RIHAHN.COM

Month: August 2023

  • Change of plan

    A couple of years ago I early-adopted a cloud-based computing platform called “Shadow“.

    Shadow is interesting because it’s not really a cloud-based gaming platform, it just pretends to be one really well… It’s more aimed at creating dedicated remote-access high-performance computing platforms. Think of it like a modern, low-latency terminal services / RDP setup for people using 3d modelers and video production pipelines.

    This has two main effects for the end-user; there is no pre-installed library of games so you’re free to install literally anything you want, and because of this it’s a little bit more involved to do some gaming than something like Geforce Now.

    Unfortunately the first iteration of Shadow didn’t fare well financially and when they filed for bankruptcy I bailed. But the company was purchased and they’re trying again – so I signed back up.

    What this means for me is I now have access to a server in Utah with a quarter of an AMD Epyc 7543P CPU (8 cores), 28 gigs of ram, 512G of server-class storage, a dedicated RTX A4500 video card, and a gigabit network connection…

    Of course the first thing I did was load the Secondlife client “Firestorm” on it to see how it would handle virtual world graphical sludge…

    Around 100fps at 4K ultra-settings pretty much everywhere with 4 avatars. It’ll hold well over 50fps at those settings with ~40 avatars around in really hard to render places as well, so running vsync at 30Hz to my huge OLED screen is totally doable. And if I turn off shadows it’ll jump back up to 80-90fps in those situations letting me bump up the monitor to 60Hz.

    And while it’s doing this, it’s in a datacenter using someone else’s power and cooling.

    There is a cost for this, of course, and it’s about $50 a month ($40 a month if you pay in 6-month chunks) – which is about what my old Windows workstation with similar specs cost in electricity per month… So for me it works out.

    Now, this sort of thing only really works for the kinds of games I enjoy; things that aren’t horribly twitchy like turn-based RPGs, simulations, or Secondlife. Something like a competitive shooter where 144fps and sub-10ms peripheral response time is the difference between life and death isn’t a good use case for Shadow.

    Don’t get me wrong though, on the desktop and in something like Secondlife you don’t even notice you’re on a remote system. Average desktop granularity is 28-30ms on a system sitting right in front of you, and Shadow on my networks at home and work seems to average about 35-38ms.

    Anyway, with a couple of days of testing from the Mac Pro 5,1, my i3 Macbook Air, my M2 Max laptop, and even my iPhone (yes there’s a smartphone client for Shadow), I decided to change things up computer-wise.

    Going forward I’ll be using the 2013 trashcan at home and will move the 2012 Mac Pro to the office.

    The reason for this is basically utility costs… The 2013 Mac Pro uses far less wattage and therefore makes far less heat than the 2012 Mac Pro does. The 2013 is also much, much quieter than the 2012 because the 2012 needs nine fans to compensate for all the heat.

    I’d initially decided on using the 2012 cheese grater at home because I could upgrade the GPU in it for gaming, but with Shadow this is no longer a point of contention. At work I can leverage commercial power and cooling in a three story building full of computers, so the 2012’s thirst for electricity and air-conditioning isn’t a big deal here.

    There’s also the fact that while the 2012 will run MacOS Monterey with some fiddling, it isn’t without some hassles and loss of features. The 2013 natively supports Monterey so all of the OS features just work… Which is a ‘nice to have’ on a personal system you’re using every day.

    I guess can also skip my yearly tithe to Parallels being as I have ready access to a Windows machine with Shadow… So no need for a virtual Windows instance on every computer I use, and another savings.

    Listening to "Fallout" by Mantus

  • Update

    It’s been about a week now of using a 2011 computer in 2023, and things are still going well. The only real noticeable difference between decades is that the Mac Pro takes a second or two longer to open an application – and some of the fancy “AI” things in Photoshop take 10 seconds or so to process.

    The only real “game” I play is Secondlife (SL for short), and the 2012 Mac Pro does okay with that as well. Though I also own the new Baldur’s Gate III game, but it won’t be out for Mac until the 6th… But I expect the Mac Pro will do okay with that as well.

