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#1
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Any known issues with Dell computers and ISA bus functionality?
I've got a 16-bit ISA card (part of a specialty piece of data
acquisition equipment) that I know works in several different mainstream motherboards (Soyo, Tyan, Gigabyte, etc). It doesn't function correctly in a computer that I've been asked to test it on: Dell optiplex gx150 manufactured April 2002. This is a desktop tower computer with one 16-bit ISA bus slot that is connected to the motherboard via a side-mounted edgecard connector (as if the ISA slot was designed as an optional add-on component to the motherboard). While debugging this board with a scope and some machine code written and executed from within the DOS debug program, it seems that the motherboard is not correctly honoring the IOCS-16 bus signal being generated by the ISA card. I think it's generating two 8-bit writes in response to a 16-bit I/O write. The IOCS-16 signal seems to be working correctly. Are there any known issues with Dell computers like this and ISA bus functionality? |
#2
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Any known issues with Dell computers and ISA bus functionality?
"PC Guy" wrote in message ...
I've got a 16-bit ISA card (part of a specialty piece of data acquisition equipment) that I know works in several different mainstream motherboards (Soyo, Tyan, Gigabyte, etc). It doesn't function correctly in a computer that I've been asked to test it on: Dell optiplex gx150 manufactured April 2002. This is a desktop tower computer with one 16-bit ISA bus slot that is connected to the motherboard via a side-mounted edgecard connector (as if the ISA slot was designed as an optional add-on component to the motherboard). While debugging this board with a scope and some machine code written and executed from within the DOS debug program, it seems that the motherboard is not correctly honoring the IOCS-16 bus signal being generated by the ISA card. I think it's generating two 8-bit writes in response to a 16-bit I/O write. The IOCS-16 signal seems to be working correctly. Are there any known issues with Dell computers like this and ISA bus functionality? Have you checked for any relevant options in the system bios? Also, does the ISA slot share IRQs or other resources with another slot or onboard device? |
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Any known issues with Dell computers and ISA bus functionality?
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#4
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Any known issues with Dell computers and ISA bus functionality?
"PC Guy" wrote in message ...
wrote: I think it's generating two 8-bit writes in response to a 16-bit I/O write. The IOCS-16 signal seems to be working correctly. Are there any known issues with Dell computers like this and ISA bus functionality? Have you checked for any relevant options in the system bios? What I've encountered in the past with motherboards made from, say, 1996 to maybe 2000 is that BIOS settings that referred to "16-bit wait states" played a role with the some ISA cards I've dealt with in the past. This was also referred to as "16 bit I/O recovery time" with choices like 0, 1, 2, or 3. I haven't seen any such bios settings on motherboards with ISA slots made since 2000 or 2001. With regard to the Dell Optiplex I'm working with right now, there is no such BIOS setting that I can find. I have come across some internet references that Dell might have a "compatibility" mode option in the BIOS which I'll look for tommorrow. This is a longshot, but also check for a jumper on the motherboard. Also, does the ISA slot share IRQs or other resources with another slot or onboard device? I would expect that the IRQ's available on the ISA slot are shared (or not?) in a manner that is typical with conventional motherboards with the normal compliement of ISA/PCI/AGP slots. However, the ISA board in question is a pure I/O device only - it does not use IRQ's or DMA's. All reads and writes are 16 bit. When I boot the computer into Windows XP, the hardware manager device I/O list does not show any devices using the I/O address range that the board is using. The ISA card is using relatively modern programmable logic chips for all operational aspects (including bus decode) so perhaps the IOCS-16 signal that it is generating is "too fast" or too short for the Dell to see? Well, the fact that XP doesn't list a given I/O range as being in use, doesn't necesarily mean it's unused. I've run into problems installing legacy cards at various addresses (e.g. Adaptec scsi cards with a default of 140h, audio cards at 350 and 250h, even joysticks at 200h, and ran into conflicts even though Device Manager claimed these addresses weren't in use. Just out of curiosity, what range does your card use? |
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Any known issues with Dell computers and ISA bus functionality?
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#6
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Any known issues with Dell computers and ISA bus functionality?
PC Guy wrote:
wrote: I would expect that all system devices to be pnp compliant and to be present in the device manager list. Ah, but this is a Dell you're talking about, I wouldn't expect anything in it to necessarily be compliant in the way you may understand it. I tried to install an OEM CD burner in a fairly modern Dell recently. Having changed every possible jumper, setting and cable I could think of, with no success, I gave up, Put the burner in a generic PC and it worked first time. But I bet if I bought a burner from Dell it would magically work. :-) SteveH |
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Any known issues with Dell computers and ISA bus functionality?
"PC Guy" wrote...
