RE: [Discuss-gnuradio] FPGA / new rx_buffer_inband

[Eric Schneider]

> -----Original Message-----
> From: Brian Padalino [mailto:address@hidden
> Sent: Sunday, September 07, 2008 7:21 AM
> 
> Were these results for the 2 channel mode?
> 
> What is the size difference within the USRP when using 2 channels?  Is
> it significant or pretty insignificant?

They were from the 1 channel build.

Here is a snippet from inband_2rxhb_2tx.rbf:

ch: 0   s: 965745       delta: 8064
ch: 1   s: 965745       delta: 8064
ch: 0   s: 973809       delta: 8064
ch: 1   s: 973809       delta: 8064
ch: 0   s: 981873       delta: 8064
ch: 1   s: 981873       delta: 8064
ch: 0   s: 989937       delta: 8064
ch: 1   s: 989937       delta: 8064
ch: 0   s: 998001       delta: 8064
ch: 1   s: 998001       delta: 8064

The channels seem well aligned at least.

Unfortunately, I am getting regular segfaults on 2rx...  :-/

Resource Comparison:

New 2 chan:
; Compilation Hierarchy Node                                 ; Logic Cells ;
LC Registers ; Memory Bits ; M4Ks
;    |rx_buffer_inband:rx_buffer|                            ; 983 (59)    ;
697          ; 72576       ; 18
;       |packet_builder:pb|                                  ; 162 (162)   ;
19           ; 0           ; 0
;       |rx_channel_buffer:cb[0].chan_buf[0]|                ; 249 (68)    ;
209          ; 24192       ; 6


Orig 2 chan:
; Compilation Hierarchy Node                                 ; Logic Cells ;
LC Registers ; Memory Bits ; M4Ks  
;    |rx_buffer_inband:rx_buffer|                            ; 546 (119)   ;
318          ; 114688      ; 28 
;       |packet_builder:rx_pkt_builer|                       ; 137 (137)   ;
41           ; 0           ; 0
;       |fifo_1kx16:generate_channel_fifos[0].rx_chan_fifo|  ; 43 (0)      ;
33           ; 16384       ; 4  
;       |fifo_4kx16_dc:rx_usb_fifo|                          ; 158 (0)     ;
134          ; 65536       ; 16


I haven't done any optimization yet, so I'm not sure how much the logic cell
utilization could be reduced.  I imagine a fair amount of it comes from my
use of 64 bit wide data paths for header data.  I may try a hybrid version
where the header data is muxed into a 16b header fifo.  There shouldn't be
any performance penalty except for very short packets (< 64 bytes, e.g.
command channel).  The header fifo capacity would be better utilized then as
well.

The new code has 4+2 M4Ks (vs just 4) per channel, but with no usb_fifo (+16
M4K), so memory comparison is not really apples to apples.  We could split
the usb_fifo memory between the channels and give each 2-4k per channel.

--ets