Slashdot Mirror

How to build your own ZX80/ZX81.

Probably a bit less kit-like than you're after, but eminently doable. Burning the eprom is probably the 'hardest' part; the rest is just painstaking detail. I've been meaning to build one for a few years now but originally work, and now study, keep getting in the way.

Actually this reminds me of those Old machines that old astronomers used to try to explain how the heavens worked. Before we knew that we weren't the center of the universe... before the understanding of retrograde motion, they just kept adding gears to these things to make it work closer and closer to what they saw. They thought the answer to everything was "It must be more complex than what we understand". If I have learned anything in my life worth knowing is that the universe than we want to give it credit for.

I'm shocked it doesn't seem to be offered on the Epson 1400.

Shocked. And stunned. Very stunned.

http://skyjude.users.btopenworld.com/rutles.htm

I'm with Bill Hicks on this:

"By the way if anyone here is in advertising or marketing... kill yourself. No, no, no it's just a little thought. I'm just trying to plant seeds. Maybe one day, they'll take root - I don't know. You try, you do what you can. Kill yourself. Seriously though, if you are, do. Aaah, no really, there's no rationalisation for what you do and you are Satan's little helpers, Okay - kill yourself - seriously. You are the ruiner of all things good, seriously. No this is not a joke, you're going, "there's going to be a joke coming," there's no fucking joke coming. You are Satan's spawn filling the world with bile and garbage."

Don't mod this Funny - there's no joke coming. Really. http://sazmatazz.users.btopenworld.com/ for the moreness.

Shift-4 is $ in the UK. They also switch " and @ so to type a " you press shift-2 and to type a @ you press shift-' (which is weird)

What video memory? The ZX81 generates screen output something like this: an interrupt routine eating 75% CPU time feeds character data to hardware shift registers, that produce a line of black&white dots on the screen. Repeat (carefully timed) until screen is done, and then remaining 25% CPU time (vertical blank period) is left for doing useful work until new TV frame begins.

It also had "fast mode" that did away with this, leaving snow on the TV screen (but at a 4x gain in processing speed!). I always loved this machine for its wonderful use of the limited hardware. You can even build your own, or personally type in a flicker-free space invaders clone on it.

Still used for things like controlling model trains or stepper motors, or re-built by programming the entire machine's function into a FPGA. Note: color in screenshot on last link is surely not on original hardware...

What video memory? The ZX81 generates screen output something like this: an interrupt routine eating 75% CPU time feeds character data to hardware shift registers, that produce a line of black&white dots on the screen. Repeat (carefully timed) until screen is done, and then remaining 25% CPU time (vertical blank period) is left for doing useful work until new TV frame begins.

It also had "fast mode" that did away with this, leaving snow on the TV screen (but at a 4x gain in processing speed!). I always loved this machine for its wonderful use of the limited hardware. You can even build your own, or personally type in a flicker-free space invaders clone on it.

Still used for things like controlling model trains or stepper motors, or re-built by programming the entire machine's function into a FPGA. Note: color in screenshot on last link is surely not on original hardware...

>>right next to the $1.99 Wal-ynol is a $4.99 bottle of Tylenol. It's the same medicine, but somehow people are convinced the name brand is better.
This is supposed to endear us to these people?
I think Bill Hicks put is best:
"By the way if anyone here is in advertising or marketing... kill yourself."

http://lungfishstudio.users.btopenworld.com/mung/f lash/aksjeeves.swf

Brian Millar's excellent Executive summary of Hamlet in Powerpoint. It includes a handy SWOT analysis of the Danish royal family.

He's also got a PDF version.

Brian Millar's excellent Executive summary of Hamlet in Powerpoint. It includes a handy SWOT analysis of the Danish royal family.

He's also got a PDF version.

I cant remember where I first saw the stuff linked below, some of the ZX stuff wasnt quite closed source enough.
Prepare your soldering iron:)

How to build your own ZX80/ZX81
Another zx81 clone using an FPGA
Yet another ZX81

I was about to say "Shame no one's done it for a Spectrum", but a quick Google search reveals that someone has. I am not worthy.

Is this a worthy haggis?

Well, I can't claim to know an answer to this, but can tell you this. In a conversation with a guy who worked for one of Britain's biggest ISPS (BT Openworld since you asked), whose role related to network security and the like, I was told that 70% of the traffic across their network was porn.

Now, bear in mind that this is a network catering primarily for residential customers, so this figure would be balanced out by business use when you look at the wider picture for the Internet in general, but there you have it. Also, he didn't seem to be taking P2P into account with that figure - I think he was referring to Web traffic only.

Oh, great, now I googled for "Free market defense contractor" and have to get this reference to Ayn Randian policies at Boeing out of my head... shame on you, baiting me like that.

