Re: MicroVAX 3100/20 is apocalyptically slow even with 32MB of RAM

> On Apr 17, 2026, at 4:03 PM, John Klos <[email protected]> wrote:
>=20
>> I have a MicroVAX 3100/20 with 32MB of RAM that once ran NetBSD many =
years ago. I recently had occasion to replace its disk and install 10.1, =
and it is superlatively slower than I remember it being. It?s so slow =
that it?s been trying to just bootstrap pkgsrc for about a week now, =
with pauses to allow the daily cron script to complete otherwise it =
won?t complete in less than 24 hours. The system time loses about 10-15 =
minutes a day, presumably because it can?t keep up with the clock =
interrupts. This is after I copied the GENERIC kernel config, stripped =
out all of the VAX models and devices that weren?t needed, and stripped =
out all of the RAM-based filesystems.
>=20
> I have a VAXstation 4000/30 that has a defective CPU cache. Because of =
this, it benchmarks quite similarly to a 5 MHz 11/780, even though it =
runs at 25 MHz. I wonder if your cache isn't getting turned on =
correctly, or if your cache is failing...

I=E2=80=99ll have to look at the test results next time it powers up. I =
don=E2=80=99t think it flagged any hardware faults, and I=E2=80=99ve =
even replaced the nvram battery with a modern substitute.

>> I don?t think RAM is the issue because I haven?t seen it go above =
12-14MB active in top. It uses more swap than it does RAM.
>>=20
>> Is there something configuration-wise I should try, or is this model =
just too slow to be supported anymore?
>=20
> Your machine should be at least half as fast as my fully working =
VAXstation VLC. I'm running NetBSD 11, and it really isn't any slower =
than NetBSD 9 or 10. Do you know what version of NetBSD you had on it =
many years ago?

I want to say NetBSD 4 or 5? Maybe earlier? It was around the time that =
SCSI DMA was fixed on the 3100s and we didn=E2=80=99t have to use PIO =
mode anymore.