    As for Secondlife, it is, well, old – so it’s not exactly a speed demon even on pinnacle hardware. The client that is used to connect to the service is generally single-threaded and therefore mostly CPU-bound. And in SL the entire visible world can be changed on a whim, with user generated content, and this makes for a decidedly unoptimized render pipeline. This means that even on things like my old Windows workstation (Xeon 6312U / Nvidia 3090) I would generally get 20-30 FPS at “ultra” settings, in a 4K window, in busy areas with lots of people in them.

    The Mac Pro gets 20-30 FPS in the same areas with the same number of people, but with slightly reduced graphics settings and a 1440p window size – which isn’t bad for what it is.

    You may have noticed that I mentioned ‘fancy AI things in Photoshop’ up above; yes – I paid for another year of Creative Cloud.

    Fortunately, I’ve already made that money back… See, I sell some stuff I make on the Secondlife marketplace and I also completed some custom texture work for a couple of folks. And this netted enough to cover another year of Adobe Mafia protection.

    Basically I work to afford the tools I use to to do work to afford the tools… But with the cost covered I was able to spend a few days working on some stuff for myself, which was fun.

    Other than that, everything is mostly okay – or at least as okay as is possible here in 2023. Everything is crazy expensive so I don’t really leave the house save to get supplies, which means my car isn’t getting very many miles put on it and all of my entertainment is on the computer… I have managed to catch a few new(er) movies though, and the other day I binge-watched the entire second season of “Strange New Worlds” which wasn’t bad.

    Listening to "Lightbeams" by MJ Cook

  • And scene…

    It’s been quite the journey to get to this point; sketchy mining cards, shipping complications, undocumented third-party utilities, and a distinct lack of modern-ish Windows hardware at my disposal.

    That latter kept me at the office until 8pm last night as I tried valiantly to reflash the new RX 6600 XT with random scraps of PC hardware running Windows 8.1. But I kept getting a GDI32.dll error with the open sorcery VBIOS write tool and eventually had to stop for the night.

    Bright and early this morning I started the update process to Win10, assuming that would probably fix it, and got to deal with the usual spate of Windows-isms… Like this one:

    Yes, that really is a Razer “driver” attempting to install while Win10 is still installing…

    But, after a half dozen restarts to do yet more updates that totaled about an hour of downtime, I was finally able to flash the new RX 6600 XT for use in the 2012 Mac Pro.

    About an hour after this FedEx dropped off the new CPU tray in the gravel next to my garage, so I came home, unboxed the tray, loaded CPUs and ram, and shoved everything into the 2012 Mac Pro…

    The installation of the CPU tray and video card were literally the least effort part of this whole ordeal – and the Mac Pro fired right up with the new hardware.

    And with that I’m free to sell off my MacBook Pro M2 Max…

    To be honest? I’m not sure I’ll miss the laptop. The 11 year old machine I’m daily driving now is actually more powerful where the rubber meets the road; mostly because I don’t use any of the handful of apps tailored to use the fancy bits of Apple Silicon.

    Apple Silicon does definitely win when it comes to power efficiency though, and I expect the Mac Pro will wind up costing me a few bucks each month in electricity… But I think it’ll be worth it.

    Listening to "Rabbit Hole Chasing You (2023 Live)" by morgan willis

  • Life in the crypto-mines

    The RX 6600 XT I ordered off of Amazon for the 2012 Mac Pro arrived last night, and a few minutes later I had it installed in the PC I prepped for video card flashing… I use an older Intel Desktop Board for this because of the amount of info it gives when messing with hardware…

    That’s an old HD 6970 I was testing…

    The board has two sets of firmware in case you mangle one while fiddling, has power and reset right on the board because it’s test hardware, shows the boot process on the green 7-segments next to the ram, and the row of green LEDs at the bottom show the status of major components (the one in the middle shows the status of the video card), and most importantly it has an LED skull with blinking eyes for hard drive read/write!

    Anyway, the machine wouldn’t boot with the RX 6600 XT in the system. Everything halted with post code EB which is where the system looks for video BIOS / firmware on the bus – and it found nothing.

    This usually means the card has been reflashed with mining firmware, which doesn’t require video output so it’s disabled. In fact anything not associated with compute is usually disabled for crypto mining.

    Crypto mining essentially turns electricity and video cards into imaginary money, so getting a used mining card is generally more miss than hit as it’s been run harder than it was designed to, 24 / 7, until it either had a problem or was replaced with something faster.

