In the summer of 2021, Youtuber Adrian Black was restoring an IBM 5170. And he lamented that he wasn’t able to get all of the original parts working together and have a machine that would do what he wanted. It wasn’t a pure IBM 5170 anymore. One of the things he did was put a Phoenix BIOS in it, which received mixed reactions. But that brought to mind another option someone who needed to soup up a 5170 in the late 80s could have used: MR BIOS. What was MR BIOS?
MR BIOS: The power user’s BIOS
MR BIOS was one of those products you found in ads in the back pages of magazines like PC Magazine. If you were trying to upgrade your PC and ran into compatibility issues with newer hardware, you called them up, told them what kind of system you had, and they would sell you replacement BIOS chips that you swapped in for your original BIOS. When flash memory became common, they could just sell you a file that you flashed onto your BIOS in place of the free BIOS upgrade you could get from your manufacturer. Which was always less capable.
A MR BIOS would overcome hard drive size limitations, weird compatibility issues, and allow you to adjust cache and memory timing settings. Tom’s Hardware didn’t talk about it as far as I recall, but early long-gone tech sites that competed with it sometimes did. You paid money for it, but if you wanted the fastest machine possible, a MR BIOS could put you over the edge. Some obscure setting might let you adjust things that let you overclock more successfully. Or if you were lucky, you might be able to tune some settings to get just a touch more speed out of a successful overclock.
It also added capabilities that were sometimes rare in other BIOSes, such as support for four floppy drives, support for 2.88MB floppies, and custom IDE drive types.
Who bought them?
A MR BIOS wasn’t something that everyone had, by any stretch. But your local PC guru, whoever that happened to be, undoubtedly had used one to fix some obscure issue, and might have had one themselves.
If you want a retro PC that would have been the ultimate dream machine of its time, or is just a bit more practical, a MR BIOS is a worthy upgrade for it.
In my experience at least, more people talked about them than bought one. It was always something people wanted, but there was always one other thing that cost $100 that they wanted more. But the product served a purpose and clearly some people did buy them.
History of MR BIOS
The “MR” in MR BIOS stood for Microid Research. Information on them is surprisingly hard to find. In their 1993 book on 486s, Joseph Haas and Thomas Jungbluth referred to MR BIOS as “relatively new.” The copyright dates on surviving images suggest the company was founded no later than 1989. In 1993, that would have still counted as relatively new.
While some motherboards did ship with a MR BIOS from the factory, it was more common as an aftermarket upgrade. When an older PC wouldn’t work with a newer IDE drive, or an upgrade CPU wouldn’t work right, the easiest way to fix it was to get a replacement BIOS from MR BIOS. Yes, in some instances a motherboard swap was more practical, but often a new motherboard didn’t work with your existing memory. While the $99 price tag was steep, a MR BIOS didn’t have a slippery slope of additional hidden costs associated with it.
While obscure today, the company appears to have been reasonably successful. They produced BIOS upgrades for about 500 known motherboards, and images of about 75% of them are known to still exist.
Unicore, Microid’s main rival, bought Microid Research in late 2001, in the late September to late November timeframe. Unicore phased out the Microid’s product line soon after.
Capabilities of MR BIOS
The final MR BIOS version was version 3.46. Some people on old forums have reported using hard drives up to 30 GB with the final version. If you want to use a 32 GB SD or CF card on your Pentium-class retro PC, you may be able to do it, if you can track down a MR BIOS version 3.46 for your motherboard.
The other upside comes in 386 and 486 PCs. If you have a later 486 CPU, a MR BIOS will enable writeback cache in it for improved performance. And if you have one of the weird 386/486 hybrids like those from Cyrix in a 386 board, a MR BIOS will enable the caches in those for better performance.
For a 286-class system, it can resolve compatibility issues with flash memory devices that work in 486 and Pentium-class machines but just don’t want to work in a 286. It won’t resolve all of them, but will make your 286 less picky about what it wants to work with.
If you want a MR BIOS today, it’s tricky. First you have to find the appropriate one for your board. If you do that, you may be able to flash one onto the motherboard using the manufacturer’s flash upgrade utility if the board is new enough to use flash. If not, you’ll need to burn an EPROM. A TL866 is a popular and capable modern EPROM programmer that works on new PCs and costs around $50.