PENTIUM II technical info needed - your historical tech help

[andre1000]

My motherboard is an old one. I use it for recording / archiving
radio shows. It's a Premio 212B = OEM version of MSI's MS-6112

This is a generic question about Pentium II CPU that fits
the motherboard.

I have a Pentium 266 slot 1 cpu and heatsink now
in my computer. I have an opportunity to buy a Pentium
II 350mhz /100mhz bus CPU for $5 guaranteed to work.

My question is this:

Since I can set the jumpers on the motherboard for 333mhz / 66mhz bus
is there any reason that the Pentium 350 / 100mhz bus chip can't be
used and simply run at a reduced speed?

Thank you very kindly.

sincere regards,

andre

PS. I also wondered two other things.
Is a Celeron with 128Kb of L2 as fast or faster than a Pentium II's
512Kb because I read somewhere that the Celeron's L2 cache runs at
CPU
speed where as the Pentium's L2 runs at 1/2 CPU speed.

And will the heatsink for a Celeron 266 fit a Pentium II 266?

 

[cquirke (MVP Win9x)]

On 18 Dec 2004 08:08:42 -0500,

My motherboard is an old one. I use it for recording / archiving
radio shows. It's a Premio 212B = OEM version of MSI's MS-6112

This is a generic question about Pentium II CPU that fits
the motherboard.

I have a Pentium 266 slot 1 cpu and heatsink now
in my computer. I have an opportunity to buy a Pentium
II 350mhz /100mhz bus CPU for $5 guaranteed to work.

A Google suggests the mobo doesn't support 100MHz base speed, i.e. is
based on a pre-Deschutes chipset. Which means the voltage may fry the
Deschutes, which has smaller fabrication and ?lower voltage.

Since I can set the jumpers on the motherboard for 333mhz / 66mhz bus
is there any reason that the Pentium 350 / 100mhz bus chip can't be
used and simply run at a reduced speed?

Supply voltage.

---------- ----- ---- --- -- - - - -

On the 'net, *everyone* can hear you scream

 

[Torbjorn Lindgren]

My motherboard is an old one. I use it for recording / archiving
radio shows. It's a Premio 212B = OEM version of MSI's MS-6112 [...]
I have a Pentium 266 slot 1 cpu and heatsink now
in my computer. I have an opportunity to buy a Pentium
II 350mhz /100mhz bus CPU for $5 guaranteed to work. [...]
Since I can set the jumpers on the motherboard for 333mhz / 66mhz bus
is there any reason that the Pentium 350 / 100mhz bus chip can't be
used and simply run at a reduced speed?

It may not support the voltages required for the "newer" CPU, so it
could fry the CPU.

Also, the PII in question is most likely "multiplier locked", which
means that it won't do 333/66. It'll take the bus-speed and run at
3.5x that (3.5x100=>350).

With this motherboard that means 233 MHz (263 when overclocking
everything to 75 Mhz)... This is slower than your existing CPU at 266
MHz (300 MHz at full overclocking, 75MHz bus speed).


It might be possible to go higher than 333/66, but you would need to
have the following items:
* Slot 1 converter board, with power conversion capability and
supporting 66 MHz bus speed
* A suitable CPU, basically a 66 MHz Celeron...
* A bit of luck, because the BIOS may not like the new CPU... They
should have lists of motherboards where it's known to work.

PowerLeap has converts that MAY work, the "PL-iP3/T 733 MHz Intel
Celeron", but note that MS-6112 isn't in the lists, there's a fair
chance that it won't work...

And the adapter & CPU isn't exactly cheap at $100 (plus freight),
you're probably much better of with either a new machine or an used
motherboard/CPU compatible with your memory and power supply, so not
too new, and presumably 66 Mhz unless you replace the memory.

Essentially an older 66 MHz bus speed Celeron (128 KB cache, PII/PIII
based).

Pricewatch has motherboard/CPU's in the $80-$100 range, but I think
all of the will require both new memory (you have PC66, most are DDR
and even the cheapest has PC133..) and PSU, pushing it up a bit
further.

PS. I also wondered two other things.
Is a Celeron with 128Kb of L2 as fast or faster than a Pentium II's
512Kb because I read somewhere that the Celeron's L2 cache runs at
CPU speed where as the Pentium's L2 runs at 1/2 CPU speed.

It depends on what you run... The size of the working set is critical
here. At the same bus speed the Celeron will win some smallish
programs (including some benchmarks), but probably loose in many real
programs...

However, above 333 MHz (+ the 300/100) the PII/PIII will also have
more memory bandwidth (100 or 133 MHz instead of 66 MHz), which helps
a lot. There the PII/PIII will be significantly faster than the
equivalent clocked Celeron in almost everything, but even there
there's some few exceptions, and many (artificial) benchmarks will
show it to be much closer than it is in real programs.

And will the heatsink for a Celeron 266 fit a Pentium II 266?

No idea.

 

[Tony Hill]

On 18 Dec 2004 08:08:42 -0500,

My motherboard is an old one. I use it for recording / archiving
radio shows. It's a Premio 212B = OEM version of MSI's MS-6112

This is a generic question about Pentium II CPU that fits
the motherboard.

I have a Pentium 266 slot 1 cpu and heatsink now
in my computer. I have an opportunity to buy a Pentium
II 350mhz /100mhz bus CPU for $5 guaranteed to work.

My question is this:

Since I can set the jumpers on the motherboard for 333mhz / 66mhz bus
is there any reason that the Pentium 350 / 100mhz bus chip can't be
used and simply run at a reduced speed?