    Now, while I could most likely fix this card by flashing the original firmware back onto it, the fact that the seller clearly didn’t even test it before slapping it into a used static bag and chucking it into a box didn’t leave me with much confidence.

    So I just requested a refund, put the card back in the used static bag and the box, and headed over to the local UPS store to send it back… The UPS Store closes at 19:00, and while I got there at 18:34 they were already closed for the day, unfortunately.

    So I’ll send it back after work today.

    And I ordered another RX 6600 XT from Amazon. A brand new, never been used one… Of course it was a hundred bucks more than the used mining card – but at least it will work.

    Hopefully.

    Nothing is guaranteed with Amazon… I’ll probably get some cheap Chinese knockoff card. :/

    Listening to "Taste Like Venom" by GUNSHIP

  • 20 years…

    Back on the 5th I quietly celebrated twenty years of this journal.

    I started this ongoing chronicle of my so called life on August 5th 2003 over on LiveJournal, and I had planned to post something about in on the day – but things were busy with running all over Denver to pick up the MacPro and whatnot.

    Oddly enough, I set up this domain in August of ’99 – so the domain has been running for 24 years now as well… I should plan some sort of 25th year anniversary thing for next year.

    In other news I’ve finished moving into the 2012 Mac Pro, which as of this afternoon is acting as my daily driver in preparation for selling my M2 Max MacBook Pro.

    It was a bit weird to disconnect everything from my laptop, unplug the power adapter, and set it all aside…

    The 2012 is still running on a single 6-core Xeon, but that should be fixed some time next week once the new tray arrives and I get a chance to fully populate it with two top-end 6-core Xeons and 128gigs of ram… The ram will come from my big box o’ server ram that a friend sent me, because all of the servers at his datacenter that have been replaced used the same DDR3 ECC as the 2012 – so the memory upgrade will be free…

    About seven pounds of 8 and 16 gig DDR3 ECC sticks…

    But everything else has been updated; macOS Monterey, OWC 1TB Accelsior 1M2 M.2 PCIe card, USB 3.1 / USB-C PCIe card, and an 8gig Radeon RX 580 video card.

    The RX 580 is also temporary… I got a really good deal on it – $80 with cables! – but I have a Radeon RX 6600 XT on the way as well.

    I have been pleasantly surprised at how well this machine runs. It’s an 11 year old computer I got for free with an $80 six year old video card in it and about $100 in new parts – and it does day-to-day stuff pretty much on-par with my $4000 M2 Max MacBook Pro.

    It’s a bit slower in 3D things, like I’m doing good right now to pull 15fps in busy areas of SecondLife where the M2 Max will do 25fps – but the new card, which is about 2x faster in pretty much everything, should fix that.

    The ‘secret sauce’ to getting this machine on-par with a $6000 2019 Mac Pro boiled down to massaging the system’s firmware a bit, creating a custom EFI boot loader, and once the new video card gets here, fixing a bug in its firmware… Once I took care of those few things, macOS Monterey – which is last year’s OS – runs just fine on it.

    Like I mentioned in the previous post; it’s not that these fancy new Apple operating systems can’t run on this machine – it’s that Apple really doesn’t want them to.

    Listening to "Inhale" by New Arcades

  • MacPro 5,1 – round two

    I got a chance to mess with the cheese grater a bit last night in my ongoing attempts to make it a daily driver.

    See, here at work I have a potential client who wants to test on an M2 Max laptop, and we don’t really keep $3200 laptops just laying around for testing – so they’re okay with us purchasing one, doing the testing, and then just sending it to them after the project.

    I happen to have an M2 Max laptop, so I’m seeing this as an opportunity to make a quick $3200 which will offset Bidenomics a bit. And afterward I’ll just use the cheese grater as my personal machine until the economy gets better.

    Sure, the 5,1 is eleven years old at this point, but there’s a reason they were $3000 back in the day – they have an amazing industrial design and used a lot of bleeding edge technology for 2012, so they were quite a bit ahead of their PC relatives at the time…

    That and technology has stagnated a bit in the last decade… Sure, things are smaller and faster, but in the ways that count all that speed is generally wasted; the OS has become bigger, more boated, and slower and most of the SPEEEEED stuff in hardware is just marketing.

