Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!tut.cis.ohio-state.edu!ucbvax!motmpl.UUCP!ron From: ron@motmpl.UUCP (Ron Widell) Newsgroups: comp.protocols.ibm Subject: Re: MBII, VME performance Message-ID: <8907040622.AA19793@jade.berkeley.edu> Date: 3 Jul 89 06:44:23 GMT Sender: daemon@ucbvax.BERKELEY.EDU Reply-To: Ron Widell Organization: The Internet Lines: 29 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?