🚀 go-pugleaf

In article <1796@cbnewsh.ATT.COM> fdl@cbnewsh.ATT.COM (f.d.la rocca) writes:
>I am trying to gain an understanding of the kind of
>performance Multibus II and VME backplanes actually deliver.
>The claim is that MBII and VME get about 32Mbps.
                                          ^^^^^^
Do you really mean 32 Mega-bits-per-second?
>However, when measured thru-put is quite a bit less
>because of the software overhead in the case of MBII. Not being
>as familiar with VME I don't think software over head is as big and issue
>in that its shared memory vs. message passing.
[stuff deleted]
Well it's been quite a while since I've looked at either of the specs (and
I'm at home right now) (WARNING-possible memory parity error) but it seems
to me that the theoretical max for MBII was about 40 MBytes/sec (one 4-byte
transfer every 100nS) while the theoretical max for VME was about 48 Mbytes-
per-second (one 4-byte transfer every 60 nS).
Neither of them ever (to my knowledge) got that. But both of them, given the
proper memory system, could comfortably run in the 20-30 Mbyte/sec range.
I have personally measured > 100Mbits/sec on a VME backplane. (2 50Mbit/sec
serial channels plus transaction overhead).
I am really out of touch with the NuBUS and FutureBus activity so someone
else will have to provide some guidance there.

Regards,
--
Ron Widell, Field Applications Eng.     |UUCP: {...}mcdchg!motmpl!ron
Motorola Semiconductor Products, Inc.,  |Voice:(612)941-6800
9600 W. 76th St., Suite G               | I'm from Silicon Tundra,
Eden Prairie, Mn. 55344 -3718           | what could I know?