Spectrum Computing

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...

I've added the following to the home page: Please note that you can't search for X-rated via this site. They are not omitted from ZXDB though, so we suggest you use a site like https://zxinfo.dk/ to search for such titles. Actually, what you've added to the home page says: Please note that you can'...

What about flight simulators? We don't discuss those much on SC, and I've never come across a disassembly of one. But surely they employ the laws of physics, at least to some extent?

Jbizzel wrote: ↑Fri Dec 01, 2023 11:48 pm Gravity my boy.

But MM doesn't use gravity. The jump is just an up-and-down animation. The falling is just incrementing Y by a set amount. I suspect the vast majority of platformers don't use any rules of physics or any sort of gravity equation.

berarma wrote: ↑Tue Nov 28, 2023 3:31 pm ...there aren't many games involving physics in a meaningful way.

I loved Sagittarian Pinball BITD. There was also a game of pool I really liked, I think it was this one, but 40 years might have blurred my memory somewhat. But you asked for puzzle games, and neither are.

The problem with some some Spectrums' Z80's /M1 lines not working is well known, but I recently noticed this blog post from Tynemouh Software: http://blog.tynemouthsoftware.co.uk/2017/07/z80-m1-signals.html He says: "However, if you look at the ZX Spectrum edge connector, M1 is right next to th...

According to the DRAM waveform, data are supposed to be available on lowering /CAS. No, that wouldn't make any sense. /CAS goes low when the second part of the address (the column address) is on the 7-bit address bus. The memory then has a certain amount of time to fetch the data byte and put it on...