[KLUG Members] Difference Between Athlon and Athlon Thunderbird

[Bryan J. Smith]

Sanjay Chigurupati wrote:
> Hi,
> I was just wondering what the difference between
> Athlon and Athlon thunderbird is.

                       Interface     L1      L2       FSB
Athlon                 Slot-A        128    512@1/2   200
Athlon Duron           Socket-462    128     64@1     200
Athlon Thunderbird     Socket-462    128    256@1     200
Athlon 4               Socket-462    128    256@1     200-266
Athlon MP              Socket-462    128    256@1     266

All Socket-462 Athlons _are_ dual-processor capable, the MP just
seems to accel at such configurations (by upto 15%).  The new Athlon
4 is lower power (upto 25%), improved branch prediction unit **, and
a few other details.  The "Duron" is usually a "rejected"
Thunderbird that has some damaged L2 during fabrication (very
common) where the L2 is split up into 4 "regions" and 3 are "cut
away" before packaging.

-- TheBS

** Note:  The branch prediction units of any AMD processor, K6 and
above, are superior to any Intel processor ever produced.  The best
branch prediction unit was on the K6 series (which was designed by
NexGen for their Nx686 which AMD bought), which was close to 98%
accurate, and totally overkill for the number of transitors used
(almost 3M transistors = ~25% of the CPU!!!).  When the K7/Athlon
was designed, the design was scaled back to only about 94% accurate
(at a transitor cost <<1M).  The new Athlon 4/MP has one that is
about 97% accurate that costs about 1M transitors.  When the Athlon
"stalls" on a branch mispredict, only about half the pipes are lost
(~19 stages/pipe, 9 pipes).  The best branch prediction unit of any
Intel processor is the P3, which was about 92% accurate and had half
the number of stages in its pipeline so its full stall is not as bad
(9 stages/pipe, 5-6 pipes).  The P4 is less than 90% accurate and
has a huge stall on a mispredict where everything is lost (~20
stages/pipe, 7 pipes).  The IA-64/Itanium doesn't use branch
prediction but branch predication.

-- 
Bryan "TheBS" Smith  mailto:b.j.smith@ieee.org  chat:thebs413
Absolute Value Systems, Inc.        http://www.linux-wlan.org
SmithConcepts, Inc.              http://www.SmithConcepts.com