Honored ContributorI have a design for speed grade C8. Now purchase would like to buy chips with speed grade C7.
Will the binary that was build for speed grade C8 function properly in a chip with speed grade C7 ? Can I tell QuartusII that the binary will be downloaded to multiple speed grades, something like migration devices ? Thank's ! / Henrik
Honored ContributorIt will run but you should repeat the timing analysis for the slower device and ensure that you image meets timing for the C7 device.
Honored Contributora C7 is faster than a C8
you can add both devices to your design as migration menue -> Assignments -> Device -> Migration Devices here you can add the C7 and the C8 device of course you need to recompile this option is also usefull when you plan to place different devices with the same footprint like EP2C35F484 and EP2C50F484 as an asssembly option, so the pin planer and other functions know about the migration and help you "not" to choose for example IOs that are not IOs on different parts.Honored ContributorYou don't need to recompile as long as you performed multi-corder timing analysis. Which you should always do anyway, because there is no guarantee that a specific chip marked as C8 isn't really a C7 one. Speed grades are guaranted in one direction only, for being "not slower than...".
Honored Contributorif you actually add migration devices you have changed the .qsf and you may need to recompile. however, the existing compilation database can be re-timed using the faster speed grade without going through a full compile
Honored ContributorThank you all for your replies!
I added speed grades C7 C6 and I7 as migration devices and using C8 as base device, and got the following warning: Warning: Devices selected for migration have different speed grades -- frequency limits are checked only for current device, not all devices Does this mean that timing analyses as only been done for C8 or is it only Fmax that apply for C8 ? /HenrikHonored Contributorsounds like its saying TimeQuest will only do a timing analysis for the currently selected C8 speed grade, not all of the speed grades in the migration devices
Honored ContributorPlease read my previous post. Do not add any migration devices. There is no need to do that, and it is not the correct way. All you have to do is to make sure that multi corner static timing analysis is being performed. Depending on your device and Quartus version, this is the default anyway, so you might not need to do anything but just checking.
Multi-corner TA means that, at least, the fast model is used as well (besides the slow one). The fast model, besides considering best case voltage and temperature, it also consider best case silicon process, which is exactly the fastest speed grade. This is regardless of the speed grade of the selected device. Fast model timing is the same for all speed grades. And once again, the reason is that there is no guarantee that a specific part isn't faster than the specs. The only guarantee by the manufacturer, is that it is not slower than the marked speed grade. In other words, you can purchase C8 parts and they might perform as C7 ones. Bottom line. Perform multi-corner timing analysis. And not just in this case, but always.Honored ContributorHi,
Given a given quartus_fit result, you can re-run TimeQuest for multiple speed grades by using the --speed command-line argument. In your case, you can just re-run the analysis for the "7" speed grade: quartus_sta mydesign --speed 7 Using the GUI, you will need to manually open the "Create Timing Netlist..." dialog box ("Netlist" menu) and use the "Speed" drop down to select "7". Hope this helps.Honored ContributorOk, thanks again.
I go for the multi corner analysis strategy. It sound reasonable and simple. :-)
