Chris Tribo wrote:

> On Tue, 20 Mar 2001, John Maier wrote:
> 
> > My Goal?  To either make a replacement board or devise a method to upgrade
> > an existing /2x0 to a bit more speedy technology.
> > So far the IDT9R3081 (http://128.11.21.63/docs/79R3081_DS_3483.pdf) looks as
> > if it may be a good CPU replacement with the help of a MQUAD/PLCC(84) to
> > PGA(144) adaptor (most likely a custom job) This would allow the board to be
> > ramped up to 50Mhz and get a bigger I/D cache.  However, the 50Mhz version
> > is a 5.0V chip, so I don't know if this available to the board without a
> > little wire hack :-)
> > 
> > As for the R4400 based /260, all I know is the R4600(133Mhz)chip is pin
> > compatible with the R4400 but has some issue that can be address with some
> > pin modifications per MIPS webpage
> 
> 	There would also be some software issues in dealing with three (or
> four?) different processor designs, but certainly not insurmountable (with
> the proper know how)

At this stage, I'd suggest the software CPU support is your smallest
problem.  There might be a small amount of pmax-specific rework, but
in general I don't think this bit will be too much at all.  Put it
this way - if you get a working design, we'll make the software work.

> > http://www.mips.com/Documentation/R4x00_common_design.pdf IDT make a R4400
> > based chip that may be a candidate for a retrofit
> > http://128.11.21.63/docs/79RC64474_DS_53993.pdf
> 
> 	133MHz would certainly be a _little_ bit of a speed boost.

Emphasis on _little_ here.  DEC and everyone else seem to have different
ideas about CPU speeds for the R4x00.  These CPUs are internally
clock-doubled - what DEC calls a 60MHz part everyone else would seem
to call a 120MHz part.  So a 133MHz CPU would be a 5000/266 (or
something!).

> > I know this isn't really the forum for such a discussion, so if someone
> > insists that I take this offline, no problem.
> 
> 	Nonsense, this is probably the only forum, next to 
> comp.unix.ultrix and the OpenBSD pmax mailing list.

Agreed :)  There's probably more than a handfull of /240 owners on this
list who'd like to see something a little faster.

Best of luck with your project!

Simon.
--
Simon Burge                            <simonb@wasabisystems.com>
NetBSD CDs, Support and Service:    http://www.wasabisystems.com/