* Posts by deanb01

43 publicly visible posts • joined 31 Oct 2014

The chip that changed my world – and yours



I guess this is why the eZ80 is so called - it's not E-ZED-EIGHTY, it's E-ZEE-EIGHTY (Easy 80).


Re: eZ80?

The eZ80 is an interesting chip - it's binary compatible but not a drop-in replacement, even if a suitable adaptor board was available. For example, it has a three-stage pipeline which means that the same code running on an eZ80 clocked at the same speed as a Z80 will run much quicker. As a lot of code on retro computers is timing critical, then this would cause issues.

And it operates at 3.3V rather than 5.

So in the long term replacements for retro computers (ZX81, Spectrum, MSX, Amstrad, etc) will no longer be available as new stock. And there are many new boards that use the Z80 (RC2014, Microbeast, etc).

The eight-bit Z80 is dead. Long live the 16-bit Z80!


Re: the Z80 is a simple chip by modern standards and is easy to implement on an FPGA

You'd have to throw in a bunch of level shifters as the Z80 is 5V, FPGAs are typically 3.3V.


Re: Agon eZ80

I owe an immense debt of gratitude to R.T.Russell who wrote the original Z80 version and who kindly open sourced it a few years ago. I've ported it to a handful of computers since, including the Spectrum Next, Cerberus 2080/2100 (also by the creator of the Agon, Bernardo Kastrup), and my homebrew Z80 computer. Thankfully Richard's source code is very easy to work with. The 16-bit version took a weekend to port over. The 24-bit version is still a work-in-progress - currently refining the inline assembler to handle eZ80 mnemonics.


Agon eZ80

As the author of the original Agon Quark firmware (you linked to my Git) and long time Z80 developer, I've grown to like the eZ80. It has its quirks, the most annoying being that there is no straightforward way to access the top 8 bits of 24-bit registers without storing the register in memory first. Yet that not withstanding, being able to access more than 64K without paging is incredible, and the three-stage pipelining means that most code without modification runs much faster. It's also got some neat extra instructions such as MUL. And the C compiler, provided by Zilog, works quite well on it.

It implements kind-of-backwards-compatibility by letting you run a standard Z80 program in a 64K page in memory - the Agon allows the user to run older 16-bit apps in a 64K page or 24-bit apps. I ported the first version of BBC BASIC for Z80 by R.T.Russell originally in 16-bit mode with very few modifications (the full-fat 24-bit version required much more work - source on my Git if anyone is interested).

And it's a complete Z80 SOC with DMA, UARTs, timers, etc.

That all notwithstanding, one can't beat the original in its 40-pin DIP package!

Zilog to end standalone sales of the legendary Z80 CPU


Re: Perhaps the most peculiar use for a Z80 I've seen...

Oh, I've got one of those in a drawer somewhere. Didn't realise it was based on the Z80!


Gameboy Z80

Slight correction to the article - the Gameboy CPU isn't techniclly a Z80, it 's a Sharp LR35902. Whilst it's Z80-like, it is severly cut down, lacking several key features such as the alternate register set, block instructions (LDIR, etc), 16-bit addition/subtraction and index registers (IX/IY). It does add an 'FF' page, which is a bit like 6502 zero page. Though the point made is taken. as stocks dwindle it will become more difficult to source known working parts to replace Z80s in Spectrums, Amstrads, MSX machines, and so on.

The New ROM Antics – building the ZX Spectrum 128


Stories give context

The retro community are brilliant at reverse engineering hardware, scanning schematics and preserving software. Stories like this are often not that well known. I've often felt we need to get better at recording details like this now - none of my generation are getting any younger, and they may soon be lost forever. They may seem inconsequential, but they do give context.

Microsoft Defender ASR rules strip icons, app shortcuts from Taskbar, Start Menu


There's your problem, right there

Yep, our org had the same problem on Friday. I was the first to notice it / unlucky to get the definitions installed, so my laptop was used as the guinea pig. Thankfully I'd noticed that Defender had been popping up more notifications than usual, so we quickly isolated the problem, the offending rule was disabled, and I was then left with the task of fixing up my shortcuts. Sigh.

