| ??? 11/26/07 06:54 Read: times |
#147402 - delay Responding to: ???'s previous message |
Richard Erlacher said:
... as one might encounter when combining several blocks of on board RAM to form a deeper, wider one? What's the price one has to pay, in quantative terms? With 4-bit LUT's, it's going to be quite a bit of delay, when one needs a 36-bit-wide RAM buffer, 32K-words deep, isn't it? Enough to warrant considering another solution, maybe? Richard, Before condemning muxes built from simple 4-LUTs as being too slow, it might be worth your while to code your buffer or mux or whatever, then synthesize and implement it, choosing a Spartan 3E as the target. Betcha it'll be "fast enough." In other words, the "another solution" worth considering is a newer device. And those newer devices might be cheaper, too. Besides, 32k words x 36 bits requires 1,179,648 bits. Spartan 2 and 2E have nowhere near that much block RAM, and you're into the very large (and $$$$) XC3S4000 or XC3S5000 or XC3SD1800A devices or bigger Virtex 2/4/5 devices if you want it internal. No Spartan 3, 3E or 3A device has that much block RAM. You're probably better off with an external SRAM. -a |
| Topic | Author | Date |
| Tri-state busses in FPGAs | 01/01/70 00:00 | |
| Tristate Buffers (TBUFs) have been phased out | 01/01/70 00:00 | |
| Thank you | 01/01/70 00:00 | |
| Closing the loop | 01/01/70 00:00 | |
| siumulate? | 01/01/70 00:00 | |
| I didn't simulate it (yet) | 01/01/70 00:00 | |
| hmmm | 01/01/70 00:00 | |
| So ... what about a BIG multi-party bus? | 01/01/70 00:00 | |
| delay | 01/01/70 00:00 | |
| nevertheless ... | 01/01/70 00:00 | |
| re: nevertheless | 01/01/70 00:00 | |
| What disappoints me is the advertising vs reality | 01/01/70 00:00 | |
| advertising | 01/01/70 00:00 | |
| advertising, badvertising ... lies! | 01/01/70 00:00 | |
| oy | 01/01/70 00:00 | |
If only one could rely on them ... | 01/01/70 00:00 | |
| largely, it's because it's not an option | 01/01/70 00:00 | |
| Zackly | 01/01/70 00:00 | |
| If you have internal tristate resources ... | 01/01/70 00:00 | |
| I have new worries now | 01/01/70 00:00 | |
| tristates in FPGAs | 01/01/70 00:00 |