How did Microsoft store 1.68 MB on Windows 95 Setup diskettes?

foreign [Music] 95 the operating system that introduced the start button enabled its users to easily access the internet and arguably was the operating system with a personality be it start me up the iconic Rolling Stones song used in Microsoft's massive advertisement campaign or popular actors Matthew Perry and Jennifer Aniston from the sitcom Friends looking for Bill Gates about a role in a video guide to Windows 95. this is Jennifer Aniston I'm Matthew Perry we're here to see Mr Bill Gates about a possible starring role in the video guide to Microsoft Windows 95. whatever it was Windows 95 was a big hit and sold over 40 million copies in its first year of availability making it until that time the largest selling version of Windows ever Windows 95 was mainly distributed on CD-ROM you may have seen my video where I installed Windows 95 on a 386 with 40 megahertz and 32 megabytes of memory in that video I actually installed an oem version of Windows 95 from CD I am not sure how many 386 systems were upgraded with a CD-ROM drive back in the day but most likely the number was very small so what if you want to keep your old 386 retro PC as authentic as possible without an optical drive attached if all you have available is a floppy drive then you're in luck Microsoft released Windows 95 on 13 floppy disks for users not owning an optical drive later versions of Windows 95 required more than 20 floppy disks of course you could copy the installation files to your hard disk and start the installation from there and that is probably the preferred way if you just want to get windows installed but for the purpose of this video we will focus on the floppy disk edition of windows 95. these days it is quite difficult to get your hands on a set of original Microsoft Windows 95 floppy disks in working condition but you can find disk images online ready for you to copy to physical floppy disks the floppy disk bundle usually comes with a boot disk to start your PC and then you get the Windows installation disks but there is something odd here you may have already noticed that the boot disk as well as the first installation disk images are smaller in size compared to the rest disc 1 requires one million 474 560 bytes of space this is the regular size of a standard floppy disk IBM or dos formatted the rest of the images take up more space 1720 320 bytes to be precise what is going on here did Microsoft use special non-standard floppy disks the short answer is no Microsoft used standard three and a half inch floppy disks if you're interested in the long answer then I recommend watching this video to the end we all have seen floppy disks being advertised having 1.44 megabytes of available space using this marketing formula Microsoft managed to increase the size of their Windows 95 installation disks to 1.68 megabytes we are talking about an additional 245 760 bytes that are written to a standard floppy disk reducing the total required floppy disks for Windows 95 from 15 to 13 disks this was not only a good way to cut cost it also prevents a simple disk copy as we will see later so how did Microsoft Store more data on standard floppy disks to answer that question we should have a quick look at the structure of a floppy disk a flexible magnetic disc is enclosed in a plastic housing covered in fabric to remove dust particles in its basic unformatted form a floppy disk can actually store around 2 megabytes of data when a floppy disk is formatted using a tool like the MS-DOS program format information about its layout is stored on the floppy disk and thereby reducing its total usable space this includes physical characteristics like number of tracks sectors and gaps between sectors but also logical information for the file allocation table boot sector root directory and clusters when a high density double-sided floppy disk is formatted it ends up with 80 tracks and 18 sectors per track each sector holds 512 bytes of data with this information we can actually calculate the size of a formatted IBM compatible floppy disk 80 tracks times 18 sectors times 512 bytes times two sides this is a total of 1474 560 bytes the tool I'm using in this video is FD format from Christoph Hostetter it provides a lot more information than the regular format tool included in DOS and as we will see has a lot more features here we can see that on top of the Lost space due to the physical alignment of tracks and sectors 33 sectors are used to store file system information 512 bytes are dedicated to the boot sector which is a single sector on the disk 7168 bytes are used for the root directory another 14 sectors and finally 9216 bytes or 18 sectors are used for the file allocation table from the total 2880 sectors only 2847 sectors are available to the user or 1457 664 bytes of usable space an image file of a diskette has the information of boot sector root directory and file allocation table included therefore it has the full size of a 2880 sector disk or 1474 560 bytes as we have seen before the first diskette of the Windows 95 installation set has a size of a 2880 sector disk therefore there is no issue writing this image to a regular IBM compatible floppy disk the tool to write images is part of the FD format collection a link to an archive with all the applications I'm using is in the video description the Right image tool provides a few additional details after a bit about the author you can see information extracted from the floppy disk we have 80 tracks 18 sectors per track and two sides identical information is displayed below but this time it refers to the floppy image the tool finalizes its work without any success message you're just back at the MS-DOS input prompt now let's try to write this cat number two of the Windows 95 installation set the tool quits immediately with an error message source file and destination disk have different formats nothing has changed from the information extracted from the floppy disk this is no surprise as I'm using the same disk I used to write disk at number one so let's examine the information of the image file we still have 80 tracks and two sides but this image file has 21 sectors per track that is three sectors or 1536 bytes additional space per track to calculate the total extra space we get using such a format we multiply three sectors times 80 tracks times 512 bytes times two sides and this will give us 245 760 bytes we have seen this number before this is the extra space and image file from the Windows 95 installation set requires and this is how Microsoft stored more data on a standard floppy