It seems that there are a lot of questions regarding the Cyrix 386 compatible
486DLC and 486DRU2.  My info comes directly from Cyrix's Fast Fax service:
And also from installing one of these chips in an IBM Model 80.

The 486DLC is a 486 instruction set compatible CPU which fits into a 386DX
socket (Pin Grid Array, or PGA).  The DLC currently is available in 3 speeds.
the 25, the 33, and the 40.  They do not have a coprocessor on board, but any
software query will return coproc as present.  I guess they emulate the
coproc instructions.  Math functions are on the 386DX level without the
actual coprocessor.

The internal cache on the 486DLC is 1K.  Cyrix literature claims a 85% hit
rate.  My informal tests show that the cache accounts for a 10% performance
boost when it is enabled by software.  Overall performance boost from a
386DX-25 to a 486DLC-25 is about 60%.  The benchmarks I used were NU SI and
QAPlus Dhrystones and Whetstones.  The performance, with the cache enabled,
is about on a par with my 386DX-40 with 256K external CPU cache, which is
around the performance for a 486SX-25.  The computer runs noticebly faster,
and DOS 6 with Dblspace is not complaining.  The company claims OS/2
compatibility, but I didn't test it.

The 486DRU2 is not a chip, as commonly thought.  The 486DRU2 is actually
a small daughterboard slightly larger than the 386DX, which contains
the logic to manage the clock doubler.  This board plugs into the 386DX
PGA, and the 486DLC-33 or 40 plugs into this board.  I guess the board
doubles the frequency apparent to the CPU, and insert wait states when 
access to the rest of the system is required.  There are no info available
from Cyrix there.  Anyway, the DRU2 is available for 386DX-16, and 386DX-20
only.  Double these clock rates, and you get the 32MHZ and the 40MHZ DLCs.
If Cyrix is planning to do the same thing for the DRU2-50, then they need
to put out the 50MHz DLC2 first...

I also tested a DLC33 motherboard, along with a Cyrix Coprocessor.  With 64K
external cache, performance were about 30% faster than the 25, but still
significantly (25%?) slower than an actual Intel 486DX.

IMHO, the DLC is a great, low price upgrade for people who can't afford, or
can't install, a new motherboard.  It is definitely worth what I paid for it,
but if you need 486DX-33 performance, the DLC33 won't cut it.  I'm not sure
about the DLC-40, but I think even if it matches the performance, it won't
beat it in any significant way.

The last time I posted info about the DLC, people sent quite a bit of mail,
asking where I got it.  So here is where I got mine:

Treasure Chest peripherals, they advertise in the Computer Shopper.
1-800-677-9781
The 486DLC-25 kit was $179.00

But....

I liked the chip so much that I found the supplier, and became a dealer.
If you are interested in the chip, e-mail me, and I can fax or mail you
more info.   I'm well aware of the net's policy against commercial use,
So I can;t post anymore info here.  However, if there are more questions
regarding the 486DLC itself, I'll post what I can.

jamesc
909-396-0408

