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24 votes
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Who were the first engineers to "cleanroom" the IBM PC BIOS?

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 ...
Tommy's user avatar
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23 votes
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Which ports are which on this Soviet ZX Spectrum clone?

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 ...
Raffzahn's user avatar
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20 votes

Who were the first engineers to "cleanroom" the IBM PC BIOS?

It was a team of engineers at Compaq and it cost the company $1 million, before it even had any other product to sell, so you can be sure it's well documented by Compaq who did what. It was a big ...
El Profesor's user avatar
16 votes

Who were the first engineers to "cleanroom" the IBM PC BIOS?

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 ...
snips-n-snails's user avatar
14 votes
Accepted

How compatible is the Leningrad clone with the "original" ZX Spectrum?

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 ...
introspec's user avatar
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13 votes

Which ports are which on this Soviet ZX Spectrum clone?

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) ...
mnem's user avatar
  • 4,517
13 votes

Build a hardware clone or emulator of Apple II?

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 ...
RETRAC's user avatar
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11 votes

How compatible is the Leningrad clone with the "original" ZX Spectrum?

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 ...
Raffzahn's user avatar
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11 votes
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Large number of Famiclones

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 ...
Tommy's user avatar
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11 votes

Which ports are which on this Soviet ZX Spectrum clone?

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 ...
Spektre's user avatar
  • 7,218
10 votes

What computer is this, a clone of a ZX Spectrum?

Judging from the block graphics on the number keys, this computer is a ZX Spectrum clone. On the 8 key, it's a solid graphic, and on the 7 key it's filled in in the lower left corner. This is ...
Omar and Lorraine's user avatar
10 votes

When was the end of the floppy-only IBM PC clone?

The question seems to ask for several different points in time: When the floppy based PC was no longer a default option When application software (games) no longer worked from floppy alone When PCs ...
Raffzahn's user avatar
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10 votes
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How does DRAM refresh work in the Leningrad?

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 ...
Raffzahn's user avatar
  • 213k
9 votes

Which ports are which on this Soviet ZX Spectrum clone?

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 ...
A. Rumlin's user avatar
  • 361
8 votes

What was the standard size of a PC clone's badge indent?

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 ...
Brian H's user avatar
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7 votes

How does DRAM refresh work in the Leningrad?

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 ...
mcleod_ideafix's user avatar
7 votes

Build a hardware clone or emulator of Apple II?

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 ...
jamesfmackenzie's user avatar
6 votes
Accepted

When was the end of the floppy-only IBM PC clone?

From memory of personal experience and in the UK... For the general public, about 1988-1989. For home PCs, I had a fairly large PC-buying and family-age community around me at work then. By those ...
TonyM's user avatar
  • 3,485
4 votes

When was the end of the floppy-only IBM PC clone?

Probably in the nineties (obviously, there won't be any "hard date"). One major development that marks the shift to hard disk-based PCs might be the introduction of "hardcards" - ...
tofro's user avatar
  • 33k
4 votes

When was the end of the floppy-only IBM PC clone?

Exception: Networking PC networks are an interesting thing. With many variations, of course, they have evolved over the years from largely traditional client-server (cheap workstations, expensive ...
manassehkatz-Moving 2 Codidact's user avatar
3 votes
Accepted

What was the standard size of a PC clone's badge indent?

One inch square, I think (at least, the insets on my old, beige, midi-tower cases are).
Mick's user avatar
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3 votes
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Timex 2048 RAM contention ULA/video output

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 ...
Spektre's user avatar
  • 7,218
2 votes

Timex 2048 RAM contention ULA/video output

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-...
Rui F Ribeiro's user avatar
1 vote

When was the end of the floppy-only IBM PC clone?

My suggestion is to look through newspapers starting around 1988 and moving forward. I remember "The Toronto Sun" paper was basically a computer advertisement tabloid at that time and the ...
Boomba Jinga's user avatar
1 vote

When was the end of the floppy-only IBM PC clone?

Your question is a bit mixed up. Many applications needed a hard drive to run but loaded from floppy disks. I think Windows 2 did this let alone some of our internal software, and programs written in ...
mmmmmm's user avatar
  • 181
1 vote

Which ports are which on this Soviet ZX Spectrum clone?

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 ...
lvd's user avatar
  • 10.2k

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