29

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 ...


19

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 ...


16

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 ...


13

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 ...


9

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 ...


6

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 ...


5

A loud click at beginning/end of the sound, but faint sound inbetween might be caused by a failed DC blocking capacitor. According to the gameboy schematics found at http://www.devrs.com/gb/files/gameboy1.gif, there is a 100µF capacitor in series with the speaker. If this is indeed the case, sound should be working fine at the headphone jack, because it uses ...


3

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 ...


2

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 ...


2

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. ...


2

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 ...


1

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 ...


1

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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