Path: utzoo!attcan!utgpu!jarvis.csri.toronto.edu!mailrus!cs.utexas.edu!uunet!portal!cup.portal.com!cliffhanger
From: cliffhanger@cup.portal.com (Cliff C Heyer)
Newsgroups: comp.unix.i386
Subject: "Real" speed of AT bus (MB/sec)?
Message-ID: <22080@cup.portal.com>
Date: 12 Sep 89 02:41:21 GMT
Organization: The Portal System (TM)
Lines: 24


I'm having difficulty getting
the specifications of the AT bus
strait.

What is the speed of the AT bus
in MBytes/sec? (Thats 
millions of 8-bit bytes per second).

I know it's rated at 8MHz, but does
that mean 8 bits are transferred in
parallel with each cycle, or 16 bits
with each cycle, or is the transfer
serial at 8 Mbits/sec?

Is I/O done in blocks so that, for 
example, 512 bytes can be transferred
via one I/O instruction, and the CPU
can go on to do other work while the
transfer takes place? (DMA) Or does
the CPU have to issue a memory write
instruction for each byte?

Please POST your answers.