disk by increasing the sector count per track from 80 18-21 but how is this possible let's have a look at the format tool that comes with MS-DOS the help screen does actually have the commands listed that should allow us to specify tracks per site and sectors per track well that is super convenient let's try it out format a T 80 480 tracks and n21 421 sectors per track and no format tells us that our floppy Drive does not support the given parameters what a lie see when Microsoft released Windows 95 on those floppy disks with more space it not only saved them to disks it also made it a lot more difficult to copy them acting like a copy protection it wouldn't be wise for Microsoft to ship the tools that can be used to bypass their sudo copy protection they wear tools however that could format floppy disks with 21 sectors per track this format is also known as DMF or distribution media format Microsoft used this format for many other distributions like Word and Excel for Windows 95 and there is even a Windows 98 first edition floppy version one more thing to note is that DMF floppies could also be created using Macs so it isn't a Microsoft thing now I'm switching to the tool FD format same as the MS-DOS tool format it allows to specify how many tracks and sectors the floppy disk should have it also offers many additional options which I will get to in a moment but first let's try to format a disk with 80 tracks and 21 sectors per track the syntax of this command is FD format drive a t8480 tracks and n21 for 21 sectors per track when you open the help file provided with FD format you will also find a list of Handy shortcuts that make it easier to create floppy disks in DMF format instead of specifying the tracks and sectors you can simply specify F 168 as a parameter this is the same as formatting the disk with 80 tracks and 21 sectors per track while the tool is formatting we get more information about the floppy most of which can be controlled with extra parameters we have a double-sided floppy disk which is implied here by mentioning two heads 80 tracks per side and 21 sectors per track I don't know much about interleave and what this exactly does but I noticed that an interleave of 1 is twice as fast as the current setting of two more about this later Gap length specifies the area left blank between sectors furthermore we can see that we can have 224 entries in the root directory this means that you can have 224 files or folders on drive a in the root directory we can also see that a cluster contains one sector of 512 bytes the standard size of a sector on a floppy disk I will not get into sector shift in this video because I was not able to notice an increase in performance which this feature should make possible here is the explanation from the readme file that chipped with FD format you can pause the video and read it if you're interested my assumption is that at some point formatting utilities employed sector shift is a standard method when formatting floppy disks once the format is complete we get a summary instead of 2880 sectors we now have 3360 sectors on the same floppy disk 480 sectors more all because we got three extra sectors per track when we went from the standard 18 to 21 sectors if I understand correctly then clusters contain the sectors that can be used by the user we have 35 less clusters available than number of sectors remember that in our case a cluster contains only one sector therefore we get 3325 clusters available to the user in the summary below we see the total bytes of the floppy disk one million seven hundred twenty thousand three hundred twenty we have seen this number before it is the size of our installation diskette number two of windows 95. the boot sector occupies only one sector then we have 14 sectors for the root directory and 20 sectors are used for the file allocation table two sectors more compared to a regular floppy disk those two extra sectors are probably required to manage the extra space that is now available on the disk the usable space of this floppy disk is one million seven hundred and two thousand four hundred bytes let's try to write this kit number two of Windows 95 to the floppy disk with 21 sectors per track as you can see the image writer no longer complains about the source image and the destination disk having different formats let's write another image to the floppy let's write this kit number three as well just to be sure that we have found the format Microsoft was using to ship Windows 95 on floppy disks the image also seems to be written without complaints let's have a look at the files that were written to the floppy disk OK there is only one file and it uses up the entire space of the disk wait a second have a look at the space of this disk when we formatted the disk with 80 tracks and 21 sectors per track the maximum usable capacity was one million seven hundred and two thousand four hundred bytes it looks like we have not yet discovered the correct setting how Microsoft formatted the disks so far we have only changed the physical characteristics of the floppy disk by increasing the sector count per track from 18 to 21. there are however a few ways to optimize The Logical parameters of the diskette if you know for instance that you will only store large files or a limited number of files on the floppy disk you can optimize it accordingly let's start by changing the cluster size to two sectors per cluster this is only advised if you store larger files on the disk as any unused space of a cluster is wasted for instance if you store a file of size 412 bytes on a disk with a cluster size of two sectors 612 bytes are wasted and cannot be used for other files in case a cluster is made of one sector you would waste 100 bytes only so it really depends on your use case with a cluster size of 2 the number of sectors required for the file allocation table drops from 20 sectors to only 10 sectors unfortunately we lose one sector to the root directory which increases from 14 to 15 sectors that may be due to the requirement to have an even number of sectors to satisfy two sectors per cluster this leaves us with nine additional sectors which will be available to the user for a total of 3334 sectors since a cluster is made of two sectors the total number of clusters is 1667. now the floppy disk has a capacity of 1707 thousand and eight bytes available for data we are still missing 18 sectors or 9216 bytes we can optimize a little further if we restrict the number of files and folders that can be written to the root directory of the disk with a parameter D16 we tell the tool to format the disk allowing a maximum