Eventually, we may be seeing locked Tbred B 1700+/1800+ DLT3C. Since the 1700+ has the same 11x multipler as the Barton 2500+, here is what I think the impact would be - not much, ...
This is a modified version for the analysis for the locked Barton 2500+, applied to locked 1700+/1800+.
Locked Barton 2500+ or locked 1700+ DLT3C are still the best choice in terms of CPU overclocking, FSB overclocking and price (on air)
This was written for Barton 2500+ w/ 11x multiplier, same argument would hold true for a locked Tbred B 1700+ DLT3C.
For a locked 1800+ whose multiplier is 11.5, it becomes borderly good as the locked multiplier limits the FSB overclocking by about 4% (or about 8 MHz).
As long as you have a nforce2 rev 2.0 motherboard (running at FSB 220 MHz +- 10 MHz), keep the locked Barton, its x11 multiplier works nicely with good HSF on air, from 2.31 - 2.53 GHz depending on how high the FSB and memory can be pushed.
Don't get the higher PR rating CPU, it costs more and it may make things worse, if you have a 210 or higher FSB motherboard. Same argument, don't get locked CPU with multiplier higher than 11x or 11.5x
E.g. assuming the Barton series can be overclocked to around 2.5 GHz,
if you get 2800+, if it is locked at x12.5, and your FSB would be limited to 200 MHz. Memory intensive applications and benchmarks may not perform as well as a Barton running at 2.475 GHz using 225 FSB x 11. The lower 25 MHz in FSB in the case of 2800+, is about 25 (8) (0.95) = 190 MB/s lower in effective memory bandwidth.
1700+/2500+ default multiplier 11
1800+/2600+ default multiplier 11.5
2800+ default multiplier 12.5
3000+ default multiplier 13
3200+ default multiplier 11
To summarize,
Assuming the Barton series can be overclocked to around 2.5 GHz using a high end copper HSF such as SLK-800/900/947U,
A 1700+/2500+, locked at 11, FSB would be limited to 227 MHz
A 1800+/2600+, locked at 11.5, FSB would be limited to 217 MHz
A 2800+, locked at 12.5, FSB would be limited to 200 MHz.
A 3200+, locked at 11, same as 2500+, FSB would be limited to 227 MHz.
There is a good chance to achieve 220+ FSB w/ a NF7-S rev 2.0, with winbond memory BH5/CH5, enough Vdimm and chipset Vdd.
So Tbred B 1700+/1800+ DLT3C or Barton 2500+ is still the best choice for locked CPU in terms of CPU overclocking, FSB overclocking and price.
Goal for 24/7 system:
- 2.5 GHz 512 L2 cache Barton 2500+ (SLK- HSF) OR
- 2.5+ GHz 256 L2 cache 1700+/1800+ DLT3C (SLK- HSF)
- 227 FSB x 11 (NF7-S rev 2.0) (for 1800+ FSB would be limited to 217 MHz)
- memory w/ winbond CH5/BH5 chips
- $90 CPU for Barton OR
- $50-60 for 1700+/1800+
That is, the FSB and the CPU would have a good change to be maximized out at the same time, without using the more expensive 3200+ (which also has x11 multiplier).
Impact of Tbred B 1700+/1800+ DLT3C or Barton 2500+ w/ locked multiplier on overclocking
Putting things into perspective, currently for system with NF7-S rev 2.0 with CPU on air cooling, the impact of locked 2500+ is minimal, at most 3% from best overclocking (2.5 GHz), if the motherboard and memory can do 220 MHz.
If aiming for super FSB to 240-250 MHz for 3Dmark benchmark, then the CPU is limiting the FSB due to the fixed 11x multiplier.
If motherboard or memory is limiting at the low 200-210 MHz, then the FSB is limiting the CPU to 2200-2310 MHz.
If there is no workaround for the locked Barton, these would be the scenarios:
1. It would mostly affect users with KT266A, KT333A motherboads, since those boards can achive max FSB around 150 MHz and 190 MHz respectively, due to 4:1 and 5:1 PCI lock, .... As a result, a Barton 2500+ with 11x multiplier, the max CPU overclocking frequency would be 1650 MHz and 2090 MHz respective. These number are way below the norm of 2.2 - 2.4 GHz for Barton 2500+.
2. It would also affect users using extreme coolings. Assuming they are using nforce2 which can do 220 MHz FSB on the average, and as high as 240+ if using enough Vdd, Vimm and chipset cooling, and "good" RAM, ... So the Barton 2500+ in these systems with 11x multipliers would be limited to overclocked frequency of 2420 MHz (220 FSB) to 2640 MHz (240 FSB). Not 2.7 - 2.9 GHz as hoped for. One would need a Barton with 13x multiplier to achieve 2860 MHz running 220 FSB.
3. For air cooling using a good nforce2 motherboard such as NF7-S rev 2.0, whose FSB averages around 220 MHz +- 10 MHz. The Barton 2500+ should still be able to run at 220 x 11 = 2420 MHz, which is above the norm 2.3 GHz for Barton 2500+. At FSB 230 MHz, which is doable, the Barton would then run at 2530 MHz.
Now the burden becomes putting more demand on the FSB, memory, and how to tune/optimize the FSB reaching 220 - 230 MHz, so that the motherboard, good memory (modules with WinBond CH5/BH5 chips) and FSB are not holding back the Barton 2500+ due to the fixed multiplier 11. If one can only achieve FSB 210 MHz, the Barton would be running at 2320 MHz, which is still above the PR rating of a 3200+ AMD processor.
To achieve 2.3 - 2.5 GHz speed for a 2500+ on air, a copper HSF such as SLK-800/900/947U and a high CFM adjustable fan such as TT SFII would be the choice. It is doable with a TT SFII fan running 3000-3200 rpm at which the noise should be acceptable for 24/7 run. Barton 2500+ at 2.3 - 2.5 GHz can run few degree C cooler and less power than a Tbred B 1700+/1800+ DLT3C delivering the same overall performance.
So I would say at multiplier 11x, currently with high end air cooling, for system w/ nforce2 rev 2.0 board, there is not much an impact for 24/7 usage:
- The impact is at most 12% (2200 MHz at stock FSB 200 MHz) on CPU frequency from the best Barton 2500+ overclocking on air (assuming 2500 MHz). Even in this worst case situation, it is already running as a 3200+ CPU.
- An average system at FSB 220 MHz can run Barton at 2420 MHz (about 3% off the best Barton at 2500 MHz on air).