Extended partitions on Microbee 512k bios and cf

Rod April 16, 2026

Extended partitions for cf/512k bios on the Microbee

How to create extra partitions and access them. There is lots of unused space on the cf images that could be used as archive or whatever but people may not know how to access or use it.

There are some constraints but it is still useful storage and it's free!

extended partitions of mbee 512k bios

Boot

check for number of mounted hd/cf partitions (flash screen shows this, or 'hd list cf0:')

We will replace the last primary partition with an extended partition and then we can add aa replacement partition for the deleted one and other new partitions)

unmount last partitions

ie if 4 partitions A->D then

hd umount d:

then we need to add new partitions

part

d

4

n

4

e

accept defaults

doing a print (p) at this stage should show 3 primary CTOS partitions and one DOS 3.1+ extended partition

Now add extra extended partitions as required. Remembering that the first sector is reserved as a partition table

so accept default start and make the end value the same increment as existing partitions.

'q' exits without saving any changes.

'w' exists writing all changes

'm' help!

Example from 1 1GB CF:

Info from 'part'

[ptbl] 0 size 1 0/0/1 - 0/0/1

[free] 1 size 62 0/0/2 - 0/0/63

* 1 CTOS 63 size 9009 0/1/1 - 8/15/63

2 CTOS 9072 size 9072 9/0/1 -17/15/63

3 CTOS 18144 size 9072 18/0/1 - 26/15/63

4 CTOS 27216 size 9072 27/0/1 - 35/15/63

[free] 36288 size 1993824 36/0/1 - 2013/15/63

Now to add extended partitions we need to delete the last Primary partition (4)

So, delete partition #4

d

4

then replace it with an extended partition using up the rest of the drive

We accept the defaults for start and end values.

n

e

cr

If we 'p' the partition table at this point we see the change to partition 4 it's now:

4 DOS 3.3+ Extended 27216 size 2002896 27/0/1 - 2013/15/63

[ptbl] 27216 size 1 27/0/1 - 27/0/1

[free] 27217 size 2002895 27/0/2 - 2013/15/63

If we now add a new partition it will automatically be an extended partition, we just

need to accept the start and set the end. To make it near enough to the same size as existing

partitions if you look at the existing partition end c/h/s they increment the 'c' value by 9

with the same h/s values, so our new end value is 26/15/63 + '9'/0/0 == 35/15/63, and the

next partition would end at 35/15/63 + '9'/0/0 == 44/15/63 and so on.

So:

n

cr

35/15

And now if you 'p' the partition table it has this at the end:

5 CTOS 27279 size 9009 27/1/1 - 35/15/63

[free] 36288 size 1993824 36/0/1 - 2013/15/63

Each extended partition creates a new partition table similar to the first primary partition.

After saving this back to the disk by using the 'w' command it will tell you to reboot.

At this point the new partition will mount as as the d: drive however it hasn't been formatted yet.

We use 'eraram' program to format fixed disks.

so if our new partition is d:

we run

eraram d:

All done!

If you have more partitions than available space for the ALV's, when you boot the system should detect

your partitions but won't mount then as it has run out of space. Note it always mounts the first cpm partitions

it finds. (partition 4 won't mount as it is a different type in our example, it's replaced by partition 5).

If you want to access the other partitions then you need to unmount a partition then mount the required one.

So using the 'hd' program (for example) to mount a new partition (6 as an example) in the place of the D: drive,

(see function keys note)

hd umount d:

hd mount cf0:6

You can now access partition 6 as the d: drive.*

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