58

I am the author of that video. I wrote a little article about that years ago. I will copy that for you here: Original article here: http://www.zxprojects.com/index.php/the-fix-a-spectrum-blog/29-the-oddities-of-the-inves-spectrum The Inves Spectrum+ was a Spectrum 48K clone made by Investronica, the Spanish partner of Sinclair Research, and responsible for ...


22

No need for any special Spectrum knowledge. It's about power, and there is no rectifying, no appropriate sized capacitor and voltage control elements on this board, so it most definitely does not take AC but rather some well regulated DC input. I'd assume 5V. So operating it at some arbitrary AC and higher voltage my fry it right away. Usually the start ...


13

Looking at the linked schematic and the photo of the internals, I'd say the ports are the following (listed from the reset switch over) Reset Power Composite video (or possibly monochrome luma only) Joystick Tape RGB video The port with the two thicker wires is almost certainly the power, as you identified, backed up by the "upside-down T" symbol on the ...


12

I had two micros when I was growing up: the SAM Coupé and the Acorn Electron. The SAM Coupé has a 512x192 mode much like you discuss. The SAM's display is physically wider than a Spectrum's though, pixels being approximately 1.25 times as wide as tall. The Acorn Electron inherits full 80-column 640x256 video from its progenitor, the BBC Micro. In both ...


11

Only you can decide which port is which as you are the only one with access to your HW. I would use multi-meter and or short circuit tester: Power supply I see no stabilisator nor DC/DC nor AC/DC converters so the power supply is external. Here is first Z80 pinout image I found in Google you can check against any Z80 datasheet. It is look from top side ...


9

Leningrad is a primitive and not particularly compatible clone. However, it is pragmatic, so the incompatibilities are not always going to show up. The main differences are due to a completely different way in which timings are implemented in Leningrad, to an extent that I would not personally call Leningrad's circuitry "an ULA clone". I am a coder, so I can ...


9

In the USSR, the analog TV sets used SECAM, not PAL, so I imagine that the timings will be different between the UK Spectrums and the Leningrad. SECAM is, like PAL just the colour encoding and on top of the basic B&W TV signal. Basic timing is therefore not touched. It's just about how colours are put ontop - which is done in the modulator circuit anway,...


9

Computer "Composit" (Leningrad+). http://sblive.narod.ru/ZX-Spectrum/Composite/Composite.htm http://sblive.narod.ru/ZX-Spectrum/Composite/CompositeSCH-MONT.gif Left to right: KEMPSTON Right Left Down Up Attack/Fire Common TAPE Input Ground Out TV Red Green Audio Out Blue Video Out Ground +5V 0.6 Ampers +5 Volts, 1 Amper Ground Ground Ground ...


8

There's just one thing though: the Z80 doesn't flip the highest bit of the R register, True and so R only iterates across 32k. Not really, it doesn't access 32 Ki but 128 rows. So how does the Leningrad refresh the entire DRAM? Well, like any other machine using 4164 RAMs - by refreshing all 128 rows. It is important to separate address ...


7

From the schematics, I can see this uses a single RAM bank, opposed to the original Sinclair machine, which uses two separate RAM banks. That means that the entire RAM address space must be shared between the video circuit and the CPU, while the original Sinclair machine only shared 16KB of RAM. Now, it happens that DRAMs are not only refreshed using RAS ...


6

The original Spectrum +3 manual has a comprehensive description of the disk format: http://www.worldofspectrum.org/ZXSpectrum128+3Manual/chapter8pt27.html For TR-DOS, it's worth knowing that the .TRD file format is a simple sector-by-sector dump of the disk contents with no additional headers, so any description of the .TRD format (such as this one on zx-...


6

well even old ZX 48K and clones have exposed the AD/DB/CB buses along with /ROMCS signal which can actively disable inbuild ROM. So you can make a small HW that has 16 KByte of SRAM that replaces the ROM with a jumper or switch or programaticaly using some flip/flop and address decoder. This technique is used by any HW peripherial with its own ROM for ...


5

The hardware modifications are possible, and actually already done. The "SuperFoo Harlequin 128" is an all-RAM design based on the original Harlequin that should be capable of running CP/M (Just like the +2 and +3). I haven't heard of someone actually running CP/M on such a machine, but based on its +3 compatibility, it shouldn't be too hard. Some of the ...


5

I think possibly your emulator is fooling you. Per this FUSE feature request, leading to this patch in particular and this commit, FUSE synthesises a boot.b and adds it to the disk directory if you open a disk that does not otherwise have one. So the reason that you can't locate the file within the disk image is that it isn't there. The emulator is ...


4

Look carefully at the docs again (Web Archive one). "The file bodies are stored after the directory entries. Basic program and data array files have an addition at the end of the file." If it is basic program, there are 4 bytes: 2 fixed values 127,170 and autostart line number 0.. 9999. If it is data array, there are also 4 bytes: 2 fixed values 127,170, 1 ...


4

Very little seems to be known about the SPC-650. Apparently it didn't sell well, and ZX Spectrum compatibles were on the whole pretty much overlooked in the far east, excepting Russia. There's a blog which appears to claim that it, and the other clones in the series, has some design and performance changes. It doesn't say what exactly, which makes me think ...


3

It appears that this rumour is in fact false. A video of the commands being run on a real Spanish ZX Spectrum shows that the only visible effect is garbage output.


2

The ideas behind: DRAM access takes place at every CPU cycle. Every other DRAM access (or slot) is for video (further differing between attribute and pixel reads), the rest slots are for CPU. In fact, CPU and video slots simply follow each other in a rigid sequence. As the M1 read signals are active for only 1.5 clocks, the Leningrad phases or 'aligns' each ...


2

I had a Timex TC 2048 (compatible with the ZX Spectrum 48k) with the text extended modes, never used them much. Granted, they were not supported by the ZX Spectrum ROM in the first place and the software to support them was not that widespread; however I got a tasword copy that supported those modes, and in my cheap B/W (PAL) TV the result was difficult to ...


2

Working backwards from FUSE — machine_current->ram.last_byte appears to be the current state of 7ffd and machine_current->ram.last_byte2 is 1ffd: 1ffd:d1 is active high; 1ffd:d0 appears to override d1 — d1 selects which ROM would be visible in the usual ROM area if ROM were selected; d0 determines whether ROM or RAM is selected; d1 does sit in front ...


1

The usual way of such HW peripherials was switching the original ZX ROM (0-16384) chip for its own memory space where was usually another ROM or even RAM on the runtime. It was done by the /ROMCS pin on the extention bus/connector. I am not famillair with TR-DOS as I was heavily using MDOS instead. The MDOS was an ZX OS extention for Didaktik D40/D80 ...


1

TR-DOS Files themselves have no header at all. Metadata is stored in the directory section of the disk, along with the filename. The metadata has a type field, which is also the file extension. Depending on this field you interpret some of the other fields in different ways. "B" for Basic programs. "C" for machine code, or any binary file ...


1

Use the schematics http://speccy.info/%D0%9B%D0%B5%D0%BD%D0%B8%D0%BD%D0%B3%D1%80%D0%B0%D0%B4_(%D0%BA%D0%BE%D0%BC%D0%BF%D1%8C%D1%8E%D1%82%D0%B5%D1%80) to trace everything up to the connectors. Any other way would be just guessing. You can power the board from any widespread USB charger, 2A would be enough. Trace common power pins (ground: pin 7 at any DIP14 ...


Only top voted, non community-wiki answers of a minimum length are eligible