Overclocking PIC16F877A - why not ;)

[rfmw]

overclock avr atmega128

With a DDS 1-40MHz generator with TTL/CMOS outputs I tried to overclock a PIC16F877A (with no frequency marking - so it a 20 MHz version).

To be sure that the PIC is still fully functional at higher frequencies, I wrote the program so that it was computing a multiplication with 32-bit floating numbers and displaying the result at 2x16 LCD (LM016 clone).

Guess what, at 35 MHz PIC worked beautifully, while at 36-37 MHz it started to show incorrect results/glitches, finally at 38 MHz it freezed.

From 20MHz -> 35 MHz is 75% increase in computational speed giving 8.75 MIPS. Not bad at all

 

[asit]

pic16f877a overclocking

has anybody overclocked AVR?

 

[pisoiu]

overclocking a pic

Generally, the maximum clocking freq. can be increased, and up to a certain limit, the uC will work. But these tests are made at home, in a fixed temperature environment, with a fixed value power supply. Put the uC at a higher freq. than described in datasheet, and play around with power supply voltage over entire functional range, with the temperature over the entire range, and with loads in ports. I am sure you'll find a lot of combination of these variables where the CPU will not work.

/pisoiu

 

[rfmw]

16f84 38mhz

I forgot to mention before that I've seen people running their PIC16F84-04 at 24 MHz 8O , no kidding.

 

[Sobakava]

pic16f877a security bits

I tried PIC18F452 (40MHz normal speed) recently... some of them could work up to 48MHz but became very sensitive to external factors...(I mean noise,temperature etc)

 

[tgq]

ubicom ip3xxx

I forgot to mention before that I've seen people running their PIC16F84-04 at 24 MHz 8O , no kidding.

I think it was 16F84A-04
16F84A-04 and 16F84A-20 seem to be exactly the same chips, the print on package = the only difference :lol:

 

[hill]

overclocking pic16f

Generally, over-clocking a micro-controller is a bad idea. It sounds like fixing a pair of turbo engine at the back of your car and drive it.

 

[eltonjohn]

pic16f877a overclock

When a MANUFACTURER rates the FREQUENCY of a CPU .That doesn't means that this is the LIMIT frequency that the CPU can run . It means that is safe to OPERATE it UP to that FREQUENCY and in a well known temperature ENVIROMENT (COMERCIAL ,MILITARY or AUTOMOBIL). ! What do you gain put it out a PRODUCT with a OVER STRESSED and NOT RELIABLE component . Only trouble and the END of your COMPANY !
Young PEOPLE do this on PC'S but at least in those boxes you have the possibility of GOOD COOLING SYSTEM .. Most CPU rated at a particular frequency have could run between 10% and 20% faster than rated Frequency .But this is a "Shady" area where impredictable things could occur .And they do occur .Also is another very commun practice in the industry is to use the SAME PRODUCT but rated in diferent frequencies . Of course the real frequency is the higher one .This is done to CUT DOWN manufacturing COSTS . instead of making 2 or 3 products .They only make one and sell it at different prices . Ok i hope this help to see that in this AREA you don't gain NOTHING .. but a SHADY AREA of INCERTAINTY .
What is next . OPERATE TTL logic at 4V ... or at 6 V?

 

[tgq]

pic18 overclocking damage

Also is another very commun practice in the industry is to use the SAME PRODUCT but rated in diferent frequencies . Of course the real frequency is the higher one .This is done to CUT DOWN manufacturing COSTS . instead of making 2 or 3 products .They only make one and sell it at different prices . Ok i hope this help to see that in this AREA you don't gain NOTHING .. but a SHADY AREA of INCERTAINTY .

yes Microchip do this with its products :wink:

 

[surachai]

pic mcu overclocking

I used 16f876a with x'tal 22.118MHz, It's work stability.

 

[SphinX]

Salam,

I have used PIC16F84-04 with 8MHz crystal

Bye

 

[C-Man]

Salam,

I have used PIC16F84-04 with 8MHz crystal

Bye

I also used a few thousand of 16F84-04 with 8MHz they are all still working after about 3 years under this condition, not even one has failed

But this does not mean that other Microchip controllers can also operate soo far out of their specs ...

best regards

 

[tgq]

[But this does not mean that other Microchip controllers can also operate soo far out of their specs ...

yes this is not technical but marketing considerations
what a secret :lol:

 

[mucko]

Some modules may not work properly when overclocked

 

[tgq]

The Microchip rule is : limited speed device has the same speed than the fastest device in the same category
example 16F84-04 and 16F84-10 are the same chip :wink:
16F84A-04 and 16F84A-20 are the same chip :wink:
real overclocking 16F84A @ 25MHz is another problem, reliability :?:

 

[mmengi]

16F84A 04/P working properly at 10 Mhz.

 

[ME]

has anybody overclocked AVR?

I have seen 16MHz AVRs overclocked at 24MHz:

The newest AVRs like ATmega48/88/168 and ATtiny13/2313 are specified to run up to 20MHz, so they can probably be overclocked even more.

Remember that AVR doesn't divide the clock speed by 4 internal, like PIC does. AVR has a 1:1 ratio vs. PIC 1:4 ratio. But new PIC18's can run at either up 40MHz, with 1:4 division or use a 10MHz crystal with internal PLL to run with 1:1 ratio, but only up to 10MHz if you don't overclock it.

Other fast 8-bit Microcontrollers than AVR is the pipelined 8051 microcontrolles from Dallas/Maxim and from Silicon Laboratories (fromer Cygnal).
Silicon Laboratories has 8051's specified to run up to 100MHz.


PIC's are slower than both AVR's and these fast 8051's, but if you want a fast PIC, then you should check out the Ubicom SX PIC clones.
The cheapest fast performing 8-bit MCU is probably AVR, it's in the same price range as PIC but much faster.

Maybe there are some fast performing Japanese/Asian 8-bit MCU's, I'm not so familiar with them. Try to check out www.renesas.com (former Hitachi an Mitsubishi), they have some very popular microcontrollers too, like the H8 family etc.
But for hobby use, it's usally easier to get access to AVR, PIC, 68HCxx, Zilog and various 8051's in Europe and America; probably because all of these MCU's are made by European and American IC vendors.

You could also use 16-bit MCUs like MSP430 etc. or the 16/32-bit ARM7 or if you need more speed.
Atmel has just introduced the first ARM7 MCUs below $3.
Philips also makes the very popular and cheap LPC2000 ARM7 MCUs.

 

[Sputnik]

I've come across a web site that took a PIC (I can't remember which one, but I think it was the 16F84, my favourite!) and overclocked it to 32 MHz while maintaining a serial communication link to a computer. But then again the 16F84 doesn't have a serial port so I don't know which chip it was, oh well, at least it can be done.

Sputnik

 

[ME]

Try to read this press release from Atmel:
http://www.atmel.com/dyn/corporate/...eName=AT91SAM7S32_10_19.html&SEC_NAME=Product

Atmel Introduces World's First Sub $3 ARM7 Flash Microcontroller

Targeted at 8-bit designs with in-system programmable Flash, single supply operation, BOD, POR, RC Oscillator, HW security bit and USB device


These cheap "industry-standard" 32-bit microcontrollers will probably challange not only the 16-bit microcontrollers, but also the high performing high-pin count 8-bit microcontrollers like their own ATmega AVR's.

 

[davorin]

Another idea is to synthesize your own PIC into FPGA..though loosing all the cool analog periphals...

At least you reach 120 - 150MHz clock easily (o;