Path: utzoo!attcan!utgpu!jarvis.csri.toronto.edu!mailrus!sharkey!itivax!umich!dip.eecs.umich.edu!chuck
From: chuck@dip.eecs.umich.edu (Chuck A. Nicholas)
Newsgroups: comp.sys.ti
Subject: Re: Myarc Geneve
Keywords: Graphics capabilities
Message-ID: <181@zip.eecs.umich.edu>
Date: 14 Jul 89 17:24:41 GMT
References: <4752@psuvax1.cs.psu.edu> <1643@csm9a.UUCP> <176@zip.eecs.umich.edu> <5507@pt.cs.cmu.edu> <1657@csm9a.UUCP>
Sender: news@zippy.eecs.umich.edu
Reply-To: chuck@dip.eecs.umich.edu.UUCP (Chuck A. Nicholas)
Organization: University of Michigan EECS Dept., Ann Arbor, MI
Lines: 44

In article <1657@csm9a.UUCP> kamann@csm9a.UUCP (kamann) writes:
>In article <5507@pt.cs.cmu.edu>, bjm@RIO.MT.CS.CMU.EDU (Bret Musser) writes:
>>
>> Also, when you buy a machine like the Atari or Amiga with
>> their 68000's, you get much more memory addressable.
>> The 9995 is 16 bit.  It can address 64K.  As I recall,
>> the 68000 has a 20 or 24 bit bus so can access X megabytes
>> (sorry, I don't have a calculator here).  
>> 
>Is the Atari REALLY accessing X megabytes?  As I recall most architectures
>nowadays are built around a page-swapping facility, even IBM.  Let's take a
>good look at what has been said.  As most know the TI came standard with 16k
>on board.  You could then buy an additional 32k card for it.  But because of
>memory for the VDP, etc. the TI actually had around 64k.  Nowadays you can
>get gram/ram devices that give you a virtual memory that is somewhat 
>limitless (at least from my understanding of it).  Now, I know that IBM is
>designed around the concept of a 64k paging area (or the XTs were anyway).
>So I think it would be safe to say that an IBM only has 64k addressable also,
>or is it?!?  Now, is the Amiga/Atari designed around the same concept?
>I wasn't aware that they had 20 bit buses, but there is still a limitation
>to the amount of memory you can actually address, even BIG machines use
>page swapping mechanisms and virtual memory.
>

The 68000 family has a large direct addressable memory range, (16 meg I believe)
whereas the original PC's 8088 used 64 K pages to access the 2 meg of "real"
address space that it could potentially access.  The 80286 and 80386 expanded the
real memory, but not when running in 8088 emulation.  

Re clock speed versus processor performance, the 9900 family does not use the same
style of architecture as either the 68000 0r 80x86.  These chips have dedicated
registers wheresas the 9900 uses general memeory for most register operations.
I beleive it was Bill Gronos that wrote some benchmark software to run in the 4/a
scratchpad memory that ran rings around the similarly clocked 8088 and 6500 cpu's
of that time.  It is very misleading of Myarc to advertise the Geneve intimating
that the clock crystal speed is the rated speed of the processor.  They also do a
little number regarding memory by lumping in the 128 vdp ram with the 512K cpu

BTW, the TI emulation mode on the 9640 is a real pig of a program.  Doing a
chkdsk after loading GPL (graphics programing language) emulator and quiting
back to mdos shows over half of the 512K is gone.  MDOS only occupies about
80K so the gpl mode takes up almost 200K. 

chuck nicholas