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  1. #1
    ROG Enthusiast Array AllGamer's Avatar
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    ASUS P55T2P4D cmos battery

    Does anyone have a clue what powers the ASUS P55T2P4D cmos?

    I have this classic motherboard stored away in a closet for more than 10+ years, and to my surprise when I powered it ON, the time date and BIOS settings are still intact!
    It showed the correct time and date!

    Most other motherboards from that era, including ASUS P2B, ran out of CR2032 battery long long time ago.

    This P55T2P4D doesn't have a CR2032, not sure what it uses to keep power.



    I got it running with Dual 233mmx + 512 RAM with a few Dual port PCI intel MX Gigabit cards to run pFsense Firewall

    It was too slow for NAS server, but fast enough for a Router / Firewall.

    This is one of those unique motherboards that you want to keep forever for its rarity, back then, and even now.
    i7-3970X, Corsair H80, 32GB G.SKILL, ASUS RAMPAGE4 Formula, ASUS VG278H(3x27") & 3D Vision2, EVGA GTX 690(2x) 5760×1080*3D, OCZ ZX 1250W, OCZ 256GB Vertex4(2x), Seagate 3TB(6x), Antec LanBoyAir, Logitech G510, G600 & Z560 THX, Sennheiser PC163D, TrackIR5, Thrustmaster T.Flight Hotas, Saitek PZ35

  2. #2
    ROG Guru: Orange Belt Array Ntwlf PC Specs
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    Ntwlf's Avatar
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    Hi AllGamer,

    That is a classic board. I hadn't known anything of it, until searching for info to answer your question.

    So here is what I have found...

    This board is in the same model range as yours so may not be identical, but I think you will find the component (chip) I'll be referring to. At top of pic (click to zoom), near the upper left corner you'll see a black box on the board that has stamped on it "DALLAS, DS12B887, REALTIME, 9702A2, 088165, & pic of Alarm Clock". This is the CMOS Clock and the battery is integrated within. The entire chip must be replaced should the battery fail. Research has indicated some manufacturers has these removable/plugged into a socket. You'll have to look at your own board to verify.
    http://computer-retro.de/Bilder/Main...-Bios-1996.jpg

    This link is a manual for the "P/E-P55T2P4D" motherboard. There is a pic on page 9 with text identifying some components. The "Self-Powered RealTime Clock" is identified, although the picture is blurry.
    http://www.motherboards.org/files/ma...5t2p4d-200.pdf

    Please read on this page, at title "BIOS and CMOS Ram"...
    https://books.google.com/books?id=E1...0Clock&f=false
    Here's more info, at title "Obsolete and Unique CMOS Batteries"...
    http://www.tomshardware.com/reviews/...n,3066-10.html

    Should you need to replace it, if it's socketed. Here's the "DALLAS DS12B887" from a seller on ebay...
    http://www.ebay.com/itm/DS12B887-DIL...AAAOxyLN9Smgm6
    You only need to match the "DALLAS DS#" (example 12B887) on the chip. The 2 strings of numbers below "REAL TIME" refer to batch numbers, build date, factory code or something along those lines.

    Interesting reads...
    http://www.geekzone.co.nz/forums.asp?topicid=102640

    http://www.mcamafia.de/mcapage0/dsrework.htm

    http://images.ihscontent.net/vipimag...DALLS123-1.pdf

    http://50.112.106.113/DS12B887%20Rea...datasheet.html

    Be sure and read "Will replacing the clock module fix my PC?" on page 2.
    http://www.datasheetarchive.com/dl/D...DSA0029613.pdf
    Last edited by Ntwlf; 05-17-2016 at 07:28 AM.

  3. #3
    ROG Enthusiast Array AllGamer's Avatar
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    Thank you, thank you, thank you Nite Wolf, those are some good reads, specially the dallas PDF and toms hardware topic about CMOS.

    I'm really grateful mine is working great, but is good to know, which part to replace if it ever breaks down
    which is actually what this topic was all about, just trying to figure out how to recharge / replace the battery which I couldn't find, if it ever runs out.

