12 Aug
2004
12 Aug
'04
10:49 a.m.
no mention of age and unfortunately I am old enough to have worked on and designed
predicatbale systems...
-----Original Message-----
From: "Dwight K. Elvey" <dwight.elvey(a)amd.com>
Sent: Aug 12, 2004 6:41 PM
To: cctalk(a)classiccmp.org
Subject: Re: Let's develop an open-source media archive standard
Hi
I was more referring to a modern PC than specific
older hardware. The issue with doing direct I/O
is the it needs to be predictable and on time.
Most modern machines can no longer to that reliably
without using DMA. They have too may other things
that they are expected to do simultaneously. Also
because of multiple levels of caching, real-time
predictability is not practical.
In the N*, they dedicate a predictable processor
to do just the disk I/O and nothing else.
Dwight
From: "Steve Thatcher"
<melamy(a)earthlink.net>
I seem to recall that my slow old N* Horizon was doing dd at 4mhz with no dma -
in
fact it was polled I/O because their wait for I/O available kept locking up
so I modified it.
best regards, Steve Thatcher
-----Original Message-----
From: Fred Cisin <cisin(a)xenosoft.com>
Sent: Aug 12, 2004 5:12 PM
To: "General Discussion: On-Topic and Off-Topic Posts"
<cctalk(a)classiccmp.org>
Subject: Re: Let's develop an open-source media archive standard
On Thu, 12 Aug 2004, Dwight K. Elvey wrote:
Hi Jules
Here is what I've found. It is a disk drive emulator.
Unless a PC is DMA driven, bit banging a floppy is not practical.
Disk I/O without DMA is not practical. But it IS possible.
Consider the PCJr and Tandy 1000, both of which do disk I/O
without DMA on 4.77MHz? machines.