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From: stripes@pix.com (Josh Osborne)
Subject: Re: ISA is faster than EISA ? (Was: Re: DOS and 386BSD (and NT and OS2))
Message-ID: <BwLn48.Cu4@pix.com>
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Organization: Pix Technologies -- The company with no adult supervision
References: <1992Oct22.093459.13824@autelca.ascom.ch> <BwIwu4.Mx6@pix.com> <1992Oct23.140133.29341@microware.com>
Date: Sat, 24 Oct 1992 00:09:43 GMT
Lines: 57
In article <1992Oct23.140133.29341@microware.com> adam@microware.com (Adam Goldberg) writes:
[...]
>>You would be lucky to find a disk that did more then 1M/second.
>>Of corse, since the video is also on that bus, and video tends to suck
>>tons of bandwidth, having an EISA bus may make your disks seem faster
>>because there is more bandwidth to share...
>
>My system:
> Adaptec 1540
> Quantum LPS-series HD (210MB, or so)
> 386-25, 64k cache (Gateway)
> OS-9000 operating system
> ISA Bus.
>
>My results:
>
>(Calvin)/h0/USR/ADAM:timeio -r -b=200k -f=/h0@ -n=10
>Timing how long it takes to read /h0@ (204800 bytes)
[...]
>9:45:33 - 9:45:33 (0.16 seconds), 1280000 bytes/second
[...]
>9:45:34 - 9:45:34 (0.12 seconds), 1706666 bytes/second
[...]
>For an average of 1.76MB/second.
I really should have said 2M a second, still, your drive may well not be this
fast. First off, 200K is likely to be far below the size of the buffer cache
in your system, does timeio bypass the OS's cache? Even if it does, read on...
>Once upon a time, I hooked the same drive up to a Compaq 486/33M (EISA)
>with an Adaptec 1740 and got transfer rates in the neighborhood of
>7 MB/second.
Your drive is not this fast.
Many drives come with cache on them (the 1.2G Fujitsu disk comes with 256K or
512K of cache, forget which), I'll bet either your drive has one, or for some
reason the 1740 caches for it (i would doubt a SCSI controler would 'tho).
>You don't need to buy a house for high transfer--you need an OS which
>allows synchronous SCSI transfers.
You don't need to buy a house, you need to buy an expensiave disk, I don't
know if it really costs $200k, but it is more then $1 to $2k.
Your drive can't read data faster then it spins under the read heads, which
is normally 3000RPM, but 4500RPM is getting popular. Make that sectors/track
times RPM divided by 1 min times the data/sector. Yeah, that's it. Well,
assuming only one head can read at once (not allways true). That's a max.
When you benchmark a disk, use a BIG file, twice your RAM size is good.
--
stripes@pix.com "Security for Unix is like
Josh_Osborne@Real_World,The Multitasking for MS-DOS"
"The dyslexic porgramer" - Kevin Lockwood
We all agree on the necessity of compromise. We just can't agree on
when it's necessary to compromise. - Larry Wall