Need buying advice for 386 and Unix

[John C. Archambeau]

james at bigtex.cactus.org (James Van Artsdalen) writes:
>In <5682 at crash.cts.com>, jca at pnet01.cts.com (John C. Archambeau) wrote:
>I disagree here.  The data coming off of the hard disk is much less
>than the bandwidth of the AT bus.  Therefore you can't win with just
>an EISA hard disk controller.  What you CAN win with is a caching
>controller, or a controller that can do DMA & has a unix driver that
>can use it, or some other optimization not related to the bus
>bandwidth.  Caching helps ISA too.
>
>It's no accident that the EISA hard disk controllers that are
>appearing have better hardware support (DMA, cache) than their ISA
>counterparts: they wouldn't be much faster if they didn't (note: DMA
>is slower on ISA anyway).
>
>Also note that the fastest EISA Ethernet cards are maybe 5% faster
>than the 8-bit WD-8003.  20Mbytes/sec bus bandwidth isn't needed to
>communicate over a 10Mbit wire.

The reason for wanting EISA specific cards is because of the bus mastering
capabilities.  Admittedly the throughput isn't much, but I'd rather have all
bus mastering cards on a bus that can handle bus mastering cards.  Makes
sense.  If I pay for a bus mastering bus, I certainly want bus mastering
cards.  This goes for EISA or MCA.

>I will be buying EISA stuff for bigtex, but for the caching and DMA
>features.
>
>| (3) get Toshiba SIMMs.
>
>> Why Toshiba?  Memory is memory.  NEC, TI, et. al.
>
>No.  Completely wrong.  Look at a DRAM specification sheet some day.
>There are at least twenty different parameters that must be met.  They
>are are a little different for each SIMM that plugs into the same
>socket.  Part of the design effort in a system is to allow as many
>different SIMMs to be used as possible, and then make sure you *don't*
>ship the ones that won't work.  RAS precharge time & friends: all that
>fun stuff.

I have yet to find a memory module that you can't plug in.  Whether it be a
Mac, Sun, 286, or 386 box.  If you buy chips from places such as the Chip
Merchant, you are subject to what they have in stock.

Admittedly, some memory modules work better than others.  My 386SX motherboard
manual lists a long list of memory that has been tested to work by
manufacturer and their part number.

But the chances of pulling a particular DRAM chip off the shelf and having it
work are VERY high if it's a well designed board.  Remember the memory chip
shortage not to long ago?  A lot of chip vendors just plain weren't selling in
the USA, so you took what you could get.
 
     // JCA

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