Re: If you could design a $300 homecomputer today, what would you choose?

[Roy Miller <millers@inebraska.com>]

william strutts wrote:

> "Timothy A. Seufert" <tas@mindspring.com> wrote in message
> news:tas-16D91B.21514716072001@news...
> <snip>
> > I believe you are 100% wrong in stating that Apple II programs never
> > exceeded the "size of memory space" (I assume you mean 64K).  Unless I'm
> > grossly mistaken, AppleWorks did just that.  It was and is quite
> > possible to design programs which bank switch code and/or data in and
> > out of the CPU's address space.  With care, it need not even be a pain
> > in the butt.
>
> I did say that they would have to be bank switched.  It would still
> need an address range to move the data to like that extra 64K on
> the 80 column IIe card does.  It is bank switched. What I meant
> in saying they didn't exceed the size of memory was that only
> 64K could be accessed at one time.

Sometimes one's thoughts and what one types aren't always the same. Perhaps
that is why your last sentence is nonsense. Many programs for 64K 8 bit
computers were larger than 64K. Some 8 bit machines used bank switching, some
used overlays, and some used both (WordPerfect for the 128K ProDOS Apple //e
or //c would run MUCH faster if one added extra memory and formatted it as a
disk drive, copied the files to the RAM disk and launched the program from
the RAM disk. Neither ProDOS nor WordPerfect did any "bankswitching", only
the loading of overlays from a disk.

> To get more memory requires
> the programmer to bank switch the program or to swap code
> out and pull it from the Floppy/HD in his code.  No hardware
> or OS automatically handled that on the Apple II.

But then, the machine that you protest would cost too much would easily do
that. As I recall the 128K Mac used "virtual memory". Was that the ability of
the 68000, or the OS, or both? And why couldn't it be done on this machine
inexpensively?

> The early
> PC's like the 286

The early PCs, of course, used 8088 and 8086 chips.
The second generation, "Advanced Technology" machines used their 286 and
later 386 CPUs as fast 8088/86s.

> had all kinds of odd ball memory due to the
> 8-bit legacy of the 286 processor.  They still had 64K code
> segments and any one chunk of code had to reside on a 64K
> bank.  You don't want to place a loop on two banks of memory
> because that would require you to bank switch constantly.

Of course, you have the same situation with the IIgs, because the 65816 has
segmented memory.

>
>
> > For software like a RAMdisk, it's not a pain in the butt at all to use
> > bank selection.  No different from selecting what sector of a disk drive
> > to read in a driver for an ordinary electromechanical disk.
>
> While that is true, it requires special coding on the part of the
> program.

No, it doesn't. It only requires RAM disk software. *IF* by special, you mean
the ability to use a RAM disk as opposed to a floppy disk or hard disk.
Again, overlays were VERY common in the late 70's and early 80's. Memory cost
too much, so programers had to use disk space. Besides, you have shifted the
point. You said the problem with his machine was very expensive additional
hardware. Nothing about additional code.

> Not all Apple IIe programs supported the extra RAM
> and it was the minority that did.  The program had to be aware
> of the memory.  Some smarter 8-bits using the 6809, had a
> MTU unit which would take care of the bank switching.  They
> had a smart operating system called OS-9 that knew how to
> handle the memory plus it had a hardware chip which handled
> a lot of the memory management.
>
> The other way was using the Chain command in the older
> basics which would remove the app in memory and load
> the referenced code.  Not all Basics had that command. That
> made it a bit easier but on the Coco, it required the programmer
> to write routines to access the memory.  It was not handled
> automatically by the OS.

None of the above however deals with the erroneous conclusion that 64-256meg
of RAM disk would require expensive additional hardware to use with a 68000
CPU.

Roy

>
> --
> --
> William R. Strutts - wrstrutts1@nospam.home.com - Whatever!
>
> C'est moi!  http://www.facelink.com/wrstrutts
>
> Just hacking away...
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