    For example, PCIe 4.0 is all the rage and yes, it’s mindblowingly fast – so fast in fact that high-end video cards – the ones that cost like a thousand bucks – only use 8 lanes in the PCIe x16 slot they sit in. New CPUs are pretty incredible, and M.2 storage is stupidfast – so fast that the processors and drives spend 50-75 percent of their time idle because there’s just no real need for that kind of speed on the average user’s desktop.

    And this is a problem if you’re a company that makes their money off of hardware sales, so over the last decade there’s been a marked increase in ‘planned obsolescence’ – where the hardware is artificially limited or the software is specifically instructed to stop supporting things to drive sales.

    Apple does this a lot more than companies on the PC side of things, mostly because Apple is a hardware company. If no one bought a new computer for over a decade, Apple wouldn’t be a trillion dollar company.

    So the MacPro 5,1 and MacOS in general has a lot of little time-bombs in them that artificially age the hardware, but we can fix this with some hackery… And what this means is that with a little massaging, the MacPro 5,1 can still hold its own as a home computer.

    Some of this massaging requires some pretty in-depth fiddling with the machine’s internals, like recoding the boot rom, reprogramming the EFI, and hacking the power supply… Not something the average user is willing to do, but stuff I do before breakfast.

    Literally. This morning I was pushing some changes to the EFI on the 5,1 before I made breakfast…

    Anyway.

    The biggest issues with using the 5,1 as a daily driver are:

    • Apple dropped OS support for it after Mojave (MacOS 10.14). Mojave came out in 2018 and was EoL’d in 2021.
    • Doesn’t understand things like NVME without a boot rom update from Apple.
    • Can only use certain video cards for certain OS versions because Apple bakes the drivers into each OS release. Was also a transition model between OpenGL and Metal, so Mojave won’t even install without a video card upgrade that most likely won’t show preboot graphics.
    • Uses 2012 peripheral technology like PCIe 2.0, USB 2.0, and Firewire 800.
    • Uses 2012 server CPUs that are more dump truck than race car.

    The last two aren’t really issues outside of “speed bias”. By this I mean that, yes, PCIe 2.0 is a smaller number than PCIe 4.0 and decade old Xeon processors don’t have big numbers like “13700” after their names – but as mentioned above, this isn’t really as big of a deal as hardware manufacturers would like you to think.

    PCIe 4.0 is really fast, but ‘big numbers’ don’t tell the whole story… For example, here’s a quick video showing what the real-world difference is between PCIe 1.0, 2.0, 3.0, and 4.0 is using the same higher-end video card:

    Neat huh? This is the reality that exists outside of synthetic benchmarks.

    On the CPU side of things, the most installed CPU on the planet as of this post is the 2021 Ryzen 5 5600X – and it’s about 50% faster than the X5690 Xeon’s in the 5,1 in a CPU benchmark – though the 5,1 has two CPUs…

    If you need to do some work, the Xeon’s still hold their own. But this is again a benchmark and not a real slice-of-life for the average user. For all intents and purposes the average user will be hard pressed to spot the difference between these two CPUs on the desktop… And if you do notice, the delta will be a few milliseconds at worst.

    The other items on the list above can be fixed with boot rom / EFI tweaks that fool newer MacOS versions into continuing to support the 5,1. Even the baked-in drivers can be overcome by injecting them into other OS versions.

    And Apple even threw all of the 5,1 owners a bone by releasing a new boot rom (144.0.0.0) in 2019 that taught the old dog how to boot from NVME! Though that was probably a slight apology for both the trashcan MacPro and the lunatic pricing of the 2019 MacPro (a $6000 base model!?)…

    Now I’m not saying the 5,1 is the ultimate machine by any stretch, and in a couple more years it will probably be just another relic of a bygone computer era – but until then, like a classic car, it’s a perfectly serviceable daily-driver as long as you don’t mind rolling up your sleeves and getting a little dirty under the hood.

    In the end, my 5,1 will have two X5690 6-core Xeons, 128gigs of DDR3 ram, DVD and blu-ray burners, 1.2TB Intel 750 NVME boot drive, USB3, and an ATI RX 6600 XT video card… I definitely won’t be hurting for a few years until I move to whatever the new hotness Mac is in 2025.

    Listening to "Never Surrender" by Triumph

  • There is no saving throw versus the plot device

    Ever get the feeling there is some sort of diabolical Wizard of Oz chuckling quietly to himself as he says “watch this!” and presses a button to make your day much worse than it has to be?

