Abit BP6 dual PIII & PCI slots power & fans speed mods

Some time ago I got a BP6 mobo as alive and cheap example of hardware dual processor motherboard.

The mobo was equipped with dual 'mendocino' core celerons 333 SL36B. The celeron is reduced PII CPU in fact (MMX only) and with 100MHz bus overclocking, the dual SL36B 500 MHz CPUs are quite slow, there is no SSE and the total power consumption is quite high (especially for my 25A/5V power supply).

The 5V power problem is significant because of BP6 mobo design, the mobo uses 5V power channel to feed most parts of the mobo with 3.3V and less, but modern ATX V2 power supplies suggest 12V channel for the purposes. It is a problem to find 5V powered ATX power unit now. By the way, the additional power chips placed on the BP6 mobo dramatically reduce power noise for PCI and ISA buses, the working of mobo does not affect to all 'noisy' PCI/ISA adapters, that does not care about own power (so have no own power chips etc).

One rainy day i decided to upgrade the mobo. The reasons of the mods are:

Well, the mod step by step.

  1. I got the mobo with RU version of BIOS, that can detect and boot CPUs 'mendocino' only. To support 'coppermine' it is required to change CPU micro code table in BIOS.

    The abit bp6 BIOS is AWARD modual BIOS v. 4.5. There is AWARD tool to change BIOS modules (CBROM32_182.zip). 'Original' BIOS looks like this (original BIOS dump, original BIOS)

    I have added lastest HPT366 BIOS addon and all existing micro codes of the CPUs, that can fit into PGA370 socket, including 'coppermine' CPUs (mod BIOS dump, mod BIOS).

    To learn more about AWARD modual BIOS 4.5 look here (there is some text in russian)
    work with modules (dup link)

    To learn more about CPU microcode table look here (there is some text in russian) cpu-errata-new

  2. The second step is hardware compatibility of 'coppermine' CPU in FC-PGA socket and 'mendocino' CPU in PPGA socket. It is possible to easy make PPGA socket of the BP6 mobo compatible with FC-PGA also.

    Tere are lots of info about PPGA -> FC-PGA socket conversion in internet. By the way, the info shows, that it is not a good idea to make BP6 PPGA socket compatible with more powerful PIII 'tualatin' core CPUs in FC-PGA2 socket, the transformation requires special equipment and experience to work with smd chips and multy-level PCB; hardware requirements of FC-PGA2 socket (voltage levels, bus protocol) is more different from 'mendocino' one than 'coppermine'.

    Some notes about my PPGA -> FC-PGA socket conversion.

  3. Dual SMP work of different PIII CPUs.

    All existed info suggests, that in dual SMP mode both CPU must be the same: equal bus frequency, multiplier, cache size, stepping etc, in other words, they must be exactly the same CPUs and the only differences is serial number.

    But the mod shows, that two enough different PIII 'coppermine' CPUs with different: core voltage value, multipier and stepping can work together with BP6 in dual mode. They have equal bus frequency, opcode set and cache size only.

  4. Overclocking.

    The BX440 chipset is intended to work with 66/100 MHz FSB. It is known, there are lots of motherboards with BX440 that can operate up to 150 MHz. But the BP6 motherboard has bugs with tracing of signal and power wires, that do work with freq more than 100MHz FSB not reliable.

    The known way to win the bugs is change onboard power supply design, that lead to reliability with high frequences (for example).

    If you have chinese solderin iron for 1$ from neares shop only, then it will be not easy even solder out anything from the board, so, the only way to change bad by mobo design (if it is not changed yet) or damaged by time capacitors and stay with 100 MHz FSB.

    To remove damaged (blown up) capacitors you no need to solder out them from mobo. It is enough to break each of them by flat-nose pliers with intention to save pins of capacitors, the pins is already soldered to PCB. Clear the rest pins to dry state, use soldering flux for aluminium and solder new capacitors. And also, you can place new capacitors in horizontal plane above PCB.

    Overclocking with BX440 is depended from your AGP video card, that must support 89 MHz with 133 MHz FSB instead of 66 MHz for 100 MHz FSB.

    The low freq of FSB allow to set 2-2-2 SDRAM timing mode for SDRAM PC-133. The low memory latency is good thing and 110/2-2-2 often can be better than 124/3-3-3.

    Overclocking up to 110 MHz is quite reliable with my concrete hardware set. All case fans of CPUs and power unit working with 5V power silently and perfectly.

  5. Other problems.

    Some add-on PCI cards have own BIOS extention, the BIOS extention included into mobo BIOS or placed on PCI card is not working reliable (always). The work depends on PCI card order and in most times presence of AGP video card. This is BIOS bug, there are many BIOSes of other mobos, that can not boot or can not run BIOS extention from PCI add-on cards.

    Maximum multiplier is allowed by my BP6 BIOS is 8, so my 850 MHz celeron CPU looks like 800 MHz, but system can boot and is working perfectly.

  6. PCI addon card power 3.3V

    Most cheap modern PCI cards (USB 2.0,1G ethernet,SATA1) require 3.3V from motherboard, but BP6 has no the power voltage connected to PCI slots, the PCI pins are NC.

    It is interesting, that some of the cards can work even with 486 CPU mobo and oldest PCI versions only by 3.3V power connected.

    I was too lazy to sloder all power pins of all PCI slots, so for each used PCI addon card i select appropriate PCI slot, place mark to card with the slot number and for the cards, that require 3.3V, i check used by card 3.3V pins and connect power to PCI slot only to the pins, in fact in my case it was only one wire for each PCI slot, very easy. Of course, i am sure, that one PCI power line is enough for each conrecte card.

    To learn more about PCI 3.3V look here (there is some text in russian) tvtuner02

That's all.

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