Path: utzoo!utgpu!cunews!bnrgate!bwdls58!mlord
From: mlord@bwdls58.bnr.ca (Mark Lord)
Newsgroups: comp.os.msdos.desqview
Subject: Re: Perstor ARLL controller and DESQview
Message-ID: <6999@bwdls58.bnr.ca>
Date: 3 Jun 91 19:21:05 GMT
References: <31MAY91094739@vms.huji.ac.il>
Sender: mlord@bwdls58.bnr.ca
Reply-To: mlord@bwdls58.bnr.ca (Mark Lord)
Organization: Bell-Northern Research, Ottawa, Canada
Lines: 44

In article <31MAY91094739@vms.huji.ac.il> gilf@vms.huji.ac.il writes:
<Hi All,
<
<I have been having problems working with a Perstor ARLL.
...
<However, since I installed this controller, DESQview hang, in almost
<every session, and communications are interupted. The dealer I baught
<the controller from refuses to acknowlage the problem, puting is down
<to the software (what else).
<I have heard elsewhere the Prestor and Zmodem conflict, and that Perstor 
<is sending a fix for it, but my mail to Perstor was returned stamped
<"Service Discontinued".
<Does anyone else have any information? I think the problem is that the 
<Perstor controller 1) uses memory locations that conflict with DESQview,
<and, 2) uses an interupt that conflicts with communication.
<Does anyone have any idea if those problems can be resolved using software

Bizarre.. I have a 16-bit Perstor ARLL in my system, with two floppy drives,
two different hard drives, and a tape drive hung off of it.  Desqview is my
primary operating environment.  Never a problem.  And ZMODEM (DSZ) is almost
always in use in a background window, at 9600bps.

There are a couple of possibilities here, the most likely of which is:

	- a disk caching program that buffers a whole track at a time.
	 Since the Perstor tracks are 31 sectors vs. the usual 17 (MFM),
	 this could result in a very long interrupt latency when the disk
	 cache program uses EXTended memory:  all EXTended memory transfers
	 are performed with interrupts disabled.  

	The solution to this is to a) specify a smaller limit on maximum
	number of sectors to "read-ahead" or a limit for number of sectors
	per XMS transfer (XMS = EXTended memory manager).  b) An even better
	solution is to install a 16550AFN serial chip in place of whatever
	you currently have for the serial port.. and use a comm program that
	knows how to take advantage of the FIFO on this chip.  This can improve
	tolerance of longer interrupt latencies.
-- 
MLORD@BNR.CA  Ottawa, Ontario *** Personal views only ***
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