#A2386 CPU Upgrade
21 messages in this thread
Dear All,
Is there anybody with CPU upgrade experience, e.g. Cyrix 486SLC2 25MHz,
which will double the A2386 BB?
What's about the Buffalo 486 Powerkit, advertised in Computer Shopper?
TIA
Bruno
Bruno,
I have the Cryrix upgrade in my A2000, it boosted my bridgeboard from
a Norton SI of 13.9 to 66.5! after a month of use I can find no problems
or incompatibilities of any kind – it is VERY much worth doing.
Gary
Gary,
thanks! I was wondering if it was worthwhile, or heck, even if it'd
work. Perhaps a review uploaded to lib 12 might be worthwhile?
Brian,
This is a great idea, maybe Gary will type in a short report in Marion's
CROSSINGS too! I think she will be delighted.
:-)' Bruno
Bruno,
Thanks! Actually, it's covered already. Several people have tried it–March
issue–and in April I have some caveats about space (it takes up an inch) and
the possibility of overheating, since there's no real room for a fan and that
chip runs hot.
Marion
CROSSINGS
Newsletter for Amiga/PC/Mac compatibility
Dear Marion,
I think my renewal fee came to late for the March issue.
Bruno
Gary,
Thank you very much for the fast reply. Please tell me a little more, e.g.
which Cyrix CPU, alone or mounted on a piggy-board, and what you was doing
exactly to make it work?
I think a lot of other users, like Brian, are also strongly interested to
hear the whole story.
TIA
Bruno
Bruno,
The entire process was quite easy, I ordered the Upgrade from ElekTek
in Chicago plus a Cyrix 387SX math coprocessor upgrade. The Cyrix upgrade
chip is their CX486SRX2, it is the only one that will work with the
Bridgeboard ( 20 or 25 megahertz no problem, if you have the original 16
megahertz bridgeboard then you need to run a software test supplied free
by Cyrix before you buy the upgrade – it may not work on these machines
).
The upgrade chip is mounted in a plastic carrier that clips firmly to
the surface mounted 386SX chip on the bridgeboard. Simply place the chip
over the Intel chip so the names are aligned and press down smoothly until
all four corners of the chip carrier "pop", this signals they have firm
contact with the original chip. Attach the included heat sink to the top
of the upgrade chip and the hardware assembly is finished. ( I added a 387
math coprocessor since the board was out of the computer anyway, line up
pin 1 of the coprocessor chip with the flattened corner of the socket on
the board and slowly apply pressure until the chip pops in ). Reassemble
the BridgeBoard into the computer and boot up, install the cache software
supplied by Cyrix to activate the chips on board cache and you are done.
The system performs far better than the original 386 based unit, Norton
SI was 13.9 on the unaccelerated system, it reports 66.5 on the Cyrix
based system. Windows 3.1 is actually quite usable now, MS Word and AmiPro
are fast and friendly and I can finally play DOOM!
Drawbacks are few, The chip carrier and heat sink are one inch tall so a
full size card in the next slot will likely be blocked ( I have a Supra
modem card in one end of the next slot and a Diamond Speedstar Video card
for DOS in the other end of that slot, they are both small enough that
there is no clearance problem ), the upgrade chip gets quite warm during
operation – use the heatsink!!! Cyrix gives a lifetime warranty on the
chip so that isn't much of a worry.
All things considered this is one of the biggest improvements for the
money I have ever made to my Amiga ( just did my brothers A3000, he is
very impressed! ). If you use DOS at all get this thing, it is worth it.
Gary
Gary,
thanks!
This upgrade sounds quite interesting. How much was the upgrade?
What about speed comparison with a 386DX? Is it faster or slower?
The upgrade is approximately $260 depending upon where you buy the chip,
Norton SI figures indicate it is about twice as fast as a 33 mhz 386DX. My
total cost was $318 including a math coprocessor and shipping charges.
Gary, do you have a 20MHz or 25MHz Bridgeboard? I've been thinking of
performing the Cyrix upgrade, but my board is 20MHz. I'd like to up it to 25
if possible. Any suggestions?
Tim Carter
Piedmont Publishing Co.
Tim,
You can do it easily by ordering the Cx486SRx2 20/40 upgrade kit, it
will clock double the chip internally to 40Mhz. The kit for the 25 Mhz
SX386 will not work with a 20Mhz BridgeBoard, make sure you order the
right kit. If you have specific questions just let me know.
Gary
Thanks Gary, but I guess what I'm asking is if it's possible to upgrade a 20MHz
Bridgeboard to 25MHz first, and then buy the Cyrix 25/50 Cx486SRx2 upgrade.
Any thoughts?
Tim Carter
Piedmont Publishing Co.
Tim,
this has to be general since I don't know the individual clock speed
ratings of the chips on the BB, and I just reassembled the beast, so I
don't want to take it apart to look. Usually, you can't upgrade from 20
to 25 MHz without a lot of work. At the very least, you need to replace
the CPU and to set at least one wait state in PCPrefs to allow for the
slower than normal RAM response, or replace the RAM. However, this
doesn't address whether the glue logic chips would work at the higher rate
of speed. Personally, I have no idea. The best thing you could do is to
buy a clock crystal, swap it for the existing one, and see how much
trouble the system encounters as a result. Generally, you can get away
with running the 20 MHz 386SX at 25 MHz, but it may not be reliable, nor
may it be safe. But, you should be able to test if it'll work at all.
If it does, then you may be able to get away with upgrading the clock
as well. I don't understand why you would be concerned with this since
there is a Cyrix 20/40 CX486SRX2 as well, but you asked, so here it is.
Brian,
One possibility, not guaranteed, is to simply replace the oscillator
with one for 25 Mhz. Depending upon the chips on the board, they may run
reliably (or not) at the higher speed. If the board runs flakey, it's simple
to re-install the old oscillator.
Steven,
yep. I thought I covered that option.
Can't see how you would do that – the 386 chip is surface mounted and I
sure would not want to risk cooking a board to dig one out. If you use the
correct Cyrix upgrade you will still be looking at a Norton SI of around
53 which is pretty decent MSDOS performance. I would definitely go with
that course if you feel the need for more power.
Gary,
Thank you again for your exact report. At last, please tell me the address
of ElekTek incl. Fax# and the name/price of the Upgrade kit.
Bruno
Bruno,
Please keep in mind that the 486 chip runs pretty hot and you need
plenty of air movement for proper cooling. Installing a small chip cooler fan
would be wise, but you will lose the adjacent slot because the upgrade plus fan
will take up more space than without the fan. However, the fan will provide
more reliable performance and may become necessary if the space around the 486
doesn't get much cooling air flow.
Steven,
Thanks, I have seen the CROSSINGS pic in the meantime.
Bruno