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From: revatt@aluxp.UUCP (Robert S. Evatt)
Newsgroups: comp.sys.ibm.pc
Subject: Re: PCJR can it do cga (color graphics)
Message-ID: <876@aluxp.UUCP>
Date: Fri, 6-Mar-87 11:21:19 EST
Article-I.D.: aluxp.876
Posted: Fri Mar  6 11:21:19 1987
Date-Received: Sun, 8-Mar-87 10:44:08 EST
References: <1530@tekigm2.TEK.COM>
Reply-To: revatt@aluxp.UUCP (52153-EVATT, ROBERT S)
Organization: AT&T Bell Laboratories, Murray Hill, NJ
Lines: 33

In article <1530@tekigm2.TEK.COM> timothym@tekigm2.UUCP (Timothy D Margeson) writes:
>
>Both of these add ons seem to make the PCjr work almost as well as a PC. The
>big exception is the throughput, the PCjr is slower than the PC by about 30%.
>
>No add ons I know of help the speed issue, short of changing the clock freq.,
>and I have not tried that to see if it can be done (the clock in a jr seems
>to be used for many things besides running the CPU).
>

To the best of my knowledge, PROGRAMS RUNNING ENTIRELY IN EXPANSION
MEMORY (>128K) should execute as fast or faster on the jr than on the
4.77MHz PC.

There are two major impacts on speed with the jr:

     Throughput WILL be about 30% below the PC for execution in the
     bottom 128K because of contention between the display and the CPU
     for memory accesses.  Filling the 128k with a ramdisk or memory
     resident programs or using the PCJRMEM.COM driver (supplied with
     IBM's memory expansion sidecars) with the /C switch will eliminate
     the competition for memory accesses.

     The other main hit is the lack of DMA.  The only way around this
     are the RACORE units with DMA.

********************************************************************************
*       Robert Evatt                 [ihnp4...]!aluxp!revatt                   *
*       AT&T Bell Labs               (215)770-3570                             *
*       Allentown, PA 18103                                                    *
********************************************************************************
*                        usual disclaimers apply                               *
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