UK politico proposes site for prototype nuclear fusion plant


It's spelt 'Nucular'

I also heard on the grapevine that the next generation of warp engines will be built in County Durham.

Beware the fury of a database developer torn from tables and SQL


Bodge City

Worked for a UK based fruit machine manufacturer a few years ago (Barcrest) that was purchased by a US gaming company (IGT). I was the sole developer on a project to put some more interesting aesthetics on their frankly dull one armed bandits. This involved replacing the neon-tube light box above the game with one that had its own CPU. The Barcrest code was a mixture of Forth and 6809, so plenty of voodoo involved.

Got ushered into my bosses office at a later date with regards to my source code. Apparently the Nevada Gaming Commission took a dim view of some of the comments in my code, for example:

; Entering Bodge City in a bus with no brakes

In my defence, I wasn't told my source code would be submitted.

Windows 10 installation shows shopping centre its sad face – the natural response to finding out you're in Peterborough


That was a unit my previous employers installed...

Ah that takes me back. I was part of the team responsible for those units. The company in question went bust around 4 years ago, and I've moved on from designing digital-out-of-door screen systems.

It originally shipped with a PC running a cut-down Linux distro (desktop stripped out, etc) for the big screens. Later versions ditched PCs altogether and ran custom playout software on a Raspberri Pi. One of the reasons for that decision was to avoid this scenario. The other was cost.

ZX Spectrum reboot promising – steady now – 28MHz of sizzling Speccy speed now boasts improved Wi-Fi


A good effort

I decided not to back this first time around given the Vega debacle, and kicked myself afterwards. The Next is a very capable machine; not just an enhanced Spectrum that can run Spectrum software and most peripherals, but can also masquerade as other machines, such as the BBC, CPC, and even arcade boards by flashing the FPGA with an appropriate core.

Credit to the Next team for pulling this off, despite the bad tax advice and having to top up the funds to achieve the initial launch out of their own pockets.

Needless to say, I've back this second round, and will look forward to receiving mine next year.

Openreach's cunning plan to 'turbocharge' the post-Brexit economy: Getting everyone on full-fibre broadband by 2025


2025? Hahahahahaha! No wait. Hahahahahahahahaha!!

They've not managed to run FTTC to half the houses on our estate in South Manchester. As a result, I'm still on ADSL+

The safest place to save your files is somewhere nobody will ever look


Porn Stash

I ran the IT department of a small marketing company 'back-in-the-day'. We had a call from a member of staff who was struggling with a sluggish company laptop. So my PFY called him and remoted onto his desktop. Part of the process involved clearing out the trash; clear cache files, delete tmp files, and so on. The PFY opened up the wastebin and it was set to display the folder as thumbnails. The pictures were, well, quite hardcore porn. The PFY took it in his stride and, whilst talking to the user, said "I think we'll close that, shall we?". After a lot of mind-bleach, we raised it with the directors, who took a dim view, and fired the chap on the spot.

UK's Openreach admits 50k premises on 'gigabit-capable' FTTP network can't get gigabit speeds


Absolute shower

BT seem to half-complete jobs, then move onto the next technology. I'm still waiting for FTTC on our street, in a suburb close to Manchester. The exchange is digital, and half the estates streets have been converted. Seems BT reached some internal target to state that our village is now 'Digital' and moved on. I'm a homeworker stuck on ADSL+ - refuse to get Virgin, the only other option, as neighbours report theirs going down on a regular basis, and their modems suck. Seriously considering 5G when it reaches us - heck, even a 4G connection would be better than what we've got at the moment.

Openreach names 81 lucky locations to be plugged into its super-zippy Gfast pipe



Still stuck on ADSL+ here in South Manchester. Neverreach can't be bothered to put in the remaining street cabinets so our part of the world can benefit from the lovely fibre-enabled exchange just down the road.

