MCF52259 -- errata? Address fetch speculation?

[RichTestardi]

Hi all,

I noticed in the 52259 stationery that flash address speculation is still disabled in FLASHBAR bit 6.

However, I was unable to find any errata that might indicate this is broken, like in the 52221 or 52233.

Does anyone know if it is safe to turn it on?

It sure seems to work, and gives an instant 9% performance improvement for my application, on top of the 5% that seems intrinsic in the 52259 already!

(With it turned on, 52221's and 52233's can't even boot my application.)

-- Rich

[mjbcswitzerland · Accepted solution]

Hi Rich

I received confirmation from freescale that the "speculaton bug has been fixed in the MCF5225X". This means that the workaround is no longer needed for this chip.

Regards

Mark

www.uTasker.com

[RichTestardi]

Awesome, thanks!!!

We broke 100,000 StickOS BASIC statements per second on the MCF52259! :smileyhappy:

-- Rich

[Nouchi]

Hi Rich,

If the AFS bit still in the Reference Manual, I guess it works, because there's no AFS anymore in the MCF52235RM/MCR52223RM (bit 7-6 reserved, should be cleared).  This feature seems to be discarded on kirin2 devices. I don't seen any kirin3 device errata for the moment.


Emmanuel

[RichTestardi]

I'm not really sure the absence in the 52223/52235 reference manual means anything, since both the 52223 and 52235 errata's say:

Use FLASHBAR[6] to enable or disable the address speculation mechanisms of the flash controller. The default configuration (FLASHBAR[6] = 0) enables the address speculation. If FLASHBAR[6] equals 1, address speculation is disabled. Core performance may be degraded from 4% – 9%, depending heavily on application code.

So you actually have to *set* a reserved bit in this case, and the stationery startup code does just that.