Spectrum Computing

Your machine is a 48K, the DRAM slots in the lower right are all populated. It sounds like it was sold to you as a 16K because the upper RAM isn't working? You might still be able to load a 16K game, though. What device are you using to play the tape? Spectrums require significant volume from the ta...

That's really interesting, I've never heard of a CPU NOP tester...

And, once past the 4-pixel position, ... And excuse my ignorance as well, please, what is the 4-pixel position? The original thread suddenly started talking about 4 pixels, which didn't make sense to me because attributes are aligned to 8 pixels. Hence I lost track of that discussion. But clearly 4...

Some issue one and some early issue two boards have extra daughter boards to correct I/O contention issues. This was then incorporated in later issue ULAs. Some may have escaped modification... Is that what's going on here ? I noticed that auction yesterday, and was rather surprised to see an uncas...

PROSM wrote: ↑Tue Jan 30, 2024 11:53 am again, this has been a fruitless endeavour.

Nevertheless, I am in utter awe of your audio signal preprocessing abilities...

SkoolKid wrote: ↑Fri Jan 26, 2024 11:50 am And now I have an import duty/customs clearance bill of over $100 to pay before I can receive the package.

You would have always expected that, though, would you not?

Many thanks for all the help. I'm using an RP2040 attached to the edge connector to sample signals and understand what's going on with the CLK line. Nothing is taking over the machine, and the Spectrum isn't expected to be doing anything useful while I conduct these experiments. I was seeing odd val...

Thanks Mark. Unfortunately, in my attempt at brevity, I didn't quite ask the question I wanted to, which was this: If I assert the Z80's /RESET pin (via a device on the Spectrum's edge connector), and hold that /RESET pin asserted , am I guaranteed that memory contention will never happen and the UL...

If I assert the Z80's /RESET pin (via a device on the Spectrum's edge connector) am I guaranteed that memory contention will never happen and the ULA will never slow the clock from 3.5MHz?

If it's the chip that handles data bit D0, D1 or D2, that's enough for the ROM memory check to fail the 'upper' RAM, the machine should then try to operate as a 16K system. Would it be adequate to clip the data pin on the upper DRAM chip which supplies, say, D0? The system would then see that bit a...

You're doing everything right. My conclusion from my own attempts to get those ICs out is that sometimes, quite often in fact, it's just not possible. A desoldering gun is more convenient than a solder sucker, but it's not a magic weapon. The problem as I see it is that when the IC was inserted, its...

So, booting with the external ROM card sees the Spectrum come up normally? The video seems to demonstrate that? Is the machine stable for that minute or so, in that you can type stuff and make it BEEP, etc? If it seems OK, then that seems to point to a building heat issue. Can you find any device wh...

- then i put an lower memory ic backwards and things got worse so i ordered the lower ram board that replaces the ics Just to be clear, you put a 4116 in with the wrong orientation, then powered up? That would have connected +12V through that IC and to goodness knows where. You might have fried par...

Are any of the major components in sockets? Popping out any that are would be an obvious first step.

All those little sounds are being sent to the chip a little per frame, but I've no idea HOW to make sounds... Several times you've referred to "the chip" which makes me wonder if you understand how the 48K machine makes sounds? It doesn't have a chip. It has a speaker. When you send a log...

Retroleum are always highly regarded:

https://www.retroleum.co.uk/keyboard-parts-spectrum

Their kit gives you a soft plastic wedge ideally shaped for raising up the faceplate without damaging it, which saves you searching for something suitable in your drawers.

dfzx wrote: ↑Fri Dec 15, 2023 10:50 am I'm currently counting 21 of them for sale on ebay, all inside 24 hours.

There are now 42 Nexts listed on eBay. Only about half a dozen have sold in the last few days. If anyone wants one, now might be a good time to try an offer.

Mine has arrived but isn't being opened for another week.

_dw wrote: ↑Sun Dec 17, 2023 8:34 pm I'm not good enough for C.

Well that's fair enough. But then it's not really fair that you criticise the language when you readily admit that the language isn't the actual problem. Unjustified and inaccurate criticism just puts potential users off.

Selling variables via the stack even if recursion is not used is simply expensive, so then I try to make various exceptions to selling via registers, but this can only work if the function no longer calls another non-recursive function. Then the variable must be cleaned up on the stack or in memory...

ketmar wrote: ↑Sun Dec 17, 2023 2:13 pm that's why. i literally replied to OPs question in full with my very first message here.

Oh I see. Your opinion on modern Z80 C is based on your experience with HiSoft C for the ZX Spectrum from 1984. Yes, that explains quite a lot.

it is just an example of complex app. ok, let's take another one: scriptable text editor, for example. again, i can fit it into 16 kb (prolly even less), with fully-featured compiled language inside. but i know, this, again, is not the task we're doing today. actually, any more-or-less complex task...

but try to write something else and complex with Z80 C — like, for example… native C compiler — and you'll see how useless Z80 C is. ;-) No you won't. Z80 C isn't useless. Lots of good software has been written in it. Z80 C is excellent for a whole bunch of tasks. and ZX Forth compiler can be about...

If anyone so much as mentions C on the Spectrum Computing forums our little band of C-haters will immediately pop up and pronounce what a terrible language it is, how badly it works on the Z80, how recursion is a problem and how anyone interested in C should definitely be learning Forth instead. Tak...

I'm currently counting 21 of them for sale on ebay, all inside 24 hours. Hard to see those rather optimistic £700 - £1,000 buy-it-now price tags being met much longer. Which is good. I appreciate people ordered their machines 3 years ago and many people's circumstances have changed, but it still rat...

Why was it used for the fuse emulator? That's the ROM bundled with the Debian FUSE package (Ubuntu is based on Debian) because Debian is rather hot on only using freely licenced code and material. The 1982 ROM isn't distributed under any free licence so Debian needed an alternative. If you don't in...