Good info. I wonder what that adapter is doing to generate the needed 12V standby (ATX standby is only 5V).
All the more reason to avoid it. Power supplies are one of the first things to go bad (alongside hard disks, but at least they're all standard). Those Precisions have some modular wiring looms in them but the board connections are all standard, on later Precisions T3600/5600, etc. they made them proprietary again, to do with dual-redundant PSUs but I think we all know why they did. I wish they hadn't done this. I don't like adapters as you've probably seen with people building bad mining rigs or using overpowered GPUs, it doesn't take a lot to melt a cable.
https://www.ebay.co.uk/p/ATX-24pin-to-8pin-Power-Supply-Cable-for-Dell-Optiplex-3020-7020-9020-T1700/557044756 dell 24 pin to 8 pin adapter https://www.dell.com/community/Desktops-General-Read-Only/Upgrading-GPU-and-PSU-for-Optiplex-9020-baffled-by-8-pin/td-p/4434910 not sure if the psu would actually fit inside tho as some after markets ones are slightly different sizes
https://www.dell.com/support/manuals/uk/en/ukdhs1/optiplex-9020-desktop/opt9020mtom-v2/specifications?guid=guid-c5123572-8b34-4085-88ec-8633c66143ac〈=en-us "Power connector: Mini-Tower, Small Form Factor one 8-pin. one 4-pin, one 6-pin, connector" https://www.rakuten.com/shop/pricerightcomputers/product/2dv1ufbmj/ Good luck attaching an ATX power supply to that! Looks like a 12V only PSU. 3.3V & 5V are thus generated on the motherboard, then passed out to the devices (via the 6 [actually 5] pin connector) There may well be variants of the Dell 9020 mini-tower that don't use this proprietary power layout, but all the examples I've found use the above. Moreover ITZOO make no claim as to the precise configuration of what they're selling.
Sorry, wrong thread, thought it was a toaster. :o