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Some time in 1977 or so the X1 register on the CDC6400 at Northwestern's Vogelback computer center failed. Gobs of files got corrupted. The on site CDC engineer was able to repair the machine (don't know if he replaced the transistor or the module). Unfortunately the backup system had been misconfigured so files couldn't be recovered. The center was shut ...


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Slightly bananas answer: MC68000. Okay, I know, it's not a graphics chip. But, you can take some inspiration from the Xerox Alto, which would presumably have been a somewhat familiar source of inspiration to somebody working in graphical workstations in 1980. Since the Alto didn't have access to a modern off the shelf RAMDAC for displaying the contents ...


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is it possible Yes, but what would it add to a 2D sprite/blitter with masking (aka transparency) ? Basically those are tiles. Some sophisticated hardware could have some notion of priority between those tiles to choose which one to display "on top" of the others. And maybe handle collisions (only useful between field objects). That would be an improvement. ...


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One nuance to the Pentium 133 is that it used precharge, domino logic (please correct me if I am wrong; I recall this from an Intel presentation). This logic requires a minimum speed to operate. This minimum speed is one reason that you could not have a legacy "turbo" switch change the speed, because it would violate the logic timing, which you could ...


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386 and some early 486 board had still a Turbo button that slowed down the CPU speed. I had a Vobis 386 computer that had an 8 MHz/25 MHz 386. From what I recall in the manual was explained that was for reading copy protected floppies or software that didn't work at the higher speed.


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IIRC at the time cheaper cases were sold as XT/AT cases and in addition to taking AT motherboards had the mounting holes and turbo switches for old XT motherboards years after people stopped buying them new, while newer AT only cases were slightly more premium. Also some newer motherboards would still have a jumper to accept a turbo switch and would slow ...


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The purpose of the switch is to support CPUs that can work at different clock frequencies. However, the presence of a turbo switch and a frequency display on a case, do not necessarily imply that the CPU can actually work at different clock frequencies, because the case is a generic case which has not been designed for one specific CPU. Background I ...


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Your premise that the point of the Turbo button was originally to slow down the computer to be timing compatible to an IBM PC/XT is correct. There was demand for that function, because a some of software, mostly games, were not synchronized to any timing source, but just scaled with the CPU frequency. some examples I encountered at that time are: Bugs, 1982 ...


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I thought the whole point of the turbo switch was to enable compatibility with games that expected 4.77MHz. What was the purpose of the slow/fast turbo setting on PCs whose CPUs could not slow down to 4.77MHz? The turbo switch lost that purpose much earlier. It did that job on 8088 PC compatible machines runing at slightly higher clock speeds (in the 8-10 ...


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I thought the whole point of the turbo switch was to enable compatibility with games that expected 4.77MHz. A very similar question was already asked here. One answer was that the "Turbo" button was often used for other purposes (such as switching an additional fan on or off) by users whose motherboards did not support the "Turbo" button. When there were ...


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TL;DR; Looking at the linked board manual reveals that it doesn't support any 'turbo' switch. So this is simply a case having it, while there is no purpose - maybe except for the fun of having a button that switches the illuminated segments :) It might be safe to assume that the board has been updated or the case been used regardless. After all, why throw ...


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The amplifier input is biased to about half supply voltage. The SID output is also biased to about half supply voltage. You have little or no bulk/bypass capacitance on the 9V supply pins, so abruptly disconnecting the 9V supply from amp also abruptly shuts down the amp input bias. But as you have the quite excessively large 22uF coupling capacitor between ...


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This sounds like an ESD/over voltage event might have occurred while you were working with the circuit. The SIDs are extremely sensitive. It is not uncommon for a defective SID to draw excessive current. (This is not going to bring back your SID, but just a tip for future work: while prototyping your project, consider using a SwinSID (Nano) instead - it's ...


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The Commodore SID chip has two paddle inputs; the C64 can support four paddles by multiplexing between the paddle ports on the first joyport and those on the second. See https://archive.org/details/C64-C64C_Service_Manual_1992-03_Commodore/page/n15/mode/1up for more information [link courtesy cjs].


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A second bite of the cherry: amongst others, the WD177x family are popular floppy controllers that were used in or with a variety of 8-bit machines including the MSX, the Acorn Electron and later models of the BBC Micro, the Oric and the TRS-80. They are serial controllers because floppy drives provide a single data line, which the controller monitors for ...


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In the Commodore 16/116/Plus-4, the Cassette connector and the serial (floppy and printer) port are both implemented via the CPU's single built-in I/O port which can be accessed by code at addresses $0000/$0001 (the same port that is used for the bank switching logic in the C64). Most lines of the two interfaces use separate bits of that one 8-bit port, but ...


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The Sinclair ZX81 had a single Uncommitted Logic Array (ULA) chip that controlled both the screen and the cassette port. Consequently, accessing the cassette (loading or saving) would cause stripes to appear on the screen. It also controlled the keyboard, causing the screen to flicker at each keypress, but the keyboard was built-in and so it doesn't count ...


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The NES with its multitap accessory is a potential answer, if you'll accept some logic in the accessory. NES controllers use a 1-bit serial protocol. The host strobes to begin a transfer, causing the joypad to load its current state into a shift register, and the host then clocks in 8 bits, each representing one of the 8 inputs. It's actually the CPU that ...


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The Sinclair QL also had two RS232C ports which used an unusual combination of a ASIC (ZX8302) and Intel 8049 to provide two physical ports (with non standard connectors) but could not be used independently. The two ports were nominally for printer and modem use, but during development the built in modem of the QL was dropped, but the case retained the ...


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I think the canonical example from the 16-bit era is the two ports on the Macintosh provided by a single Zilog 8530 and able to be used for serial, printer, modem, and AppleTalk networking based on user configuration. Of course this was influenced by the modem and printer port on the 8-bit Apple //c, but those ports relied on 2 independent 6551 UARTs. In ...


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The Commodore 64 used a single CIA for both the keyboard and joystick (or paddles). This made reading both the keyboard and the joystick at the same time a bit of challenge, see this answer for details (complete with schematics). As for an explanation of "why", I guess the answer is always "to save parts and make it cheaper".


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