Post Reply 
HP 48GX cpu clock speed
02-26-2020, 07:21 PM
Post: #1
HP 48GX cpu clock speed
I just picked up a second HP 48GX, 2002 manufacture, and was interested to note a different cpu clock speed — as shown by A in the On-D self-tests — compared to my other one (same year).

One is 3.7MHz (roughly), and one is 3.9MHz; by coincidence, both serial numbers indicate week 37 of 2002.

Is that surprising? The wikipedia article suggests that one might expect 3.9 MHz, for GX, especially later models like mine.

Or is it not that simple?

One difference is that the 3.9MHz one has two RAM cards installed, but I doubt that's relevant.

Obviously, I don't expect to notice any difference in practice, and I could consider SpeedUI were I bothered about the 48 speed anyway, so this is just out of interest Smile

thanks!

Cambridge, UK
41CL/DM41X 12/15C/16C DM15/16 71B 17B/BII/bII+ 28S 42S/DM42 48GX 50g 35s 30b/WP34S Prime G2
& Casios, Rockwell 18R :)
Find all posts by this user
Quote this message in a reply
02-26-2020, 07:35 PM
Post: #2
RE: HP 48GX cpu clock speed
I think this article is a pretty good explanation: https://www.hpcalc.org/hp48/docs/humor/speeed.txt
Visit this user's website Find all posts by this user
Quote this message in a reply
02-26-2020, 07:42 PM
Post: #3
RE: HP 48GX cpu clock speed
ah yes, indeed Smile

Cambridge, UK
41CL/DM41X 12/15C/16C DM15/16 71B 17B/BII/bII+ 28S 42S/DM42 48GX 50g 35s 30b/WP34S Prime G2
& Casios, Rockwell 18R :)
Find all posts by this user
Quote this message in a reply
02-26-2020, 07:50 PM
Post: #4
RE: HP 48GX cpu clock speed
There are some interesting comments here, but the answer isn't clear.

Cambridge, UK
41CL/DM41X 12/15C/16C DM15/16 71B 17B/BII/bII+ 28S 42S/DM42 48GX 50g 35s 30b/WP34S Prime G2
& Casios, Rockwell 18R :)
Find all posts by this user
Quote this message in a reply
02-27-2020, 08:29 AM
Post: #5
RE: HP 48GX cpu clock speed
Hello,

The 48G chips uses an internal oscillator to generate the internal ~4mhz clock...
This oscillator is not tuned at the factory and, due to large variation in silicon wafers will be different from calculator to calculator. It will also change with temperatures as the physical characteristics of the oscillators component (resistors, NOT gates and capacitor) do vary with these...

Modern CPU uses PLL (Phase Locked Loop), which act as precise multiplicators of a precise cristal to set up clocks, but these are much more complex than a simple 2 NOT gate/1 resistor/1 cap system. Which is what the 48 uses.


[Image: WorlB.png]
Cyrille

Although I work for the HP calculator group, the views and opinions I post here are my own. I do not speak for HP.
Find all posts by this user
Quote this message in a reply
02-27-2020, 04:56 PM
Post: #6
RE: HP 48GX cpu clock speed
thanks Cyrille!

Cambridge, UK
41CL/DM41X 12/15C/16C DM15/16 71B 17B/BII/bII+ 28S 42S/DM42 48GX 50g 35s 30b/WP34S Prime G2
& Casios, Rockwell 18R :)
Find all posts by this user
Quote this message in a reply
02-27-2020, 05:40 PM
Post: #7
RE: HP 48GX cpu clock speed
Cyrille:

Thank you - good information.

Is this clock available external to the processor? IE could we pipe in an external clock?
Or perhaps another method to control this clock external to the processor?

Regards,,
TomC

(02-27-2020 08:29 AM)cyrille de brébisson Wrote:  Hello,

The 48G chips uses an internal oscillator to generate the internal ~4mhz clock...
This oscillator is not tuned at the factory and, due to large variation in silicon wafers will be different from calculator to calculator. It will also change with temperatures as the physical characteristics of the oscillators component (resistors, NOT gates and capacitor) do vary with these...

Modern CPU uses PLL (Phase Locked Loop), which act as precise multiplicators of a precise cristal to set up clocks, but these are much more complex than a simple 2 NOT gate/1 resistor/1 cap system. Which is what the 48 uses.


[Image: WorlB.png]
Cyrille
Find all posts by this user
Quote this message in a reply
02-28-2020, 07:20 AM
Post: #8
RE: HP 48GX cpu clock speed
Hello,

From memory, the capacitor is external, but I am only about 75% sure of that...
So, you could theoriticaly try to speed up a calc...

Cyrille

Although I work for the HP calculator group, the views and opinions I post here are my own. I do not speak for HP.
Find all posts by this user
Quote this message in a reply
Post Reply 




User(s) browsing this thread: 1 Guest(s)