Talk:MOS Technology 6502/Archives/2019

How many have been produced so far?

According to minute 3:00 of this talk on YouTube, more than 10 billion were produced by one company alone. It would be nice to have a proper source for production numbers (presumably of the entire 65xx family) so the information can be included in the article.

Name of stack pointer

"SP" is common usage for other machines, but the hardware data sheet agrees with the text, which refers to it as "S". TEDickey (talk) 02:11, 8 November 2019 (UTC)

OK although my extremely dim recollection is that "SP" was common. At any rate, whoever created the table certainly thought "SP" was right because they helpfully bolded the full name (Stack Pointer) in the same manner done for PC. It is true that the instruction set includes TXS which uses S and PHA is defined in terms of S. Johnuniq (talk) 04:13, 8 November 2019 (UTC)

The designers needed registers to have single-letter name if they're to be used in the instruction mnemonics that they'd fixed at three letters. PC isn't so they could go with convention. SP is so that may be why it's only S. My opinion of the datasheet at the time was that two letter names were clearly used for two-byte registers and one letter for single byte registers. That might be led by my Z80 experience, as it used that naming scheme. But so might the 6502 designers/datasheet-authors, who would have known of the 8080 which used the same register naming scheme. I remember it described in many places as a 16-bit register with rollover in the low byte and always 01h in the high byte. Either way, we should go with what the datasheet and the instruction set use rather than anyone's recollected opinion, otherwise we're writing conjecture.ToaneeM (talk) 09:19, 9 November 2019 (UTC)

Of course, but the data sheet nowhere says "the stack pointer register is known as S". I listed what it says, and it simply uses S in a couple of places where extreme brevity was required. Johnuniq (talk) 02:31, 10 November 2019 (UTC)

Page 31 of the hardware manual lists the registers and calls it S there as well, without the need for brevity TEDickey (talk) 11:27, 10 November 2019 (UTC)

That sounds conclusive: S it is, of course.ToaneeM (talk) 16:43, 10 November 2019 (UTC)