Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!csd4.milw.wisc.edu!lll-winken!uunet!portal!cup.portal.com!A-N-Onymouse
From: A-N-Onymouse@cup.portal.com (John - DeBert)
Newsgroups: comp.sys.cbm
Subject: Re: what is this chip(65C802)
Message-ID: <16510@cup.portal.com>
Date: 31 Mar 89 20:52:36 GMT
References: <41063@tut.cis.ohio-state.edu> <6460@cbmvax.UUCP>
Organization: The Portal System (TM)
Lines: 91

In article <6460@cbmvax.UUCP> daveh@cbmvax.UUCP writes:

>in article <41063@tut.cis.ohio-state.edu>, calhoun@cis.ohio-state.edu (robert r calhoun) says:
>
>> 	While I was researching the 6502, I came across	a 65C02 which is a 
>>	CMOS 4MHZ version of the 6502.  I noticed also that there is a 65C802.
>>	From what I know, this appears to be an	Advanced CMOS 8MHZ processor.  
 
There are some books out about programming the 65C802/65C816.

>
>Sounds like you've been reading GTE databooks.  One caution -- don't believe
>everything you read.  While these databooks often show the timing for parts
>in a wide variety of speeds, that doesn't necessarily mean that such parts
>are actually available.  Last time I looked, GTE listed 65C02s up to 4MHz and
>65C802s and 65C816s up to 8MHz, though they only had 4MHz versions of the
>latter, and no real yield on the former at 4MHz (they probably have the
>4MHz 65C02s by now...).

Hmm. I have before me a copy of a data sheet for the WD65C816/65C802 that
specifies a version of the device with an 8MHz clock. It's >NOT< a preliminary
data sheet.

>
>>	He now wants me to rearrange his C64 to use the fastest 65??02 I can 
>>	find.  If the 65C802 is truly an 8MHZ processor I calculate that he 
>>	will need 100ns memory chips.  I don't recall seeing 64k 100ns chips 
>>	so I guess I'll have to make it accept 256's.  
>
>Someone currently sells a little accelerator for the C64 that plugs into
>the cartridge port and runs up to 4MHz (check the C64 magazines).  You can't
>run at 8MHz using dynamic RAM; 100ns is just the RAS access time.  A minimum
>cycle time for such a part is 180ns.  Also consider that, even though the
>cycle time of an 8MHz part (which you probably can't get anyway) is 125ns,
>you can only use a fraction of that time for your memory access.  There's
>a wait for addresses to be valid (probably around 1/4 or so of the cycle),
>and a setup time for data to be valid before the processor clocks it in.  Not
>to mention any external logic needed to multiplex the address lines from the
>CPU to the DRAM and for decoding.  The 4MHz C64 add-ons use static RAM,
>probably 100ns parts.  Note also that since the C64 uses a 6510, which has
>an on-chip I/O port, you'll have to come up with some way of emulating that
>port.

8MHz is too fast for DRAM? Shhh! Don't tell my HP! It has DRAM and an 8MHz
clock. Plus a faster one for the alphagraphics display. :)
 Seriously, one wonders how one may get DRAM to work with those so-called
turbo clones with clocks of at least 8MHz.
 Also, I have seen 70ns DRAMS advertised from time to time. 

>
>> 	With this idea, I would like to know if there is
>> 	a faster C64 video chip so that I won't have to continuously write
>> 	a copy of video ram to the old 150ns RAM.  The wait states would be
>> 	too harsh to consider.  Anyone who has tried any of these, I would
>> 	greatly appreciate learning from your experiences and mistakes.
>
>There are no faster VIC chips.  You'll have to come up with some clever
>scheme to make this work correctly.  I'm not exactly sure what the folks
>who make these accelerators do, but there are options.  One option would
>be to make like an Apple II GS.  Whenever your fast CPU writes to memory,
>you slow down to 1.02MHz and write to both normal C64 memory and your fast
>static RAM.  Same thing happens for read or write of I/O devices.  For
>straight memory reads, you can read full speed from your static RAM.
>
>Needless to say, this isn't a one-afternoon project.  Such an accelerator
>is going to require some clever hardware design.  Once it's done, you'll
>no doubt learn about "software timing loops" when a good portion of the
>C64 programs you have don't run properly.  Folks are selling these accelerators
>for more that the cost of a C64; much of that selling price is the cleverness
>you're buying.

 I doubt that it would be worth the trouble and expense to modify the C64
for "turbo speed" using the 65C802. There would need to be drastic changes
in bus timing and how interrupts were handled. After you're done with the mods,
you'll probably never be able to put the thing back in a C64 case. Even if
you just wanted to do a straight replacement of the 6510, there's still the
problem of how to implement the i/o port but that's not really too hard. 
  
Ah, well. Now that we've knocked your idea and all, perhaps you'll prove us
all wrong? :)

>-- 
>Dave Haynie  "The 32 Bit Guy"     Commodore-Amiga  "The Crew That Never Rests"
>   {uunet|pyramid|rutgers}!cbmvax!daveh      PLINK: D-DAVE H     BIX: hazy
>              Amiga -- It's not just a job, it's an obsession

J. DeBert
A-N-Onymouse@cup.portal.com
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