Will this work? I found a cheap serial port card I need for a POS receipt printer but I'm not sure if the computer has a PCI Express x1 slot.
For sure it has a PCI slot though so I'm wondering if I can pop it in
Will this work? I found a cheap serial port card I need for a POS receipt printer but I'm not sure if the computer has a PCI Express x1 slot.
For sure it has a PCI slot though so I'm wondering if I can pop it in

No, they have different sized slots, and their buses differ.
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Rule of thumb tends to be you can put a 'smaller' PCIe card into a larger slot - so a x1 will fit in an x16.
If you're trying to put in an pci e x1 card into a pci slot, adaptors exist - these use chips that were originally meant for using GPUs designed for pci-e on PCI. Most systems should have at least one x1 card slot, unless this is something like mini ITX
However many modern systems do still have serial port headers. Its worth checking if you have one, getting a suitable adaptor and using that instead.
You can place a PCIe 1x card into any available PCIe slot and it will work -- even if the slot is longer than the card.
You can NOT plug it into the PCI slot however.