    I was just amazed that this little CMOS can run for so long (18 years) since the last charge before I put it away for storage so many years ago.
    Last edited by AllGamer; 05-17-2016 at 08:26 PM.
    i7-3970X, Corsair H80, 32GB G.SKILL, ASUS RAMPAGE4 Formula, ASUS VG278H(3x27") & 3D Vision2, EVGA GTX 690(2x) 5760×1080*3D, OCZ ZX 1250W, OCZ 256GB Vertex4(2x), Seagate 3TB(6x), Antec LanBoyAir, Logitech G510, G600 & Z560 THX, Sennheiser PC163D, TrackIR5, Thrustmaster T.Flight Hotas, Saitek PZ35

  4. #4
    ROG Guru: Orange Belt Array Ntwlf PC Specs
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    Ntwlf's Avatar
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    Your "Very Welcome" AllGamer.

    It's quite impressive of the battery life on the DALLAS chips, but the replaceable coin battery on equipped motherboards is most preferred even with it's shorter life span.

    Since I don't know your skills at modding the chip, I did my best at providing the most pertinent information should it fail (dead battery), but you may know someone who could help you should you need/chose to do this. I prefer the mod method (adding a coin battery) to replacing the chip as it's the simplest with my skills, but your situation may be different.

    I appreciate your "Thank You's".

  5. #5
    ROG Enthusiast Array AllGamer's Avatar
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    Last edited by AllGamer; 05-20-2016 at 02:29 AM.
    i7-3970X, Corsair H80, 32GB G.SKILL, ASUS RAMPAGE4 Formula, ASUS VG278H(3x27") & 3D Vision2, EVGA GTX 690(2x) 5760×1080*3D, OCZ ZX 1250W, OCZ 256GB Vertex4(2x), Seagate 3TB(6x), Antec LanBoyAir, Logitech G510, G600 & Z560 THX, Sennheiser PC163D, TrackIR5, Thrustmaster T.Flight Hotas, Saitek PZ35

  6. #6
    ROG Guru: Orange Belt Array Ntwlf PC Specs
    Ntwlf PC Specs
    Laptop (Model)Build Below In Progress
    MotherboardASUS Maximus VII Formula
    ProcessorIntel i7 4790K @4.8GHz (siliconlottery.com)
    Memory (part number)32GB G.Skill TridentX F3-2400C10Q-32GTX
    Graphics Card #1ASUS Strix GTX 980 Ti OC
    Graphics Card #2ASUS Strix GTX 980 Ti OC (w/ROG Enthusiast 2-way SLI Bridge)
    MonitorASUS ROG Swift PG348Q
    Storage #1(2x) SanDisk Extreme Pro 960GB, (1x) SanDisk Extreme Pro 240GB
    Storage #2(2x) Seagate Barracuda 7200rpm 1TB ST1000DM003 (Raid 0)
    CPU CoolerCRYORIG R1 Ultimate w/Red Heatsink Covers
    CaseCM Storm Trooper w/Custom Side Panel (Window w/(2x) 120mm fans)
    Power SupplyCorsair AX1200i w/Red Braided Cables
    Keyboard SteelSeries Apex M800 Mechanical Gaming
    Mouse SteelSeries Diablo III
    Headset Audio Technica ATHAD500X w/AntLion ModMic 4.0
    Headset/Speakers Logitech X-540 Speakers
    OS Win 7 Ultimate X64 (w/ Virtual XP for older games)
    Network RouterASUS ROG Front Base Dual-Bay Gaming Panel
    Accessory #1 ASUS Blu-Ray Writer BW-16D1HT
    Accessory #2 Seagate 4TB HDD 5900rpm ST4000DM000 (internal - backup & imaging)
    Accessory #3 (9x) case fans Thermaltake Riing + (2x) Lepa Chopper (front bay light effects)
    Ntwlf's Avatar
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    Thanks for sharing AllGamer,

    Pretty cool seeing old tech still up and running with no issues, with the exception of handling present day internet browsing load.

    I have two ABIT "AA8XE" & "FATAL1TY AA8XE" 925XE chipset, LGA775 socketed, motherboard's/pc's still in use running Windows 7. They date back to the late 2004/early 2005 era. I'm currently using the "FATAL1TY" mobo multi-booted (1 of 4 OS's) into Win7 Pro x64 writing this reply, currently still using it daily.
    Last edited by Ntwlf; 05-20-2016 at 08:40 AM.

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