of 16 entries in the root directory that literally does what it says you won't be able to have more than 16 files or folders in the root directory now only one sector is used for the root directory down from 15 sectors before we freed another 14 sectors which are added to the total capacity of the floppy disk now that this has a capacity of 1714 176 bytes available for data we are really close to the format Microsoft used four sectors are still missing we just need to find another 2048 bytes but before we go look for the missing bytes let me show you what happens when you want to add more than 16 entries into the root directory I already created 16 entries and this is the 17th folder I try to create yeah the file system run out of space OK back to the missing four sectors the boot sector and the root directory are already at one there is nothing else we can do here but maybe we can reduce the file allocation table size we have already seen a drop to half the amount when we went from one to two sectors per cluster we make it to Microsoft's format if we increase the sectors per cluster to four let's try that now and see what we get on the summary screen one million seven hundred sixteen thousand two hundred twenty four bytes available looks like we finally found the parameters Microsoft used to create their floppy disks for Windows 95 and indeed the sectors used for the file allocation table have reduced by four sectors to six in total and the freed sectors are available to the user for storing data increasing the cluster size does not free up a lot of space therefore I would stay at a maximum of two sectors per cluster FD format even warns us that dos only supports a cluster size of one or two I couldn't verify this but it may be that older versions of Dos are not able to read floppy disks with a cluster having more than two sectors but we are not done yet we can squeeze a few more bytes from the floppy disk by over formatting it to 82 tracks unlike increasing the number of sectors from 18 to 21 per track adding two additional tracks per side is not recommended and should not be used if you store important data on floppy disks but who does this these days anyways well Boeing does it uses floppy disks to update software on their 747 airplanes the two additional tracks are placed on an area that usually is not supposed to hold data and there is no guarantee that it will work I don't know where those extra tracks are located but we are drifting further away from the standard which may make this floppy disk less compatible with hardware and software any information that is stored on those extra tracks may not be recoverable and in the worst case can render the floppy disk unusable under dos or Windows it probably is a good idea to let scan this test the surface of the floppy disk a surface test can determine a floppy disk's fault free operation but it is still no guarantee that this disk will work for an extended time and there may be more issues waiting not all floppy drives support 82 tracks the only way to know for sure is to try your luck with your own floppy drive I have two floppy drives which I tested one is from mitsumi and the other one is from tiak both drives had no issues formatting a floppy disk with 82 tracks per side the mitsumi drive has a large x-posed rotating disc which makes it difficult to place on a Surface the tierg on the other hand has its moving Parts completely concealed within the housing with 82 tracks per side we added a total of four tracks with 21 sectors each that means that we should get an additional 84 sectors or 43 000 and 8 bytes extra space the boot sector and the root directory remain at one sector each but the file allocation table increased now from 5120 bytes or 10 sectors to 6144 bytes or 12 sectors this floppy disk has a usable capacity of 1756 160 bytes by the way 82 tracks and 21 sectors was the absolute maximum I could set any larger number would cause the disk to fail here is a summary of all configurations that we have seen in this video so far with changing the format we can get 298 496 bytes of additional space on a regular floppy disk that is about 20 extra space the final topic I want to discuss is interleave in this video you may have seen a value of one or two for this property all I can say is that the larger the number the slower the transfer speed of the floppy disk with an interleaf of 1 the disk transfer score is around 60 or high-end this Benchmark with an interleave of 2 we drop to around 30 or half the speed interleaf is selected automatically by the formatting tool and I believe it is a physical constraint depending on other parameters like sectors per track and GAP length you cannot force a DMF installation disk of Windows 95 to use an interleave value of 1. the disk simply is not accessible when the setting is used that would also imply that the Windows 95 setup is slower using the DMF format compared to using a regular floppy disk formatted to be IBM or dos compatible with around 1.4 megabytes yes you would need two more disks but based on the Benchmark results they would transfer data twice as fast and probably speed up a Windows 95 installation you can even hear the difference in Access speed between interleaf 1 and 2 when used on the same floppy disk the largest size I could manage to create while keeping the disc at its Peak Performance was to use the following parameters 82 tracks 20 sectors per track 16 route entries and two sectors per cluster with this configuration we have 3268 sectors and 1634 clusters available the total size of the floppy is 1673 216 bytes or using the marketing formula to determine its size 1.64 megabytes I am curious how it would be to install Windows 95 from 13 floppy disks just as a comparison in size the 13 floppy disks have a total size of 21 megabytes the Windows 95 CD image has almost 360 megabytes that is 17 times the size of the floppy images I wonder how much was cut in the floppy version if you know let me know in the comments and if you want me to make a video about it let me know too and we have reached the end of this very long video I hope you enjoyed the content even though there was quite a bit of math here in there don't forget to subscribe to my channel if you haven't already done so and press the Bell icon so you won't miss any of my upcoming videos in the future thanks for watching and I will see you in one of my other videos

Channel: Bits und Bolts

Views: 197,877

Keywords: Windows 95, DMF, 1.68MB, 1.68, Floppy, FDFormat, format, Diskette, Sector, Cluster, 1.44, 1.72

Id: qSehRwClXNk

Length: 22min 11sec (1331 seconds)

Published: Thu Jun 15 2023