and the power supply. The ribbon cables will clog the airflow so use round cables.
You can buy PCI cards with two IDE ports [support 4 drives]
If your mobo has separate RAID controller that you are not using, and IF it allows ATA drive as well as RAID on those ports that's more.
Many newer power mobos provide for 12 drives when including RAID[that allows ATA or ATAPI] and SATA
after a couple of upgrades i have several large hard drives left over, how many can i put in a single machine?

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