    I’m pretty certain this is how it works – and when I find the guy pushing my buttons there is gonna be such a reckoning. 🙂

    There are patterns to this button pressing though, you just have to watch for them and make note when they occur so you can avoid them and thumb your nose at your personal tormenter on occasion… And yesterday I discovered a new pattern.

    See, my daily driver is a collector’s item – the literal last of the big Detroit V8 sedans – so I’m extremely careful with what the weather looks like when I leave the garage, what traffic looks like where I’m going, and where I park when I get there.

    And thanks to this level of caution I’ve only been narrowly caught in some of Colorado’s routine hail once…

    What happened was that my roommate needed a ride to pick up his truck from the dealership where he had some work done. The weather looked bad, but he was insistent – and on the way back from dropping him off it started hailing… I managed to duck into a gas station just as it started and sloooowly filled my tank until the storm passed.

    So one near miss with the hail… Well, that was until yesterday…

    Yesterday afternoon my roommate once again needed a ride because his truck was out of commission… He needed to swap out the tensioner pulley he’d purchased earlier in the day for one that actually fit his truck, and I’m more than happy to help out – even if it did look a bit like rain. But the weather app on my phone said everything was fine – so off we went to Parker.

    And here’s what happened halfway between Centennial and Parker…

    I turned off the car to wait it out, and that’s when the video stops – it got a bit worse before it let up, and some of the hail got to pingpong ball size…

    Right as I ducked into the parking spot is also about the time the severe weather alert appeared on my phone… It’s called a forecast guys, not an after the factcast…

    Anyway, I once again got lucky and found a spot to hide out from the worst of it, but this time I managed to pick up a few very minor dents… I can fix those though, easy enough – but the hail happened exactly as if someone pressed a button. It went from windows down and enjoying the drive to Hail-Apocalypse in seconds.

    And back to those patterns I mentioned: the pattern here seems to be that if my roommate’s truck is out of commission for any reason and he needs a ride to deal with it – say no. 😀

    Listening to "Modern Love" by KRISTINE

  • Cheese Grater…

    You know how I mentioned that I was pondering picking up a 2012 Mac Pro when I tripped over the 2013 Trashcan Mac Pro – but for various reasons decided not to?

    Well, forget all of that…

    Over breakfast with a friend of mine we got onto the subject of old hardware, and he mentioned that he still had the 2012 Mac Pro I used to have at work – and that he wasn’t doing anything with it and I could have it back if I wanted it…

    I said sure – and I’d trade him for the 2013 trashcan, because it’ll run the next-to-latest MacOS natively and will run the latest, Ventura, with a little elbow grease.

    So, after a quick trip down to Castlerock and back I had a new machine to put on the bench…

    Funny thing – that’s my old external Firewire 800 drive that I had on my personal 2012 back in … 2012. I had given it to my roommate when I gave him my 2012, and he had apparently given it to this friend of mine.

    That’s a BTO mid-2012 that came with the single 3.33Ghz 6-core Xeon, 6 gigs of ram, a Radeon HD5770 (in the above photo), and a 1TB HD for the low, low price of about $3500… At work this sat in the server room and was essentially life support for Rumpus (A Mac FTP server) that was used as a secure upload facility for console game builds.

    These days the machine has the same W3680 CPU, but now has 32gigs of ram, a GTX 770 video card, and no HD…

    So I got up on the bench, opened up, evicted the dust-bunnies, and decided to install my 1.2TB Intel 750 PCIE card for primary storage.

    This also meant I needed to install an OS from scratch – and that’s where my entire evening went. See, there are some complications to this machine which make it kind of a deep magic thing to get one running.

    The big complication is that it needs the video card to have custom firmware to be able to display anything before the OS comes up fully, which that Radeon HD5770 has but the GTX 770 does not. So while the GTX 770 is installed, you just kinda stare at a black screen until the login prompt – there’s no Apple logo or progress bars to indicate things are okay.

    To add to this complication, when MacOS went from ‘High Sierra’ to ‘Mojave’, the OS started requiring a ‘Metal‘ capable video card. Metal is an Apple system similar to Microsoft’s DirectX – and the HD5770 does not support this while the GTX 770 does. So to use a relatively recent OS you kinda need to use a video card that doesn’t show you anything until the OS is fully up…

    This becomes frustrating when you’re trying to load an OS from scratch.