Bright spark dev irons out light interference


Spark plugs on old Vauxhalls

Back in the day, when you got a mono MW/LW radio thrown in as a luxury item on Vauxhall Nova's standard equipment I noted on mine that there was a connector between the HT leads and the spark plugs. According to my dad (who was a Vauxhall mechanic) this was a choke to reduce radio interference from the HT wiring.

Python joins movement to dump 'offensive' master, slave terms


Better inform the car manufacturers

There are other uses of master / slave in systems. For example in cars (clutch and brake master/slave cylinders)?

10 PRINT "ZX81 at 37" 20 GOTO 10


Re: Display Memory

It's also possible to fool the display routines into producing a pseudo high-resolution image.


Bizarrely the ZX81 did not have an error code for a failed tape loading (just checked my manual). That was introduced on the Spectrum. I think the ZX-81 just stuck in the loading routine.


Fond memories

Cut my programming teeth on a ZX-81. Despite it's basic configuration it was a great little micro. The literature in the early 80s was fantastic, and the hardware was simple, so it was quite easy for your average 10-12 year old to pick up a little bit of assembly language or indeed a basic knowledge of digital electronics (the ZX-81 was also available in kit form for the more adventurous).

The manuals for the ZX-81 and Spectrum still hold up as being an example on how to write a technical manual for the layperson.

I remember it being a bit of a pain to write assembly language on it - there being no facilities to store or reserve memory for the code. The solution was to store the code in a REM statement at the top of the code. I must have worn out the tips of my fingers creating REM statements with sufficient characters in to store my code.

Thankfully, by the time I came to do serious coding (games) the Spectrum had come along, and you could reserve the top of memory for code.

1K was a challenge - 16K seemed like an absolute luxury at the time. I still write code with memory and efficiency in mind, despite the best efforts of bloatware runtimes.

Still got my ZX-81 and fire it up occasionally for old times sake.

Openreach ups investment plans: Will shoot out full fibre to 3 million premises


A press release designed to impress investors...

...Still waiting for them to enable our cabinet for FTTC. Only been waiting 3 years. Suspect we'll get passed over for FTTH for the same reasons - it costs to dig trenches.

Well done, UK.gov. You hit superfast broadband target (by handing almost the entire project to BT)


95% of statistics are made up

So our exchange is FTTC yet less than 50% of the cabinets in the surrounding estates have not been converted. BT / Openreach seem to have a thing for counting a town as 'converted' once they've done the exchange, regardless of whether any of the population can get the service. It's all ballcocks.

'Mummy, what's felching?' Tot gets smut served by Android app


True Story

Back in the day, a new guy was being introduced around the company I worked for. All was going well, until he arrived in the developers room. He was introduced by the boss, and one of my colleagues started laughing so hard he nearly choked on his coffee. He only told us why after the guy had left the room.

The new guy's name was Phil Ching.

Itching to stuff iOS 11 on your iPhone? You may want to hold off for a bit


App Store still thinks it's in beta

Tried to leave a review of an app on the new App Store and got an error message saying I could not leave reviews on a pre-release version of iOS. Oops.

Atlassian kills God, rebrands as a mountain, a structurally unsound 'A' or a high five


That was clearly worth it.

Been using Jira all day and wouldn't have noticed the change of logo but for this article

UK.gov unveils six areas to pilot full-fat fibre, and London ain't on the list


Beg my scepticism...

Openreach will do what they did with FTTC - target the low hanging fruit then declare the project a success, like they've done in many towns in South Manchester.

Talk about a hit and run: AA finally comes clean on security breakdown


Re: GDPR (as of May 2018)

I use Microsoft Authenticator with HMRC online services. Pretty sure it works with Google Authenticator too; only use MS for Office 365.

Worry not, Python devs – you can program a quantum computer



Might be missing the point here, but isn't Scratch adapted from Smalltalk, not Python?

