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Melkhior | _florent_: in the DDR3 gist you posted, the code assumes you already know the timings needed if I understand correctly ? bitslip and delay are hard-coded | 06:25 |
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_florent_ | Melkhior: yes exactly, I was using fixed bitslip/delays (the one knowing to work with the BIOS) | 06:58 |
_florent_ | we have enough margin to have something usable | 06:59 |
Melkhior | _florent_: would that work per-design ? I.e. if you calibrate on a specific board, would that still work on a different board of the same make and model ? | 07:00 |
_florent_ | and that's also used by some vendors | 07:00 |
_florent_ | Melkhior: the variation between boards should be negligeable vs the margin we have, so once calibrated on a board, it should work on other similar boards (On Digilent Arty it was the case) | 07:03 |
Melkhior | OK thanks | 07:03 |
Melkhior | Just writing values if Forth should be much easier than trying to implement all the testing loops... | 07:03 |
Melkhior | Although nothing is going to use the SDRAM before the OS has booted on the host anyway :-) | 07:04 |
Melkhior | Swapping to the FPGA DDR3 controller by litedram with a custom DMA talking to LiteDRAM{Reader,Writer} is a lot faster than swapping to a micro-sd card on a SCSI2SD V6 behing the ESP SCSI controller! | 07:06 |
Melkhior | Glad I switched from my home-grown VHDL to a Litex SoC and Migen :-) | 07:07 |
Melkhior | thanks again !!! | 07:07 |
_florent_ | Melkhior: I think I had also had a simple python script to do the DDR3 calibration and find the bitslip/delays over UARTBone, I'll try to find it | 08:16 |
_florent_ | Melkhior: found it, I added it to the gist: https://gist.github.com/enjoy-digital/529a4d9994f0cc95e45382e4eb253b09#file-test_sdram_init-py | 08:22 |
Melkhior | thx | 08:23 |
_florent_ | So I was using this script to find the bitslip/delays values to use with the SDRAMInit module on Arty | 08:23 |
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leons | Can I expect any persistent damage to my Xilinx Kintex7 FPGA if I choose the wrong speedgrade while building the bitstream? | 12:28 |
gatecat | nope | 12:28 |
gatecat | if you chose a speedgrade lower than the actual one, then there won't be a problem at all | 12:29 |
gatecat | if you choose one higher than the actual one, there's a possibility at worst the design won't work or will be unreliable | 12:29 |
leons | lower, meaning slower, meaning higher number? I don't really get Xilinx's logic there... | 12:29 |
gatecat | a lower speedgrade is slower in Xilinx land | 12:30 |
gatecat | yes this is the opposite to DRAM etc | 12:30 |
leons | Ah, okay. I thought I ready somewhere lower number = faster, but that's good to know | 12:30 |
gatecat | I think that might be in Intel land | 12:31 |
gatecat | both Lattice and Xilinx have speedgrade being lower=slower | 12:31 |
leons | I'm trying to prepare a patch to port LiteX to some FPGA board where the documentation does not mention the speedgrade anywhere | 12:31 |
leons | So I've been just using -1, given I didn't have physical access to the FPGA | 12:32 |
gatecat | yeah, that's fair | 12:32 |
leons | And I was wondering whether different production runs of the board might have a different speedgrade | 12:32 |
leons | Oh, now I'm really confused: xc7k325tffg676-1, is that Speedgrade "1" or "-1"? In the sense would "-2" be a higher or lower number? :D | 12:33 |
leons | As in: is it a signed integer? :) | 12:34 |
gatecat | no, it's not signed | 12:34 |
gatecat | the dash is a separator not a minus | 12:34 |
leons | Ah, okay, thanks for clarifying! | 12:35 |
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