lm@slovax.Sun.COM (Larry McVoy) (10/04/90)
In article <18560@rpp386.cactus.org> jfh@rpp386.cactus.org (John F. Haugh II) writes: >In article <143190@sun.Eng.Sun.COM> lm@slovax.Sun.COM (Larry McVoy) writes: >>In article <6167@titcce.cc.titech.ac.jp> mohta@necom830.cc.titech.ac.jp (Masataka Ohta) writes: >>>If you use elaborated and complicated memory disk, it can be only as >>>slow as ordinary disk, but not faster. >> >>Bullsh*t. Tmpfs is orders of magnitude faster than a disk. > >I suspect this was a typo - if tmpfs can only be as slow, and not >any faster, then it must be the same speed. I'm not sure if you think he made the typo or I did, but my statement stands. Just for grins (mydd is a little program that moves I/O like dd but has some other options and timing info stuck in for free): $ mydd if=internal of=/tmp/XXX count=500 fsync=1 4000.00 Kbytes in 0.258 seconds (15505.4 Kbytes/s) $ mydd if=internal of=/usr/tmp/XXX count=500 fsync=1 4000.00 Kbytes in 5.1 seconds (784.386 Kbytes/s) Yeah, so I lied, it's 15MB / sec not 5MB / sec. I was being conservative :-) Actually, slovax is a 4/470 which has bcopy hardware support, the 5MB/sec number is pretty close for a 20MHZ SS1. >As for 5MB/sec transfer limitations - does the SS1 have a DMA >setup that can handle memory to memory transfers? I would hope >that the memory subsystem can handle more than 5MB/sec ... Not by much. A SS1 can't bcopy the data much faster than that. --- Larry McVoy, Sun Microsystems (415) 336-7627 ...!sun!lm or lm@sun.com