More importantly, in terms of realism regarding UK broadband connectivity:

ADSL-For-Ipswich | Barnt Green, Birmingham | Edenbridge, Kent | Brinscall, Lancashire | Chafford Hundred, Grays | Broxburn/Uphall, Scotland | New Mills, Stockport | Bradford-on-Avon | Antrim, Northern Ireland | Paddock Wood, Kent | Mossley, Greater Manchester | Maltby, Rotherham | Cudworth, South Yorkshire | Pembury, Kent | Telford, Shropshire | Totnes, Devon | Caister on Sea, Great Yarmouth | Broadband in the East of England | Wargrave, Berkshire | Alton, Hampshire #1 | Alton, Hampshire #2 | Frodsham, Cheshire | Atherstone, Warwickshire | Sleaford, Lincolnshire | Neston, South Wirral | Blackpool/Fleetwood, Lancashire | Colwyn Bay, Wales | Whitby, Yorkshire | Saltcoats/Ardossan/Stevenston, Strathclyde | Thornbury, South Gloucestershire | Dinnington, Sheffield | Irby, Wirral | Colwyn Bay/Old Colwyn/Rhos-On-Sea, North Wales | Hednesford, Staffs | Connahs Quay/Flint/Mold/Sealand/Queensferry, North Wales | Eastham/Wirrall, Cheshire | Worle, North Somerset | Dereham, Norfolk | Leicester Kirby Muxloe, Leicestershire | Bolton Westhoughton, Lancashire | Leek, Staffordshire | Ivybridge, Devon | Attleborough, Norfolk | Whaley Bridge, Derbyshire | Montrose, Angus, Scotland | Hurstpierpoint, West Sussex | Worcester/St Johns/Fernhill Heath, Worcester | Allerton, Liverpool (and surrounding exchanges) | Buntingford, North Hertfordshire | Glastonbury, Somerset | St Budeaux, Devon | Fenland towns of Ramsey, Yaxley, Whittlesey, Chatteris, Ely and Soham | Grimsby, North East Lincolnshire | Pershore, Worcs | Yarmouth, Norfolk | Great Oakley, Corby, Northants | South Woodham Ferrers, Essex | Goring & South Stoke, South Oxfordshire and Streatley & Lower Basildon, West Berkshire | Kinross & Milnathort, Perthshire | Bolsover, Derbyshire | Elton, Ince and Helsby in Cheshire | Hanwell/Horley/Wroxton/Balscote/North Newington/Drayton, Oxfordshire | Tonyrefail/Gilfach Goch and surrounding area, Mid Glamorgan | Rotherfield Greys/Rotherfield Peppard/Shepherds Green, Oxfordshire | Heath Hayes, Staffordshire | Hednesford, Staffordshire | Chipping Norton, Oxfordshire | Adderbury (Nr. Banbury), Oxfordshire | Lydney, Gloucestershire | Knaresborough, North Yorkshire | Saltburn-By-The-Sea, Cleveland | Hebden Bridge, West Yorkshire | Churchdown, Gloucestershire

I'm not very tech-savvy, though I admire those who are. I hate spam, and used to get lots of it. Here's my fixes.

My ISP makes Brightmail spam filtering available to all users at no cost... if they opt in to it. All Brightmail's catches are held in a spam folder until you get round to reviewing and deleting them. It takes a couple of clicks to wipe out a dozen spams.

Anything that gets through Brightmail then is filtered through the Spamcop mail forwarding service I've set up - my ISP allows me multiple email ID's, so I don't download or read the "public" one any more. Anything that's blocked by Spamcop is ipso facto more insidious than the Brightmail harvest, so I happily punish the "clever" spammers by reporting them to their ISPs, web hosts, etc. With Spamcop's "quick reporting" option, it only takes a couple of clicks to report dozens of spammers.

Not much gets through both. If it does, I delete it. The problem's become almost invisible to me.

(I'd still kinda like my own Bayesian filter, though...)

In the UK, we've had satellite broadband for a while, with the Shetland Islands (very very remote) having access to it. In fact the scottish government and northern Ireland Assemblies give a credit against the cost of installation, and IT IS BI-DIRECTIONAL!!!, its also rather fast If your in the UK, you can't get cable or adsl, then try this, though it is from BT openworld Link here, so don't expect it to stay reliable or provide any form of customer support: never try have an arguement with them about postfix, they think its those yellow sticky notes!

footnote: (*) easier done in the UK where static IPs are fairly easy to come by compared to some countries - though most proper ISPs are sensible and check you need them first, some, for example the main telco in the country, pretty much force a /29 on the less clueful of their business customers. (The web page is only one side of it, the salespeople seem to be quite good at pushing this option too). Of course: they can then sell personal firewall software and get you to install a second line if you have >5 users. And don't even get me started on their wonderful trick of restricting MAIL FROM: domains at their SMTP relays (and making sure their dynamic ADSL netblocks are listed in the DUL.....

heres a map of the U.K. now really do you think that broadband can reach most of us ?

http://www.btopenworld.com/broadband/ava61/

really BT need to sort their exchanges out before they offer video on demand via ADSL
(which is their plan after all)

regards

john jones

I've recently got ADSL here in the UK. I've bought it from my old dialup ISP. However, BT provide most of the infrastructure, did the install, and take the lions share of the monthly fee.

