Evergreen Rev-to-486 Processor
Daniel Beutel
"we don't support third party products" or something like that. What I
would like to know is this: Is there ANY way to disable/remove the
processor in the Tandy 2500 SX/33 to add an upgrade processor. The
upgrade is the Evergreen Rev-to-486. The current processor is NOT
socketet, but if there were a way do disable it and "piggyback" the new
one on top of it...Well, if anyone has any ideas, please let me know.
Daniel Beutel
dbe...@jasper.knox.net
John Girash
>would like to know is this: Is there ANY way to disable/remove the
>processor in the Tandy 2500 SX/33 to add an upgrade processor. The
>upgrade is the Evergreen Rev-to-486. The current processor is NOT
>socketet, but if there were a way do disable it and "piggyback" the new
>one on top of it...Well, if anyone has any ideas, please let me know.
The Revto486 does already disable the 386sx chip that you snap it onto.
I did fairly extensive research into these upgrades before trying the
Evergreen clock-doubling version on a 2500sx/25. To make the story short,
I'll tell it in point form:
-- both Evergreen and their competitor Improve Technologies (who make the
"Make-it-486") claim that their chips work in the 2500sx, but won't
clock-double (* see below) But most of the performance increase comes
from the 8k on-board cache anyway.
-- Improve admits that their product won't work with the Phoenix BIOS
v1.10.x or earlier (our 2500 has 1.10.00); Evergreen claims theirs does.
-- I spent 3 days trying to get the Rev-to-486 to work stably. It was fine
with the cache disabled, but no faster than the old 386sx. With the
cache enabled it would freeze or give GPFs in Windoze nomatter how much
I played with BIOS, config.sys or autoexec.bat settings. Evergreen
tech support claimed that I had faulty memory, but I don't buy it.
We have 6Megs on the machine, but even going down to just the 2Megs
soldered onto the mb didn't help. All is 70ns, and works rock-solid
without the Rev-to installed, or with it in but the cache off.
-- Cyrix claims that their upgrade chip works in a 2500sx, even when clock-
doubling. Oddly enough, Improve claimed that Cyrix was lying about this.
But the Cyrix costs more and only has 1k cache. Still, I've actually
heard from someone who got it to work in their 2500sx, after having the
same problems with the Evergreen that I did.
So in short, I'd stay away from the Evergreen & Improve, but if you want
to try the Cyrix I'd love to hear if it works.
(*) all this only applies to the version of the Rev-to-486 that's meant to
clock-double, which it's only designed to do for up to a 25MHz external
clock. But since it won't double on any 2500sx, the fact that yours is a
33MHz box won't matter. There's another version of the Rev-to that clock
triples for 25MHz or less, & clock doubles at 33. It's based on a totally
different chip than the doubling one, so maybe it'd work in a 2500sx.
Another point to consider is your 387sx brand: all 3 makers claim that
their chips will work with Intel (post-1986) or Cyrix coproc's, but only
about 10% of IIT's and 1% of ULSI's, 'cause those latter two don't conform
to IEEE floating-point standards. It was tough to get a straight answer
from Evergreen about this.
After all this, I've decided to look into upgrade motherboards: does anyone
out there know if there's a true 486 board that'll fit in a 2500sx case?
I realise that the daughtercard riser board for the expansion slots &
slimline case with built-in ports etc make this tough, but maybe Tandy
or IBM carried this design over to 486's?
hope this helps.
jg
--
"don't listen when you're told / about the best days in your life : Spirit of
a useless old expression, it means / passing time until you die." : the West
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-- John Girash --- gir...@cfa.harvard.edu --- http://skyron.harvard.edu/ --