Meet Hyper.is – the terminal written in HTML, JS and CSS



Just visited the website to see if it would shed some illumination as to the point of this project and have come away from it none the wiser.

First World Problems: John Lewis clients forced to re-register after website 'upgrade'


Nothing to see here...

I've got a partnership card and received an email on the 7th Oct that clearly stated I had to reregister.

You've seen things people wouldn't believe – so tell us your programming horrors


True or False

Whilst working in the software department of a well known fruit machine manufacturer, I was introduced to the following piece of logic. I think it was in C, but the gist was:

if(a == true) {

b = false;


else {

b = true;


Scout Association's shelved database won't be back until next year


Compass Bearings

I use OSM and am dreading the the return of Compass. Nothing like having to use two online systems to manage your group and having to train other non technical section leaders to eat into your spare time.

BT boss: If Ofcom backs us, we promise to speed up UK broadband


Doing the bare minimum

According to this press release https://www.btplc.com/News/Articles/Showarticle.cfm?ArticleID=D6BA16C8-6876-4735-B571-C1DAD61512A0 I should have FTTC Superfast Broadband. Oh wait, they only appear to have converted less half of Gatley's cabinets...

We're hardly out in the sticks, less than 10 miles from the centre of Manchester and 3 from Stockport.

Similar story when fitting out remote offices for work. More than half are only served by ADSL. Broadband in this country is a mess.

Scientists love MacBooks (true) – but what about you?


Works for me

Purely a practical choice for me.

I've got a late 2013 15" Macbook Pro I purchased from Apple's Refurbished store. Got last years model and saved my company £340. At that point it was cheaper than the equivalent Windows PC.

It spend 90% of it's time booted in Windows 7 with occasional forays into OSX. I'm a software developer working on a mixture of Windows and Linux systems with some multimedia work & app development mixed in. It has its quirks, but so far has been the best laptop I've owned, mainly down to the screen resolution.

All right, who guessed 'street mapping' for those mystery Apple vans? Congratulations


Bah humbug

Why stop at two global companies reinventing the ark? Anyone else fancy driving cars around the entire planet to street map it?

Openreach to trial G.fast in Swansea


Re: Come the revolution...

Brilliant!! We've now got a new name for Openreach in our office now. Thanks :-)


Come the revolution...

Shame Openreach can't get FTTC broadband to our estate in Gatley, South Manchester. I get a faster Internet connection through my mobile phone. Also this year I've set up 7 regional offices in Preston, Norwich, Blackpool, Stockport, Wilmslow, Carlisle & Birmingham and Openreach can only serve "Superfast Broadband" to 2 of those. Not seeing much of a broadband revolution in the UK at the moment.

RAF radar station crew begs public for cash to buy gaming LAN kit


The Stark Truth

Fair play to them. Even S.H.I.E.L.D agents get to play Galaga whilst on duty.

Euro broadcast industry still in a fug over that 4K-ing UHD telly


My eyes are hardly HD quality, let alone 4K.

What time do you call this, BT? Late, state-funded broadband rollout plods on


Half-arsed broadband rollout

Unable to get fibre broadband on the A6 in Stockport to a new satellite office my company is setting up and my home in Gatley, despite the exchange being capable of it, is not fibre broadband ready as BT have only put cabinets on half our estate.

About time BT/OpenReach/Gov pulled their finger out IMHO.

One hard ghoulie: 1985's Ghosts 'n Goblins


Great game!

I worked at Software Creations during that era and developed the Amstrad CPC version of Ghouls n Ghosts. A beggar to program on 8 bit hardware and not my finest work. My colleague, Mike Follin, programmed a technically excellent scroll routine on the Speccy version, derived from earlier work on Bubble Bobble & LED Storm, that "chased the raster' to run at 25fps and draw sprites and backgrounds on alternate frames without flicker.

The Speccy version of Ghosts n Goblins was a great game for the time & really pushed the Spectrum to its limits.