Yes.

First off, the "reduced speed" that the chip would run at is NOT
333MHz/66MHz bus, but rather 233MH/66MHz bus, ie slower than you're
current processor. The reason for this is that the multiplier is
likely to be locked at 3.5x, so no matter what bus speed or multiplier
you set on your motherboard, it will run with a 3.5x multiplier.
Combine that with a 66MHz bus speed and you get a 233MHz chip.

Beyond that you also can have some very definite possibilities of
incompatible chips due to voltage differences. In fact, it's quite
possible to harm either the processor or the motherboard by running a
chip with a voltage that is not supported.

PS. I also wondered two other things.
Is a Celeron with 128Kb of L2 as fast or faster than a Pentium II's
512Kb because I read somewhere that the Celeron's L2 cache runs at
CPU
speed where as the Pentium's L2 runs at 1/2 CPU speed.

As is often the case, it depends. On average the two chips were
fairly close, though I would give the edge to the PII, especially as
clock speeds climbed. Where the 300A MHz Celeron and the 300MHz PII
were pretty comparable in performance, the 400MHz PII would have been
faster than a 400MHz Celeron. The slower bus speed and greater
dependence on main memory were a bit of a double-whammy that hurt the
Celeron's performance later on in life.

Still, these Celeron chips were fairly respectable performers, MUCH
more so than the first of the P4-generation Celerons (ie the Celeron
2.8GHz that gets smacked silly by a 2.0GHz P4). Of course, the same
was definitely NOT true for the very first Celeron chips that did not
have any L2 cache at all, but fortunately those chips were fairly
rare.

And will the heatsink for a Celeron 266 fit a Pentium II 266?

My memory is a touch fuzzy to say for certain, but I'm believe the
answer is no. The Slot 1 Celeron chips were a bare board and had a
different retention mechanism than the cartridge-style Slot 1 PII
chips. I'm almost certain that this difference also meant different
heatsinks.

 

[Franc Zabkar]

My motherboard is an old one. I use it for recording / archiving
radio shows. It's a Premio 212B = OEM version of MSI's MS-6112

This is a generic question about Pentium II CPU that fits
the motherboard.

I have a Pentium 266 slot 1 cpu and heatsink now
in my computer. I have an opportunity to buy a Pentium
II 350mhz /100mhz bus CPU for $5 guaranteed to work.

My question is this:

Since I can set the jumpers on the motherboard for 333mhz / 66mhz bus
is there any reason that the Pentium 350 / 100mhz bus chip can't be
used and simply run at a reduced speed?

I haven't had much, if anything, to do with Pentium IIs, but it seems
to me that concern over the power requirements may be unwarranted. If
the original motherboard can accept a 333MHz CPU at a certain Vcore
setting, then surely a later 350MHz CPU with a lower Vcore isn't going
to challenge it?

My reading of the motherboard manual suggests that there are no Vcore
voltage jumpers. Instead the Vcore voltage appears to be automatically
set by the CPU's own VID pins. Hence there is no possibility that the
wrong voltage may be selected, only that the existing Vcore regulator
may not be able to supply a higher current, if required.

In any case the following URL suggests that the 350MHz and 333MHz CPUs
are both 2.0V processors with identical power requirements:

http://support.intel.com/support/processors/pentiumii/sb/CS-011169.htm#Voltage
Requirements


- Franc Zabkar

 

[keith]

I haven't had much, if anything, to do with Pentium IIs, but it seems
to me that concern over the power requirements may be unwarranted. If
the original motherboard can accept a 333MHz CPU at a certain Vcore
setting, then surely a later 350MHz CPU with a lower Vcore isn't going
to challenge it?

Not necessarily. IIRC earlier PIIs used a 4-bit buck converter DAC
that only went down to 2.1V. Later PIIs added a bit to the DAC so the
voltage could go down to 1.3V.

My reading of the motherboard manual suggests that there are no Vcore
voltage jumpers. Instead the Vcore voltage appears to be automatically
set by the CPU's own VID pins. Hence there is no possibility that the
wrong voltage may be selected, only that the existing Vcore regulator
may not be able to supply a higher current, if required.

IFF the board interprets the fifth bit, you're correct. If, on the
other hand, the processor requested 2.00V (VID=00001) a board
with only a four bit DAC would interpret this as 0001 and supply 3.4V to
the processor. ...not good.

In any case the following URL suggests that the 350MHz and 333MHz CPUs
are both 2.0V processors with identical power requirements:

http://support.intel.com/support/processors/pentiumii/sb/CS-011169.htm#Voltage
Requirements

I couldn't remember when the fifth bit was added. It seems from the
above that it was added at least by the time the 266MHz processors came
out.

 

[Franc Zabkar]

Not necessarily. IIRC earlier PIIs used a 4-bit buck converter DAC
that only went down to 2.1V. Later PIIs added a bit to the DAC so the
voltage could go down to 1.3V.


IFF the board interprets the fifth bit, you're correct. If, on the
other hand, the processor requested 2.00V (VID=00001) a board
with only a four bit DAC would interpret this as 0001 and supply 3.4V to
the processor. ...not good.


I couldn't remember when the fifth bit was added. It seems from the
above that it was added at least by the time the 266MHz processors came
out.

The motherboard manual states that its Vcore regulator conforms to
Intel's "VRM 8.1 DC-DC Converter Specification". Intel's documentation
(http://www.intel.com/design/chipsets/designex/29765101.pdf) confirms
that V8.1 adds support for VID4, the fifth bit.


- Franc Zabkar