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Thread: Everex ev-18108 motherboard

  1. #21
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    Quote Originally Posted by RiP2 View Post
    3. The system memory should be at least 1MB. Maybe it's for the 512/640K base memory but it has an option for it in the BIOS.
    There is no memory installed on that motherboard, you need the proprietary memory daughterboard that fits in the ISA looking slot on the bottom middle of the motherboard, under the CPU cache chips. Unless you have this daughterboard, the motherboard is useless.

    Quote Originally Posted by RiP2 View Post
    5. Won't 80MHz crystal conflict with the ISA bus speed? With 66MHz, ISA works at 33/4=8.25MHz
    There was never a defined clock speed for the ISA bus. 808x - 80286 motherboards generally ran the ISA bus at the same speed as the CPU, which lead to a wide range of clocks from 4.77 - 25 MHz. The faster clocks often caused compatibility issues with cards or software that wasn't designed to run so fast. Once you got beyond 8-10 MHz, things got dicey. 386 and onwards had several methods of generating the ISA bus clock. You could run a divider off the CPU clock or have a secondary crystal for the bus. Even later 486 and Pentiums sometimes ran a divider off the PCI bus clock with a 1/3 or 1/4 option.

    I suspect that second 14.31818 MHz crystal may be responsible for the ISA bus clock, by using a 1/2 divider, you get a ~7.16 MHz clock.

  2. #22

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    Quote Originally Posted by modem7 View Post
    The battery connector looks like the standard one used for a 6V lithium battery. If so, the options at [here], for an IBM AT, should be applicable.

    From an infoWord magazine, "InSTEP" is a trademark of Everex.
    At [here], an "instep board" is shown in the Connections section, with the board appearing to be a form of CPU upgrade.
    Do an Internet search using: everex instep 486
    Are you sure about 6-Volt? I have seen 3.6V too, and not sure if rechargeable or not:



    Thanks for InSTEP info.

    Quote Originally Posted by GiGaBiTe View Post
    There is no memory installed on that motherboard, you need the proprietary memory daughterboard that fits in the ISA looking slot on the bottom middle of the motherboard, under the CPU cache chips. Unless you have this daughterboard, the motherboard is useless.


    There was never a defined clock speed for the ISA bus. 808x - 80286 motherboards generally ran the ISA bus at the same speed as the CPU, which lead to a wide range of clocks from 4.77 - 25 MHz. The faster clocks often caused compatibility issues with cards or software that wasn't designed to run so fast. Once you got beyond 8-10 MHz, things got dicey. 386 and onwards had several methods of generating the ISA bus clock. You could run a divider off the CPU clock or have a secondary crystal for the bus. Even later 486 and Pentiums sometimes ran a divider off the PCI bus clock with a 1/3 or 1/4 option.

    I suspect that second 14.31818 MHz crystal may be responsible for the ISA bus clock, by using a 1/2 divider, you get a ~7.16 MHz clock.
    I have the memory card, I said before that it's all working fine. It has a beautiful OLED-like front panel too

    I was thinking about the 14.31818 MHz crystal too but since I remember, the BIOS could set the ISA bus speed as CPU clock/4 or CPU clock/3
    I'll check it again to be sure.

  3. #23
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    Quote Originally Posted by RiP2 View Post
    Are you sure about 6-Volt?
    Definitely not. That is why I wrote, "If so". Unfortunately, no one has put their hand up and said, "I have that model of motherboard and the battery used is xxxxxx." or "At yyyyyy is what Everex indicates is required for that connector on that model of motherboard." So, everything else that you hear is an opinion. For all we know, for the subject motherboard, Everex require a battery module that contains an isolation diode.

    On some motherboards, a 3.6V battery is inadequate/borderline (an example being the IBM AT), or will not last very long. There are some motherboards where the user's manual indicates the use of a 4.5V battery.

    If you have the ability, draw a circuit diagram of the associated circuitry, and someone here can then provide a very informed opinion.

    Quote Originally Posted by RiP2 View Post
    I have seen 3.6V too, and not sure if rechargeable or not:
    The 3.6V battery that you pictured is lithium (not lithium-ion), and accordingly, is not rechargeable. That example was made in Feb 1996; 23 years ago. New, it would have measured about 3.7V. Today, it will be substantially less.

  4. #24
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    Because the subject of 'CMOS setup' batteries appears periodically, I created an information web page at [here].

  5. #25
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    Quote Originally Posted by RiP2 View Post
    I have the memory card, I said before that it's all working fine. It has a beautiful OLED-like front panel too

    I was thinking about the 14.31818 MHz crystal too but since I remember, the BIOS could set the ISA bus speed as CPU clock/4 or CPU clock/3
    I'll check it again to be sure.

    The 14.3818 crystal is there to provide a spec-required signal on the ISA bus--and also quite likely to clock the 8254 counter-timer. You don't want to fool with that.

  6. #26

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    Quote Originally Posted by Chuck(G) View Post
    The 14.3818 crystal is there to provide a spec-required signal on the ISA bus--and also quite likely to clock the 8254 counter-timer. You don't want to fool with that.
    Well, I replaced the 66MHz crystal with 80MHz and it worked fine. Now the CPU works at 40MHz, 20% faster.

    But I'm still worry about the ISA bus speed if now it's working at 10MHz or not:



    I have also measured the voltage of external battery connector and it's 4.8V but not sure what kind of battery I should use for it, 3.6/4.5/6-volt

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