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Comment by yuhong | Hacker News Reader

FYI, it was 8253 in PC and XT, 8254 in AT. The main difference is the readback command I think. This is not the only error in this blog post BTW.

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Author's reply concering that:

Back when I made that post I thought it was an 8253. But I checked the sources for the function that Beep.Sys uses to program the timer and it claims that it’s an 8254 so I went with the source code.

How hard would it be to use the chip? Not hard but now that Win7 has shipped, the number of machines with an 8254 that’s actually wired to something is going to dwindle to around 0. The machines will still have an 8254 (it’s on the SuperIo chip in every PC) but it won’t be connected to any hardware.

Yeah, saw a motherboard like this a couple of years back when I was helping a friend build a new PC. We couldn't get it to boot even to the BIOS and started looking for the POST codes. There weren't even pins to attach a speaker to, just nubs on the board. Nor was there any sort of LED indicator. I ended up having to read the POST codes using a multimeter. That was a fun day.

There is another error in this reply. It is in the southbridge not in the Super I/O.

The SuperI/O is the part of the southbridge (which later became the ICH and nowadays is known as PCH) that implements the legacy ISA chips (RTC, 8042[1], 8254, 8257, 8259). It used to be separate, which was already an improvement over the separate integrated circuits of 30 years ago.

[1] nowadays the 8042 is mostly emulated in SMM because it needs to convert USB to PS/2.

I think the Super I/O is typically a separate chip on the LPC bus.

Not since at least PIIX (1990-something).

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