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 ...
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)
Composite video (or possibly monochrome luma only)
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 ...
Even just restricting discussion to the first season, before the same people apparently not only clone the PC but also create (facsimiles of) Sierra Online, McAffee, Netscape and Yahoo, she's not based on anybody real.
In real life the source code for the IBM BIOS was printed in the back of the manual. There was no Gordon inexplicably hand transcribing the ...
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:
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 ...
Phoenix Technologies developed its ROM BIOS from IBM's using a cleanroom approach:
To develop its ROM BIOS software, Phoenix claims in its press release
that it used a process that would assure that none of IBM's original
code was wittingly duplicated. One group at Phoenix examined the BIOS
software documented in IBM's Technical Reference Manual, ...
Per Nerdly Pleasures:
... back in the 80s and early 90s, Famiclones were typically made in Taiwan. Frequently they simply cloned the die of the official NES CPU and PPU. At some point, the Taiwanese semiconductor fab UMC made clone chips of the Nintendo/Ricoh 2A03 CPU and 2C02 PPU. They were called the UA6527 and UA6528, respectively. ... This design ...
There's a full clone of a revision 0 Apple II motherboard made by one avid retrocomputing enthusiast.
He no longer has kits for sale, but the board Gerber files are available. Order some boards from a PCB manufacturer, source the components, and you'll have everything to build your own complete Apple II mainboard.
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 ...
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,...
Computer "Composit" (Leningrad+).
Left to right:
+5V 0.6 Ampers
+5 Volts, 1 Amper
There's just one thing though: the Z80 doesn't flip the highest bit of the R register,
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 ...
Measurements of my IBM Model 5150 indicate the badge itself is 1 in. square, equivalent to 25 mm. But there is an additional approximately 1/32 in. added for the indent area, thus allowing the badge to completely reside within the indent.
For "clones", I suppose the ones deemed "100% PC Compatible" would need to match this size, precisely.
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 ...
The MiSTer project is an Open Source effort to create clone consoles/computers on the Terasic DE10-nano FPGA dev kit
They have an Apple II+ core available and the MiSTer can be configured to boot directly into it
The border and multiplied scanline resolution effects would not work properly creating artifacts. The same goes for multitech techniques. Also sound is sometimes affected by this. Other than that no contention means higher speed for code in contented areas at the same CPU frequency. That could lead to crashes in timing critical code. That is the reason why ...
I also found an interesting link talking about differences in the Timex inner-workings about memory/video inner workings here http://comp.sys.sinclair.narkive.com/QIaAtnsk/interrupt-timing-of-timex-ntsc-spectrum-clones
It appear the TC Timex series were more compatible with than the TS, and had the floating bus, hence my confusion. I read something while ...
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 ...