The so-called "RAID key" or "PERC enabler" (part number 8286R) for the Dell Poweredge 2450 rack-mount server earns its "crap" status by virtue of being a complete and utter fucking rip-off.
What is it? It's a little gizmo that plugs into the motherboard of a Poweredge 2450 to activate the on-board hardware RAID controller. Without it you can only do software RAID. Someone sent me one of these servers to set up; it didn't have the gizmo, so I ordered one.
The first obstacle I had to overcome was the piss bloody awkward website design that prevails among Dell server parts sellers. They have a really fucked up idea of how to attract business. Could I order the gizmo off the websites? Could I arse. The website of the least obstructive place said they had some in stock but wouldn't even tell me the price, let alone let me order it. What I had to do was: Register on the website, wait for the confirmation email, log in, put the part number into a web form to request the price, wait for the email with the price in - which was generated by a human, not by a database lookup, so I had to wait until the next day - and then put a cheque in the post. What a bloody carry on. If I'd wanted the thing for myself instead of for a job I would have said "fuck this, I'll do without it". And that was the simplest - some of the other places would have involved even more arsing around. Do Dell put their parts distributors through some kind of "how to piss customers off and make them go somewhere else" course?
Having gone through all this crap, how much did I have to pay? Eighty-two pounds. What did I get for it? A little PCB with a 10-pin DIP header socket, a few SMD resistors and capacitors, and a 24C02 serial EEPROM chip. A chip that costs pennies. The kind of tiny chip that you find in the corner of a DIMM, hiding from all the nasty big chips - a DIMM that doesn't cost a quarter of what this thing cost and has a bunch of much more expensive (as chips go) RAM chips on it.
Well, I had to find out what was going on here. For that price, there had to be some kind of enabling code stored in the EEPROM. So I dumped it. The fucking thing was blank. Every location read FF - it was straight as supplied from the chip factory. I'd just fucking paid eighty-two fucking quid for a fucking blank 24C02.
So I decided it would be a good idea to help out anyone else who wants a Dell 2450 Poweredge RAID key. I traced out the extremely simple circuit, ignoring the network of jumper links that aren't actually connected to anything, and making an educated guess at the values of the capacitors - they're only decouplers, so they're not critical, and indeed I see no reason why the resistors should not be replaced with direct connections.
There's no need for a PCB for such a simple circuit - the 24C02 doesn't operate at any great speed, so it could easily be knocked up on a piece of Veroboard with the strips running vertically. The dimensions (in millimetres) of the real thing, and the orientation of the 0.1" pitch DIP header socket, are shown in this sketch:
The dimensions of the projection with the DIP header socket on it are fairly critical, so that the key fits properly into the receptacle/plug thing on the motherboard. The tab part with the chip on is not critical. The original has two holes in the tab, but they don't engage with anything, so I haven't bothered to draw them.
An unrelated point when activating the RAID is that as well as the key the RAID controller needs a 64MB DIMM, and it is fussy as fuck about what kind of DIMM you give it. Dell's installation instructions say you must use "an unbuffered DIMM, rated to run at 100MHz". No problem, I thought, got plenty of those lying about. But none of the bloody things worked. They worked plugged into random PCs, but the RAID controller wouldn't believe they existed. As a final desperate experiment I borrowed the DIMM out of the Intel RAID controller in one of my working machines... bingo, it worked. The successful DIMM was a Kingston KVR100X72C2/64 which uses Samsung K4S640832F-TC75 DRAM chips.
That Intel RAID controller was just as fussy about its memory as the Dell one is; the KVR100X72C2/64 was not common when I set that machine up, and it's even harder to find now. Which is an arse. Both the Intel and Dell RAID controllers have an Intel 80960 RISC CPU, but nothing else in common, so perhaps that is the cause of the fussiness.
