Found a spec sheet for a PCI - ISA bridge that supports DMA...
And then couldn't find anything that used said bridge.
Any ideas at to what would have? Just for the heck of it, I would go and rip one off an old MB just to make a custom bridgeboard.
PDF spec sheet for posterity's sake.
I found details of an AGP-PCI bridge once that let you put AGP cards in a PCI slot. . Was only sold in Japan for a short time. Not many got out into the outside world. There's a guy over at 3DFX zone who managed to snag a couple before they were discontinued.
There's also adapters that let you plug an ISA card into a USB port.
I'd love to get my hands on one of those AGP to PCI adapters... gives better possibilities on an older system 😀
wrote:Found a spec sheet for a PCI - ISA bridge that supports DMA... […]
Found a spec sheet for a PCI - ISA bridge that supports DMA...
And then couldn't find anything that used said bridge.
Any ideas at to what would have? Just for the heck of it, I would go and rip one off an old MB just to make a custom bridgeboard.
PDF spec sheet for posterity's sake.
From the manual of my industrial p4 board:
"The Phoenix ATX features a National Semiconductor PC87200 PCI to ISA Bridge. The PC87200 Enhanced Integrated PCI-to-ISA bridge works with an LPC chipset to provide ISA slot support."
I'm pretty sure that's the chip that was used in the Dell GX110 as well. And any post-440BX Intel chipset board with ISA slots will have something similar.
wrote:I'm pretty sure that's the chip that was used in the Dell GX110 as well. And any post-440BX Intel chipset board with ISA slots will have something similar.
I actually got my computer back last weekend wich is a s370 board, i815 with ISA slot, and I know it must use a bridge chip.
Will take pic later, just got home and I'm tired 🤣
There's something on ebay right now that's unusual. It's an adapter with USB ports that plugs into an AGP slot. I'm not sure under what circumstances you would want your USB card to be plugged in to an AGP slot instead of a PCI slot, but here it is.
http://cgi.ebay.com/HP-Micro-Star-RP5000-PCI- … 3-/320504209855
and another one
http://cgi.ebay.com/HP-Compaq-Powered-USB-Ada … 1-/370336917430
There's something on ebay right now that's unusual. It's an adapter with USB ports that plugs into an AGP slot. I'm not sure under what circumstances you would want your USB card to be plugged in to an AGP slot instead of a PCI slot, but here it is.
It's 12V powered USB for point-of-sale systems. It just uses the AGP slot for power, basically. Notice the little header behind the topmost USB port, you connect that to one of the USB pin-headers on the motherboard.
wrote:There's something on ebay right now that's unusual. It's an adapter with USB ports that plugs into an AGP slot. I'm not sure und […]
There's something on ebay right now that's unusual. It's an adapter with USB ports that plugs into an AGP slot. I'm not sure under what circumstances you would want your USB card to be plugged in to an AGP slot instead of a PCI slot, but here it is.
http://cgi.ebay.com/HP-Micro-Star-RP5000-PCI- … 3-/320504209855
and another one
http://cgi.ebay.com/HP-Compaq-Powered-USB-Ada … 1-/370336917430
Methinks it's using the AGP slot as a 66mhz pci slot 😀.
Why they'd do such a think is a mystery as you said though.
Methinks it's using the AGP slot as a 66mhz pci slot
Read my post above. It does not transfer any data through the AGP slot. That much should be pretty clear just by looking at it... notice how few pins are on the AGP connector.
wrote:Methinks it's using the AGP slot as a 66mhz pci slot
Read my post above. It does not transfer any data through the AGP slot. That much should be pretty clear just by looking at it... notice how few pins are on the AGP connector.
Ah, I have egg on my face now.
That's an interesting approach to adding powered USB. I guess it's beneficial vs an external powered hub as it's less likely to get stolen, and most POS equipment uses whatever integrated graphics come with the system (because come on, how much GPU do you need for that application). So, neato, you learn something every day 😀.
I did a bit more looking, and it appears I was mistaken.
No, it doesn't use the main data bus of the AGP slot, but it looks like it does use the USB pins of the AGP port. I did not previously know that AGP even had USB signals on it, but according to the pin diagram, it does... A4 and B4. Weird. The rest of the connections through the AGP slot seem just to be going to ground.
So, best I can tell with that new bit of knowledge is, two of the USB ports are driven from the motherboard's USB header and the third is run through the AGP slot. The rest of the AGP fingers are just there to prevent ground loops or whatever, and all the power actually comes from the Molex. That makes a bit more sense, but it still strikes me as quite Rube Goldberg-esque.
wrote:I did a bit more looking, and it appears I was mistaken.
No, it doesn't use the main data bus of the AGP slot, but it looks like it does use the USB pins of the AGP port. I did not previously know that AGP even had USB signals on it, but according to the pin diagram, it does... A4 and B4. Weird. The rest of the connections through the AGP slot seem just to be going to ground.
Wow, that's new to me. Did they ever use it in a regular graphics card?
AGP has USB lines in it? Learn something new everyday...
Back on topic I had always assumed that ISA bridge chips that had actual DMA and could channel that many IRQs were extremely rare, I suppose, in actuality, they are not?
