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diff --git a/share/examples/atm/NOTES b/share/examples/atm/NOTES deleted file mode 100644 index aad4190..0000000 --- a/share/examples/atm/NOTES +++ /dev/null @@ -1,54 +0,0 @@ - - HARP Notes - 1998-09-14 - -This is a list of currently known incompatibilities and miscellaneous gotchas -in HARP. - -To report new items, please send mail to harp-bugs@magic.net. - -================================================================================ - - -Efficient Driver and DMA sizes -============================== - -The Efficient adapter moves PDUs between host memory and adapter memory with -the help of DMA descriptor lists. Each DMA descriptor consists of two words. -Word 0 contains a DMA type identifier and a repetition count. Word 1 contains -the physical (not virtual) host buffer address. Each DMA type is really an -encoding of the burst size for the DMA. (See /usr/src/sys/dev/hea/eni.h for -more on the DMA types.) HARP was originally developed using burst sizes of -8_WORD, 4_WORD, and 1_WORD sizes. Each DMA request would be built to first -move as much data as possible using an 8_WORD burst. This should leave 0-7 -words left over. If there were more than 3 words remaining, a 4_WORD DMA burst -would be scheduled. The remaining data must then be 0-3 words in length and -would be moved with 1_WORD bursts. The use of large burst sizes makes more -efficient use of DMA by performing the same amount of work in fewer cycles. - -Several users have reported problems with DMA which were characterized by error -messages of the form: - - "eni_output: Transmit drain queue is full. Resources will be lost." -or - "eni_output: not enough room in DMA queue". - -It was determined that these systems do not support the use of four- or -eight-word DMA bursts. To resolve this problem, HARP now #ifdef's around the -8_WORD and 4_WORD DMA setup and #undef's both values by default. This results -in the default operation of the Efficient driver to use only 1_WORD DMA bursts. - -If you wish to experiment with larger DMA bursts, you can edit the file -/usr/src/sys/dev/hea/eni_transmit.c and change the #undef to a #define for -DMA_USE_8WORD and/or DMA_USE_4WORD. You will need to rebuild and install your -kernel for this change to take effect. - -We are exploring solutions which would allow HARP to determine which DMA bursts -are supported by the system at run-time. This would allow the Efficient device -driver to make use of larger, more efficient burst sizes where supported -without halting on systems which can't support the larger sizes. - - - - @(#) $FreeBSD$ - |
