applied (either photographically or silkscreening), copper plate to desired thickness, tin/lead plate, strip resist, and etch. If the board was going to be hot air leveled, the tin/lead plating was chemically removed. Otherwise it went through a reflow process to alloy the tin/lead into solder before the soldermask was applied.

18 years, 11 months

Strange SCSI devices (was: Re: LISA)

by Arno_1983＠gmx.de

Ray Arachelian <ray at arachelian.com> wrote: > As as aside, there were lots of very strange things on SCSI busses back > in the day. Scanners were quite common, but there actually existed > printers, and even video cards on SCSI busses. :-) The SCSI video card > and ethernet card were useful for compact Macs that had a scsi port, but > no expansion slots. Not even to speak of some of the stuff the scientific camp came to use. I got two "Gradient DeskLAB" SCSI DSP boxen for audio I/O from a chair at University where they were used for speech recognition and synthesis in the context of an automatic phone-in train timetable information system. Unfortunately absolutely no documentation and/or software to go with them, not much about them in the web (except for some people stating they used them for diploma thesis and similar), so I'm looking for any information about them you could come up with. -- Arno Kletzander Studentische Hilfskraft Informatik Sammlung Erlangen www.iser.uni-erlangen.de Ist Ihr Browser Vista-kompatibel? Jetzt die neuesten Browser-Versionen downloaden: http://www.gmx.net/de/go/browser

18 years, 11 months

M9312 boot rom trade

by wacarder＠earthlink.net

I spent a little time yesterday going through my M9312 boot roms. I have a few spares for devices that I do not have, and I am looking for a few boot roms for devices that I do have. If anyone wants to trade or if you have the boot roms I need, contact me offlist at wacarder at usit.net. Spare ROMs that I have: 755A9 - RP02/03/04/05/06 RM02/03 757A9 - TU16 TE16 TM02/03 I am looking for these: 753A9 - RX01 811A9 - RX02 756A9 - RK05 760A9 - PC05 761A9 - TU60 758A9 - TU10 One other note: I found a few 'oddball' boot ROMs. By examining the contents of the ROMs, I determined that the mnemonics for them are DA and DN. Does anyone know what devices these are for? They are not listed in the M9312 technical reference. Thanks, Ashley Carder http://www.woffordwitch.com

18 years, 11 months

[lisaem] LisaEm 1.0.0 Released

by ray＠arachelian.com

LisaEm 1.0.0 has been released. Download is available at http://lisaem.sunder.net/downloads.html as usual. ------------------------------------------------------------------------------ Lisa Emulator Change History http://lisaem.sunder.net/ ------------------------------------------------------------------------------ 2007.07.06 - Display color balancing to remove fuzziness. 2007.07.05 - LisaConfig bugs found - overwriting date information with garbage on save of preferences. - corrected a bug preventing the grabbing of the host time and date. Found that MacWorks locks up when date is invalid. 2007.07.04 - LisaEm documentation completion 2007.07.03 - Testing various opcodes to locate scroll bar arrow bug in LOS not found, but eliminated shift/rotate opcodes. 2007.07.01 - regression testing to locate MacWorks bug - not found yet, high probability that it lives somewhere inside the C++ code. 2007.06.30 - added Mac OS trap symbol printing for A-Line traps for tracelog 2007.06.29 - fixed inability to detect no-floppy from Lisa boot ROM - fixed entry to Service mode - not perfect, need to attempt to boot from bad profile. - fixed tracelog bugs (hardcoded /log/lisaem-output)

18 years, 11 months

Altair Kits

by gstreet＠indy.net

Hello All, Regarding the Altair 8800 repro kit: An unsolicited plug -- This kit is of the highest quality. Because of my ridiculous commute schedules, I can only work on my kit sporatically. I missed my big chance to build one in 1975, and I when I saw this kit, I vowed not to miss it again. It's been a long time coming, but it was worth the wait. I love this kit!!! Kudos to Grant! Regards, Robert Greenstreet

18 years, 11 months

Old Modems and Telephony switches

by Peter.Coghlan＠EUROKOM.IE

> >I've got a lead on some four-wire and X.25 ("frame relay"?) stuff from University and just yesterday I got my second ADSL modem. What would it take to set up or "simulate" their counterpart (DSLAM?) at home? > Hi Arno, I've got some X.25 equipment which needs a good home. I have two Satelcom switches, two Dec DEMSB routers and two 4-wire NTUs ("baseband modems?") plus a few cables and manuals. The switches power up and can be configured from a console terminal but have problems retaining their configuration over a power off. This is probably due to a problem with the internal PCB mounted batteries which I have had to replace previously. One of them has a push-on connector from the power supply replaced by a soldered connection where the connector had overheated. The NTUs also power up and appear to work. I haven't tried the DEMSBs. Normally the NTUs are clocked from the telephone exchange end but it is possible to change the links in one to get it to generate a clock internally so that the two can talk to each other over a 4 wire crossover cable. At least, I can get all the LEDS to illuminate. I don't know enough about X.25 etc to get any further than that. Let me know if you are interested. However, I am located in Dublin, Ireland so I am not sure how it would be possible to get the stuff to you if you do want it. Regards, Peter Coghlan.

