ta0e#@andrew.cmu.edu.UUCP (03/03/87)
In response to a query by Ted Medin dated 3 Mar 87,
>Will the jr handle cga and if not what do i need to look like cga?
My experience with the PCjr has been that most packages which require
a CGA (color graphics adapter) will work on the PCjr with no problems. I say
most because there are some packages which write directly to screen memory
and bypass DOS's handling of screen I/O. Since the PCjr's memory is arranged
differently than the rest of the PC family, this does present a problem. I
know that screen drivers exist for some packages (eg. Lotus Ver. 2) and can
only suggest you check with the manufacturer if one of your packages does not
work.
Sharif Abdallah
(Student : Carnegie Mellon , Mail to TA0E@Andrew)timothym@tekigm2.UUCP (03/04/87)
>In response to a query by Ted Medin dated 3 Mar 87, >>Will the jr handle cga and if not what do i need to look like cga? Hi, The PCjr WILL also emulate the CGA sufficient to run programs such as these: Framework II, dBase III, Lotus, Symphony, among others... all of which will write directly to video memory. The trick is they all look for where video starts by reading vectors in the DOS area, so as long as this area is set up appropriately, all works well (I think). The trick is to use a program (actually a driver) such as CONPCJR supplied with the Techmar side car, or the configuration program supplied with the Racore 2nd disk expansion (which is now more reasonably priced, #2 floppy for about $300.00, a 20meg HD for about $600.00). 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). -- Tim Margeson (206)253-5240 PO Box 3500 d/s C1-937 @@ 'Who said that?' Vancouver, WA. 98668 {amd..hplabs}cae780!tektronix!tekigm2!timothym (this changes daily)
revatt@aluxp.UUCP (Robert S. Evatt) (03/06/87)
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 * ********************************************************************************
smvorkoetter@watmum.UUCP (03/06/87)
The PCjr has hardware that allows you to write to the screen where it is found in the PC, at B8000. This is automatically and transparently redirected to wherever the video buffer might be (as moved by CONPCJR). As far as speed is concerned, if you have the Racore expansion, with 384K of 0-wait-state memory, and you fill up your 128K jr base memory with a RAM disk, a PCjr is actually about 30% FASTER than a PC. Also, depsite the lack of DMA, PCjr disk I/O is faster than that of a PC, but I am puzzled as to why this is so. Maybe it reads into bigger buffers to compensate for lack of DMA, and outperforms its cousins doing so.