Also, does the ISA slot share IRQs or other resources with another slot or onboard device? I would expect that the IRQ's available on the ISA slot are shared (or not?) in a manner that is typical with conventional motherboards with the normal compliement of ISA/PCI/AGP slots. That's one place where ISA and PCI are different -- no shared IRQs allowed on ISA. However, the ISA board in question is a pure I/O device only - it does not use IRQ's or DMA's. All reads and writes are 16 bit. When I boot the computer into Windows XP, the hardware manager device I/O list does not show any devices using the I/O address range that the board is using. ISA modem cards, for example, usually had jumperable IRQ settings. Another possible quirk is that it will work in one slot, but not another. I recall having problems on at least one board with the slot closest to the AGP slot, and have solved otherwise indecipherable problems in the past by merely swapping ISA slots. |
#8
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Any known issues with Dell computers and ISA bus functionality?
John Weiss wrote:
Another possible quirk is that it will work in one slot, but not another. This dell only has a single ISA slot, mounted on it's own small strip of PC board with a bit of circuitry, connected to the main motherboard via a side-mounted high-density, low profile edgecard connector. The bit of circuitry on the board looks to include a PCI-ISA bridge chip. I recall having problems on at least one board with the slot closest to the AGP slot, and have solved otherwise indecipherable problems in the past by merely swapping ISA slots. I've had problems in the past with the functionality of some PCI boards plugged into the PCI slot closest to the AGP slot. I've never had any similar ISA-board functionality issues like that, and have never seen a motherboard with ISA slots immediately adjacent to an AGP slot without there being PCI slots between them. |
#9
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Any known issues with Dell computers and ISA bus functionality?
"John Weiss" wrote in message news:45ed7200@kcnews03...
"PC Guy" wrote... Also, does the ISA slot share IRQs or other resources with another slot or onboard device? I would expect that the IRQ's available on the ISA slot are shared (or not?) in a manner that is typical with conventional motherboards with the normal compliement of ISA/PCI/AGP slots. That's one place where ISA and PCI are different -- no shared IRQs allowed on ISA. That's not quite correct. Multiple ISA devices cannot share an IRQ, however on boards that have both ISA and PCI slots it's common for the ISA to share with a PCI slot. E.g. my Abit BF6 has 5 PCI/1 ISA, and the ISA shares with one of the PCI slots. |
#10
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Any known issues with Dell computers and ISA bus functionality?
Further to my original post, here is more information regarding this
ISA problem on the Dell computer. This was a Dell Optiplex GX150 manufactured in April 2002. It has an Intel Pentium-3, 1Ghz clock speed, 256 mb of system memory. The video adapter and all other interface devices are integrated onto the motherboard. The motherboard has several available expansion slots (AGP, PCI, and 1 ISA) all of which were available (no pre-installed card installed in any of them). The ISA slot was built into it's own separate PC board that was connected to the main motherboard with a high-density side-mounted connector. On this separate PC board was a National Semiconductor PCI-to-ISA bridge (PC87200) which translates I/O and data signals and commands from the motherboard to the ISA slot. This National Instruments chip seems to be a first-generation version PCI-to-ISA bridge introduced in early 1999 that allowed PC and motherboard makers to add ISA slots to their systems and still be classified as PC99 compliant. Curiously, National Instruments makes no information available on it's web site about this chip (no spec sheets, no white papers, etc). The only reference to this chip is in this March 1999 press release: NATIONAL SEMICONDUCTOR ANNOUNCES PCI-TO-ISA BRIDGE FOR NEW PC99-COMPLIANT SYSTEMS PC87200 Enables PC Manufacturers to Add ISA Slots to Their PCI Systems http://www.national.com/news/item/0,1735,361,00.html My previous experience with ISA instability or non-functionality were usually solved on older motherboards by changing the 16-bit I/O wait-state setting in the system BIOS, but there was no such setting on this Dell Optiplex. The Dell had bios revision 09, and it was updated to the apparent last version made available by Dell (version 11) which made no difference. ISA bus signals were investigated using an oscilloscope while low-level data commands (I/O reads and writes) were performed to addresses being decoded by a 16-bit data acquisition ISA card. While the addresses were being decoded correctly, all transactions were being performed in 8-bit mode instead of 16-bit mode. When performing 16-bit I/O reads or writes on the ISA bus to even (not odd) addresses, the bus controller can either perform this as a single transaction, or it can perform 2 sequential 8-bit transactions. ISA bus specifications dictate that the target ISA card controls this transaction (16-bit or 8-bit) by asserting the IOCS-16 line if the card is indeed capable of performing 16-bit transactions. The ISA card was asserting the IOCS-16 line correctly (this line is normally in the high state and is active-low when asserted, for the duration of the address decode which was observed to be 500 nanoseconds). However, the Dell Optiplex, and presumably specifically the National Semiconductor PC87200 chip, does not seem to honor the state of the IOCS-16 line and instead performs 16-bit I/O reads and writes as two sequential 8-bit operations. Perhaps this was a defect for this specific Dell computer, but there are plenty of other situations where these mass-marketed computers have shown to cut corners physically, electrically, and compatability-wise with generally recognized standards and components. |
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