I opted for the business service (you can run services, get static IPs, they promise to only oversell the bandwidth by 50%, instead of the 400% on residential etc), which sets me back £100/month ($140/month) for a 512kbps downlink / 256kbps uplink. Every extra 256kbps downwards costs another £20, and you can't start buying more uplink bandwidth until your downlink is at 1Mbit/s.

Initially, I got a static IP thrown in with the deal. I've just gone over to 6 IPs (one for the dsl router, leaving 5 for my boxes), and that was only another £20 / month, but that sort of charge is much higher if you're buying direct from BT

BT Openworld in the UK has been blocking access to Gnutella, eDonkey and Kazaa (and presumably Morpheus) since October on their Broadband (ADSL) service. (someone please respond if these blocks have been since lifted). They also went through a phase of emailing out the Badtrans-B Virus to their customers as well, to keep things interesting, and evicting or restricting customers who have paid for their 24/7 unmetered dial-up service and actually attempt to use it 24/7. Apart from that, it's a great service ;-)

Latest quote (after they had admitted before to port throttling) to customer enquiring if pcAnywhere ports were disabled / throttled: "Erm, we believe that they are not throttled".
They daren't admit it or they'd get hit with litigation, but do it all the same and lose you in the system and charge you £40 a month for the privilege.

I think it's worth expanding here your succinct summary.

They dragged their feet over unmetered internet access via dial-up,

They've always dragged their feet over any innovation that has potential to stop them screwing over customers. They kept ISDN at exhorbitant prices ($640 installation, $42/month rental plus call charges on top). Ran trial after trial of DSL even though they had it working, fearing cheap unmetered access would cut into their lucrative ISDN scam. Even now my friend using BT DSL tells me that the contention ratio is so high his old 56k used to be often faster.

I'm very happy with my NTL cable modem, which is faster (BT caps at 512kbps as does NTL but I get faster downloads and better pings in Counterstrike than my ADSL friends) at half the price.

their network fell over [theregister.co.uk] earlier in the week and they are very reluctant to unbundle the local loop.

In case those abroad know little of BT's history: it used to be a national monopoly and the entire country's telecommunication infrastructure was laid at taxpayers expense. Hence in opening the telecoms market to competition it is felt that rival companies should have the same benefits the ex-monopoly has to level the playing field*. Naturally BT are pulling every legal and obstructive trick in the book to frustrate this process.

Phillip.
* playing fields are of course not level, otherwise the rain wouldn't run off them and you would get lakes in the middle

If you're in the right area you could sign up for NTL digital and get unmetered access free on top of your telly + phone, you might even be lucky enough to get their broadband package for £25 on top of the digital package (making the total as little as £40 for cable telly, phone line rental and broadband).

I wasn't in the right area, so I had to make do with BTOpenworld... £75 install + £40/month for ADSL.

Andy

• I can attest that there are quite a few DSL providers out there who offer megabit connections to their subscribers, but who have an aggregate CO-to-backbone bandwidth adequate to support less than 20% of their subscribers at maximum rate

Want a laugh? BT in the UK offer residential ADSL that is contended 50:1 at the exchange. That's not a typo, I said fifty to one for the upstream bandwidth. 2% capacity. Makes cable seem like a dream.

On the bright side, the service is so overpriced (£40 = $60 a month plus £10 = $15 line rental, perhaps soon to go UP to £50 = $75 a month because "Nobody's taking it"!) that the chances of them ever getting fifty people into any given exchange is pretty low. I don't know whether that's funny or pathetic.

check out http://www.BTopenworld.com/

If you live in one of the first roll out areas this is great. Problem is of course that only 10% of the population do, and some of them won't see anything for another year or two.

The rest of us will have to wait that long just to see when we might expect to get a connection. Couple that with the sparsity of Cable Modem providers and the general lack (or low quality) of free modem access and you find that the uk remains a technological backwater.

The government in all its wisdom wants us all to use the internet and make the uk a leader in e-commerce, but forgets that no one will help them unless they can enjoy the sort of access all you lucky people get in the US.

Anyhow, the Times has this introduction to ADSL in case you haven't heard of it and you can register with BT to be told when they have decided to roll out to your area over here.