    The next complication comes in the form of Apple simply refusing to acknowledge that anything older than OS11 (Big Sur), which came out in 2020, even exists. So to get an installer for MacOS 10.15 and older requires equal parts hackery and hardware…

    For example, you need to go to the “App Store” to download MacOS versions, but if you’re running the current OS (Ventura), when you click “get” the machine pops up the update panel, thinks for a minute, and then tells you that the OS you want to download is older than what you have and doesn’t download.

    And this update error only happens on an Intel-based Mac. If you try it on Apple Silicon hardware, the App Store page for the older OS simply grays out the “get” button and has a banner that tells you the OS won’t run on your hardware.

    So the solution for this was to write a script to downloaded the .PKG files for the installer and then combines them all into the appropriate app container. No biggie – and now I had the old OS I needed – but this was just the beginning.

    The OS installer apps have the facility to create installer media by way of a few terminal commands such as:

    sudo /Applications/Install\ macOS\ Mojave.app/Contents/Resources/createinstallmedia --volume /Volumes/MyVolume

    And this evening I discovered that if you try to do this on an Apple Silicon machine, the OS simply kills the process without any explanation as to why… You just can’t create an old OS installer on Apple Silicon.

    Luckily I have a 13″ Macbook Air with an i3 in it that I use as a television – and it was able to create the USB installer – which is when I had to suss out the next complication…

    I ran into an issue where the Mojave installer would load from USB, but then report that it couldn’t find a Metal-capable card in the system… It turns out that there is a long-standing bug with the older OS installers in that they won’t recognize certain Nvidia cards – but only if you install from USB.

    So I dig out my USB-C to SATA adapter, grab an old 160G SSD, and using the i3 Macbook Air create another installer on the SSD. Then install this SSD on one of the four SATA ports in the Mac Pro and turn it on.

    This time, after a half an hour of waiting and not getting anything on the monitor (remember, I can’t see progress bars or error messages), I decide the Mojave installer isn’t working…

    So – back to the Macbook Air, redo the download script to get ‘High Sierra’, create an SSD installer out of it, stick it in the 2012, and turn it on…

    Presto! I can haz OS!

    And with High Sierra loaded, I was able to do an in-place update to Mojave – which is the last OS before Apple stopped supporting 32-bit applications.

    10.14.6 – as far as I can go and still have Adobe CS6 run…

    And once all of the updates for 10.14 were done, I was able to install and re-key my copy of CS6…

    So – back to where I was a few days ago with the Trashcan, but with a much larger, more power hungry machine… But unlike the Trashcan it’s a machine I actually used to own – like literally. 🙂

    Listening to "Don't Stop Believin'" by Journey

  • Vidya Games

    I’ve kinda orbited around the video games industry since video games were a thing, and accordingly I have quite a few interesting tidbits of hardware laying around – and stories to go with them.

    For example, here is the complete lifecycle of the early XBOX game:

    The clear machine is a DVT-4 development kit, the green one is a debug kit, and the black one is a retail machine. At work we have probably 30 of the green debug kits from back when we did console certification, but there was only one dev kit – and I used it to help clients work out kernel level issues.

    Using that dev kit I’ve written a few things that run on the Xbox, but they are just personal project things for the entertainment value.

    Ages ago I got into programming, computer graphics, music production and sound design, and other such hobbies with the intent of being a one stop shop for game development… It was nice to put all of those skills to use and see the end result run on a console. 🙂

    Here’s another setup from back in the day:

    That’s the old Nintendo development setup. There’s an NDEV and debug (RVT Reader) Wii for Wii games, and an IS Nitro writer and emulator for DS titles. The red PC was the Wii dev box that ran the two RVT burners and the black one was for DS development.

    All in all it was a lot of fun working on early consoles – mostly because anyone could. But as the amount of money in the segment increased so did exclusivity – and eventually you had to be a “name” or owned by Nintendo, Microsoft, or Sony to get the tools to write things. I got out of the business after Playstation 3, because Sony started wanting six digits for dev/debug hardware – if they deigned to even talk to me.

    And Microsoft had gotten just as bad…

    So I kinda moved on to other things, but I keep the hardware around to remember how it used to be. 🙂

    Listening to "Deacon Blues" by Steely Dan