Path: utzoo!utgpu!watmath!isishq!f171.n221.z1.FIDONET.ORG!izot
From: izot@f171.n221.z1.FIDONET.ORG (Geoffrey Welsh)
Newsgroups: comp.sys.cbm
Subject: Re: SEQ file access speedup
Message-ID: <1606.23F8D15A@isishq.FIDONET.ORG>
Date: 14 Feb 89 14:30:32 GMT
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 > From: jgreco@csd4.milw.wisc.edu (Joe Greco)
 > Message-ID: <955@csd4.milw.wisc.edu>
 > Device(s)               Time    Filesize CPS    %speed
 > ----------------------- ------- -------- ------ ------
 > Regular 1541/C64        01:35.2    33453    351    100
 > C64/BusCard II/8050     00:31.8    30234    952    271
 > C64/Custom MSD/8050     00:17.3    30234   1745    497
 > C64/RAMDOS 3.2/1750     00:12.2    38760   3188    908
 
   Add to the list (result from my memory):
 
   C128/C64-Link II/SFD                       1900
   HyperPET/D9060                             Bloody fast - I'll get specs!
 
   The C128 was running at 2 MHz.
 
   The "HyperPET" is a 4 MHz 4032.
 
 > As a side note:  The way my memory recalls, the IEEE bus is actually
 > capable of megabyte/second rates.  Of course, my magnetic media is
 > probably flaking again....
 
   The IEEE-488-1979 spec says that the data transfer rate shall not exceed 1 
megabyte per second, but the handshake is designed to slow the transfers down 
to the slowest selected device on the bus. Since it takes several 1 MHz clock 
cycles to program the I/O chips to send the handshake signals, megabyte per 
second speeds are way out of the question.
 
   There is also the question of how quickly the data can be "lifted" from the 
disk. Even with most IEEE drives' 2-processor design, there is a severe limit 
to the speed with which the data can be put on the bus.
 
   Nevertheless, some sort of automated hardware handshake and more tightly 
coded ROMs in the drive would lead to vastly improved performance.
 
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