Yes, some Compaq machines were able to support more than 4 partitions.

John Doue wrote:
> Barry Watzman wrote:
>> You are correct in that, at times, on some models (and, at times, on
>> all models in the case of Compaq) they used a non-standard boot scheme
>> with non-standard boot records.
>>
>> Compaq wanted to get around the fact that the "MBR" only allows 4
>> partitions on a drive, period (which has been the case from the
>> original IBM PC-XT in 1982 to this day).
>
> I was not aware they had this in mind. To your knowledge, did they
> manage to get more than 4 partitions on a drive? I do not know what
> IBM's goal was; I'd be curious to know if Lenovo has continued this
> practice.
>>
>> I'm not sure what IBM was doing, but I know that if you took a drive
>> out of some IBM Thinkpads and put it into another machine, or if you
>> took a drive formatted in a non-Thinkpad and put it into some
>> Thinkpads, the drive geometry was not seen the same, and file and
>> drive corruption would occur as a consequence.
>
> I never experienced file corruption, because the drive cannot be
> accessed in the standard way. Just at boot time, you get a geometry
> error message and the machine does not boot. That is very frustrating
> when you have to deal both with TP and "regular" laptop drives.
>