IBM ThinkCentre A50p Information and Software
System Type: 8194 "Stiletto"
Other System Types: 8189, 8190, 8195, 8415, 8432, 8433
A rather capable system released in 2003; with an appropriate name of 'Stiletto,' as it's extremely flexible. It supports up to 3.2 Ghz Northwood CPUs (early Prescotts are supported as well, but inferior to the Northies). The RAM can be expanded up to 4GB of DDR400: which for the time was quite lot allowing them to hold up very well, even with Windows 7/8 if you so desire. However, there's magic to be had as these also run Windows 98: of course you must reduce the RAM to 1GB (or 2GB if you have the Windows 98 RAM mod).
In lieu of the high capacity dual-channel capabilities of these machines, IBM only had [most] major preconfigurations with a single 256MB stick (or even worse, one option came with a single 128MB stick!)-- throwing it back into single channel operation and not taking advantage of its high memory addressability. The best option offered was 8194-LUJ: which got you a 3.2 Ghz Northwood and 1GB of RAM stock OEM. Curiously 8194-Y12 & Y11 were preconfigured with a 'special DOS license', for businesses still relying on DOS. No 8194 machines were released OEM with Windows 98SE.
Downloads
--> A50p User's Guide
--> A50p Hardware Maintenance Manual
--> BIOS 22a (latest version 23-08-05)
--> Windows 98SE 3.3 Unofficial Update Pack
--> SoundMax Audio Driver (OS/2 Warp, Windows 98, 2000, XP)
--> Windows 98 Chipset Driver (only for: 8320, 8419, 8092, 8127, 8183, 8184, 8416, 8417, 8418, 8429)
--> Intel Ethernet Driver (Windows 9x to Windows XP)
Note: all three types of BIOS update methods are included in the ZIP (diskette, ISO, and Phoenix WinPhlash).
Hardware Maintenance
A lot of these A50 systems found themselves used in business environments run 24/7 around the clock. To make matters worse, Rubycon MCZ and Chemicon KZG were popular at this time by OEMs as well. While these series of capacitors were still charged for a premium, their lifespan was far below their specified ratings and they their uF output was incorrect even brand new from the factory. Given these two variables a lot of A50s will have burst capacitors near the voltage regulation or the PCI slots (depending if either of the above flawed series of capacitor was used: sometimes neither KZG or MCZ were used).
If you have an A50 with either of those capacitors, you'll need to take out the system board and recap. Thankfully these are *very* easy boards to work on and they're quite robust. Even better, the power supplies use quality Rubycon/Chemicon PSU series of capacitors which have very stable electrolyte and accurate output voltages. They are a slightly smaller size than most PSUs, however you [can] weasel a standard ATX in the chassis; not really worth it though as the majority of consumer PSUs made use low quality components and have messy output.
Main tools required: Hakko-808, solder (go with 60/40 lead solder), MG Chemicals 'Overcoat Pen' (necessary if you remove a bit of the solder mask), and of course electrolytic capacitors.
Windows 98SE Support
As mentioned in the beginning of the article, the A50p can run Windows 98SE. You need to install the unofficial Windows 98SE update package for the system to recognize the AGP 4x/8x slot properly, along with some other things.
One problem that I have not yet had the time to resolve yet, is the fact that the Windows 98 drivers and all of the updates don't seem to get any audio output working on these computers... even with the IBM Audio PCI adapter (which should be recapped as well). None of the onboard devices work either-- so I would recommend a 3com PCI NIC: a lot of these cards have ended up in recycling depots as well. Running in Windows XP all of the hardware is recognized: so it's most likely a driver bus issue.
(Update 9/27/2014) Further research to see if the A50p (via its ICH5) can be ran properly in Windows 98SE with sound, I read through Intel's '82801EB I/O Controller Hub 5' manual. It does reference Windows 98 as being potentially used, so I cannot see what would stop intel or OEMs for making drivers for it. After installing Intel's package for the drivers, and the unofficial 3.3 Windows 98SE pack, the sound card still shows of having unknown issues. I was not able to get sound working at all through these motherboards, I've ruled it out to a chipset and OS incompatibility. While they make great high-performance Windows 98SE machines, if you need sound they will require a 'ThinkVista' mod. Alternatively, dual-booting with Windows 98 and XP will allow you to have 98 support when needed (without sound), and XP for everything (with sound). Due to the aforementioned chipset incompability, onboard devices won't work but everything else will. XP is 100% functional, as well as Windows 7.
Alternatively if someone had good programming experience with drivers, it wouldn't be impossible to write something to get it going, but that would be a lot of time and effort.
3dfx Capable
Because these computers have the 4x/8x AGP slot, they can safely run a 3dfx Voodoo 4500: allowing VSA-100 to operate on the fastest bus possible, and also giving you loads of RAM and a decent CPU. If you are looking for a system to run an AGP Voodoo 4500, I would definitely recommend this one.
NOTE: It's important that you use the 1.5v 4500 release, and not the 3.3v cards. The only 1.5v 4500 card released is the commercial north american card, the PCB is a complete square and it usually has the AAVID fans:
The 1.5v cards usually are in an L-shape, or the uncommon chinese release cards (which aren't in an L-shape, but look different from the 1.5v north american card):
ThinkVista mod
The ThinkVista mod is essentially sticking in a more Windows 98SE compatible NetVista board in the A50 / S50 ThinkCentre tower chassis. There are two major boards I can recommend for this conversion:
#1 NetVista 6790 Motherboard (FRU 73P0544)
It appears the NetVista 6790 motherboard which is very similar to the A50p, but with some slightly older chips such as ICH2. It also appears IBM preconfigured some with Windows 98SE out of the factory: 6790-26U and 6790-36U. I am PRETTY sure these can run windows 98SE just fine with the audio, but since the one I ordered was a lemon, I cannot confirm.
#2 NetVista 6578 Motherboard (FRU 09K9982)
This is a slightly older Pentium 3 socket board. However, it also feaures a PCI-X and AGP universal slot; which allows a 3dfx Voodoo 5500 AGP 2x card to work without issue.
Note: The NetVista boards are sometimes configured with high quality Rubycon capacitors, or low quality Taiwanese ones. I've seen some with FPcaps as well. Therefore I caution anyone who wants to get the NetVista boards to make sure you take a look what the board has. If you don't have the resources to recap them, they won't be a good alternative. However, most IBM computers of this vintage need new capacitors at this point anyways. I believe IBM was aware that many of the NetVista boards were plagued with low-quality capacitors from their contractors as ones with high quality caps will have orange 'SERVICEABLE USED PART' stickers.
So far these have been my board of choice for the ThinkVista mods as they have the universal AGP and a more 'era compatible' Pentium 3.