Hello everyone!
My name is Vladimir. Sorry for my english, but 'as is'...
My job is not related to computers and IT, this is something like a hobby.
I have some small experience with 8080 and Z80. Recently, the 6502 kingdom attracts me increasingly and I started to get everything related to 6502.
But, closer to the point. I got hold a 65c22 chip, but neither datasheet nor chip marking can help me to figure out the frequency range of device.
The marking appears as follows:

R65C22P
11450-12
MEXICO
1423 B55534-2

What does it mean?
Thanks.

Welcome.

Strange. I've never seen them without a numeral after the "P" to tell the number of MHz, for example R65C22P4.

_________________
http://WilsonMinesCo.com/ lots of 6502 resources
The "second front page" is http://wilsonminesco.com/links.html .
What's an additional VIA among friends, anyhow?

There is an inscription on the back side (bottom) too:

748 K494R
3013A1000
MEXICO R

Isn't that designation used for 1-MHz parts like the R6522P pictured below?

My old dinosaur brain seems to be telling me that the absence of a speed designator means it's a 1 MHz part.

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x86?  We ain't got no x86.  We don't NEED no stinking x86!

To Michael: Maybe. But, how did you know that it is 1 MHz? Your marking tells me nothing...

IIRC the first versions of the parts were all 1MHz. So no special speed designation was necessary. When the faster parts became available it became necessary to add the number, e.g. P2, P4 etc. And 1MHz parts produced after that point would be P1. You'll sometimes see the same thing happening in various other fields, not just for chips.

Maybe, firstly no special speed designation was nesessary. And finally, improving technologies should lead to the same situation, no need for designators. Say, sorting chips based on their operating speed performance results success rate 99 percent, all the chips are 4 MHz or faster. Is this possible? Notice, the date of my chips is 1423.
2014, two years ago.

I think it's a P1 part and the digit has wrapped round to the next line where it's followed by the date code for the packaging process (1450) which is was around six months after the silicon was made (1423).

The logo limits the length of the first three text lines. Look at the 6522 photo.

_________________
Andrew Jacobs
6502 & PIC Stuff - http://www.obelisk.me.uk/
Cross-Platform 6502/65C02/65816 Macro Assembler - http://www.obelisk.me.uk/dev65/
Open Source Projects - https://github.com/andrew-jacobs

I have no other 65c22 for comparison, but there is four R65C51P2.
An analysis of their marking does not confirm your guess.
The marking is as follows:

1-st:
R65C51P2
11470-14
MEXICO
9237 A23618-4

2-nd:
R65C51P2
11470-14
MEXICO
9415 A37995-3

3-rd:
R65C51P2
11470-14
MEXICO
9525 S10102-2

4-th:
R65C51P2
11470-14
PHILIPPINES
9649 B25846.2

The line 11470-14 is an essential own of this chip. This is not a date.
Apparently , it is necessary to perform an experiment, to test frequency characteristics of my 65C22.