What CPU?

I don't think you'll just be able to change the CPU, at least not to anything that'll last another few years, without also changing the motherboard. And then that means checking if your ram will work with whatever you upgrade to, and you'll need to switch everything over.. .. 

I think you need to do some researching unfortunately, no quick and easy answer. 

Realistically your cheapest upgrade is going to come from keeping your DDR4 RAM and just getting a new CPU/motherboard. I'd look at AMD, you should be able to pick up a Ryzen 5/mobo deal for around £200. Avoid the cheaper deals you see on eBay, they're generally bottom of the pile spec. You also need to see if you have a separate GPU or using the integrated CPU graphics, because that will limit your choices somewhat. 

Personally I'd just search for "SFF PC" on ebay and get the best i5 or i7 refurb from a well known company that you can find in your budget. 

Something like an HP i7 Elitedesk 800 G6 with min 16GB + 240 GB SSD.  They can be had between £300-400.

Dell, Lenovo etc all have their own spin on the same formula. Just check it's 2020+ and it will surely last another 5 years or so.  CPUs aren't really moving on that quickly and your workload is low anyway.

Sorry Im not looking to upgrade my PC, but to replace it with a mini-pc  and am looking at the CPU as a starting point spec wise.

I don't need to power if i7 realistically, but if it would be economical/(expected) working life, I'm happy to do so..

But maybe an old i7 would fuflill my requirement withouth needing to get the latest gen (or just off that) of CPU's

Given the price of DDR5 right now is 250% what it was 12 months ago, I'd suggest an older AMD AM4 chip, some DDR4.  Moar-ish= betterer-ish so 2x8GB will see you through any excel task and a few Chrome tabs between now and 2036 and a matched pair of DIMMs will probably work faster on a dual channel memory slot than trying to match whatever you currently have.

You'll want onboard graphics.

So AMD 5300G 

For your use case, it doesn't seem worth spending cutting edge money in the current market, when if prices come back down again then you could buy yet another new PC with the change. The fact that a 4 year old, bottom tier chip is still >£100 tells you how over inflated the PC market is at the moment.

Posted by: z1ppy

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I don't need to power if i7 realistically, but if it would be economical/(expected) working life, I'm happy to do so..

I5 is fine as well, it's just often there is hardly any price difference between an i7 and i5 refurb so in that case you may as well get the i7.

example:

https://www.ebay.co.uk/itm/168533002435

HP Elite desk from say 3 years ago, like has been suggested.

My 1st Gen Intel core i5  (built the system myself) is still faster than many system available but I stop using it now (still need to transfer files over). Still on Windows 7  😓 

Then I got a HP Elite SFF whatever it is called for free with 8th Gen Intel Core i3 but can only upgrade OS to Windows 10.

Then I bought some spare parts to build 10th Gen Intel i5 which will support Windows 11, but I did not have time to build it so all parts still in box.  Hopefully, I have time to build it in the next two months😬 

Because I needed PC urgently, I just bought a 2nd hand Dell Optiplex 7000 SFF from CEX and it comes with Windows 11 Pro, 12th Gen Intel-i7 16gb RAm and NVME/M.2 500gb SSD (I later upgrade the SSD to 1T Samsung when there was Argos).  Price at around £425.  It is very good so I bought another from CEX as spare for £450, same specs or slightly higher RAM at 32GB.

If I were to buy another one I will go with i5 or i7 13th Gen or 14th Gen.  I think currently Intel CPU is at 15th Gen called Core Ultra series or something.   Reading comments online so far most say that 14th Gen onwards the CPU runs hot but I don't know if that is real etc.

Anyway, check CEX for Dell or whatever brands that have 12th CPU. 

Also if you love listening to music that Dell Optiplex 7000 SFF is shite. i.e. the realtek sound quality is shite and there is no room to install SoundBlaster card in it.  But works fine with low-profile GPU which I have.  It also does not come with WIFI so you need to install that yourself either a low profile card version or one with SDD (but the antenna wire is a pain to find one).  So my current unit has low profile wifi and GPU cards in them.  No more slot for SoundBlaster.  Will buy external sound card to see if music quality will increase.

Therefore, go check CEX.  You might some good deal there.  Oh ya, mine was formerly own by some Ticket booking company (not going to say the name).

Oh ya ... to run Win 11 make sure the CPU is minimum 10th Gen.

Here are some of what is available on CEX at the moment. 

I just looked at everything less than £500 with minimum 10th Gen CPU.  Most are Micro PC which may or may not to be your liking but have a look.

Acer XC-1660/i5-11400/8GB DDR4/1TB HDD/W11/B - £180 (as backup PC so just need to upgrade RAM)

Dell 7020 Micro/i5-14500T/8GB DDR4/256GB SSD/W11/B -£325.00 (need to upgrade RAM and SSD)

Cheers my dears, that’s fantastic & the answers I was looking for & more. Hadn’t considered SFF’s, was fixated on mini’s, but space isn’t an issue. I may even have a (very old) SFF sound blaster card somewhere

If you are also buying 2nd speakers for your PC like Creative T40 Series two (very good speakers) make sure you get the right power supply with output 27V 3A or 27V 1.7A.  Check the power supply before buying.  Otherwise the speakers will not work or the power supply will run hot, just like mine now.  One with undervoltage power supply and the speakers stop working now, while the other has slightly lower out at 20V 2800mA and running hot.