On 1/6/2010 10:59 PM, Sebastian Kuzminsky wrote: > Dave wrote: > >> On 1/6/2010 4:21 PM, Sebastian Kuzminsky wrote: >> >>> There is currently nothing to be gained by using the 5i23 over the 5i20, >>> but there are two possible future advantages that may become real some >>> time. One is that the 5i23 has a 400 Kgate FPGA (vs the 200 Kgate FPGA >>> on the 5i20), the other is that the 5i23's PCI chipset can support DMA. >>> >>> There are currently no hostmot2 firmwares that don't fit in 200 Kgates, >>> and the EMC2 hostmot2 driver does not currently use DMA. But who knows >>> that 2010 will bring? >>> >> OK Seb, if it was your money and you were going to buy the board set to >> use for the next few years, which one would you buy? :-) >> > I'd get the 5i20. ;-) > > > >> How close is the existing FPGA program to running out of the 200K gate >> space?? >> > Hm... Not sure about this one. All the "pwm+encoder" servos and > steppers you could possibly want fit in 200K. > > I think more room becomes useful mostly if you want to hook up other > kinds of esoteric equipment like SPI and SSI sensors (like ADCs and > resolvers), etc. Or for other firmwares, like SoftDMC, which puts a > dedicated processor on the FPGA in addition to all the HostMot2-like > motion control stuff. > > So, probably 200K is plenty for most folks. > > > >> Does adding DMA make sense? >> > The 5i2* series of cards do fine without DMA since they sit right on the > PCI bus, but the 3x20 would *really* benefit from DMA because it sits > behind an on-board PCIE-to-PCI bridge. > > I'm not sure how much speed improvement the 5i2* boards would get from > DMA, they're pretty freaking fast already... > > > Thanks Seb!
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