18 years, 11 months

cctalk Digest, Vol 47, Issue 12, Message 3 - Trace wrinkles

by mike＠brickfieldspark.org

> Message: 3 > Date: Fri, 6 Jul 2007 11:39:56 -0700 (PDT) > From: David Griffith <dgriffi at cs.csubak.edu> > Subject: trace wrinkles > > I haven't heard anyone discuss this yet: what causes traces on some old > PCBs to wrinkle and not others? My guess is a combination of suboptimal > glue and wide temperature swings. > Caused by the hot air solder levelling process when a manufacturer skips a process or has the process order slightly out. The solder should only be deposited on the component pads, but some manufacturers used to put the solder on before the silk screen, then level the board. The solder melts during levelling and aggregates under the mask forming the "wrinkles". It should be - silk screen, apply tin/lead to pads, level. It can be - tin/lead, silk screen, mask, level. but if its - apply tin/lead, silk screen, level - you get wrinkles. Wrinkles became less prevalent as tin/lead material costs went up, does not happen now as tin/lead here (UK) is banned except for special applications.

18 years, 11 months

trace wrinkles

by n8uhn＠yahoo.com

Hi All, i find it interesting that no one has mentioned the peel and press method of pcb making. some boards are not etched and placed in a chemical bath. instead the board starts as a copperless plate and the traces are on a sheet that carries the traces like a rub on transfer. the sheet has a protective layer that is removed and then the sheet is lay'ed on the blank pcb and pressed or rolled or vacuum pressure is applied. then the holes are drilled. after years of exposure to heat and air or even a bad transfer to start with, the traces "bubble" and wrinkle. i have not seen too many computer boards or cards made this way but alot of consumer audio and cb or marine two way radio's are made with this style of pcb and are a real pain to repair. when the trace is heated to replace a bad component, it wants to lift very quickly. my guess is that the peel and press way is cheaper then a real etched board. Bill ____________________________________________________________________________________Ready for the edge of your seat? Check out tonight's top picks on Yahoo! TV. http://tv.yahoo.com/

18 years, 11 months

TTL homebrew CPUs

by ed＠ed-thelen.org

Wakkkyness is not dead. "The Madscientist Builds a Processor" http://madscientistroom.org/table/mippy/ is the tale of a *second* electronics project, the first was a one chip TTL counter. Randy thought that was not hard, why not try a computer? He learned: - add lotsa capacitors between +5v and gnd, all over - ground can jump up and bite ya (a ground plane is a good thing) - and a lot of other practical stuff but crashed on, and finally succeeded :-))) Ed "Pops" Thelen

18 years, 11 months

TTL homebrew CPUs

by ajp166＠bellatlantic.net

> >Subject: Re: TTL homebrew CPUs > From: woodelf <bfranchuk at jetnet.ab.ca> > Date: Sun, 08 Jul 2007 16:06:02 -0600 > To: General Discussion: On-Topic and Off-Topic Posts <cctalk at classiccmp.org> > >Allison wrote: > >> If I were to do a TTL design right now I'd use 32Kx8 >> (or larger) parts even if the word size were 9 or 11 bits >> as they are cheap and easy to use and the unused excess bits >> are no real loss. >11 Bits ??? What uses that? Nothing I know of but theres no reason in the world to say that could not be done. >> Maybe because every time I did TTL or slice design I wasn't >> trying to make a period machine or be faithful I was doing >> some sacrelige but I was having fun and the expereince was >> no less because the memory, logic used or terminal was >> way out of period. > >If this your hobby , the main thing is to have fun. Roger that! ;) > >> Heck the guy that did the Apollo AGC has a hats off to me as >> he did in TTL something conceived as RTL with minimal data. >> If anything not only was a working machine a significant >> accomplishment but the information about it he dug up, made >> visible to public and preserved along the way speaks to >> great work. > >That was great work. I admire just finding all the data. That was a easter egg hunt if there ever was one. >> >> For those that try and or succeed to build a PISC >> (Pitiful Instruction Set Computer) or a VSC (Very >> Simple Computer) they are contributing a lot to the >> science and history of computing. After all there >> are many old (really old) machine preserved and sitting >> that most of us have not the first idea how to power >> up and program. Those that do it get my attention for >> their efforts. > >The Kenback 1 and the 6800 replica's that come >up is great work too. I wish I could get him >to do my cpu from my hen scratched schematics. >Now the biggest problem I have is do I want >Single Instruction or not with my minimal front >panel? Is that used that often that it needed? >Ben alias woolelf I have only done one front pannel, it was as much or more work than the CPU. It's all the wires and as I like to call it "drillin and blastin". So generally I try to avoid that or do a very minimal one for debug rather than show. The choice of what to build is always tough as there are so many choices. In the end I started with very simple state machines and microprogrammed controllers and gradually decided what capability was missing and how best to achieve it based on what I knew and had done. Whats funny is it's easier to design a slower wide word (32 or more bits) machine (lots of the same stuff repeated) than faster narrow word (8bit) machine. Then you get into variable word length or fixed, single address or multiple, register or memory based, microcode or random logic control, CISC or RISC. In the end whatever is built you're not going to be condemmed as at least it was built. >PS. How are IRQ's handeled when single stepping? Slowly. ;) Single stepping would just mean if there was an INT pending you would see all the steps and the adress changes involved. Or as I was told once, "Your the engineer, what do you want it to do?". Allison > > >

18 years, 11 months

S-100

by RodSmallwood＠mail.ediconsulting.co.uk

18 years, 11 months

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test-drb