Compatable Processor

Hello PB group,

I have an old 486 - PB Axcel 251 from 1995. I have made the full upgrades
for the modem,56K, and all the memory (64 ram, 512 L2cache,and 2 mb for
video ram) but can't for the processor. Its a DX-2 /66mhz chip, socket 3
type. I got the upgrade that the manual recommended, Pentium Overdrive 83
5V. and it was not compatible. When I looked it up on the internet, I found
out I needed an interposer. Packard Bell said nothing about this in the
manual. I look at AMD processors and they had the same problem.
I tried a DX 4 - 100 and changed the bus setting ,but that
didn't work either. I saw an old posting that said to use the DX4 - 100ODP
and I wouldn't have to bother with an interposer. I didn't realize there
were two types of DX-4 100, and I got the wrong one. I have looked on Ebay
and other places and can't find the right one - the ODP one. I'm thinking
they are all gone. Any ideas on this?
I got this computer brand new in 1995 and since it was such
a useful tool at the time I decided to keep it as a working antique.

This computer originally came with Windows for Workgroups, 3.11. It was
upgraded to Windows 98 Second Edition so it is still able to connect to the
internet, but the speed is quite slow....and yes it has a firewall.

Hi 60 !

( inserting comments as I go....... )

Finally, a great problem to solve! I really enjoy stuff like this.
Did a considerable amount of tinkering with the POD, but that was last
century. :-)
Mostly with the IBM PS/2 line of computers, and also clone boards. I don't
recall any Packard Bell experiences.

I'm not sure if I have a 486 PB in my 20 Packard Bell collection. I should
try to duplicate this problem if I do.


"Poster 60" wrote in message
...
Hello PB group,

I have an old 486 - PB Axcel 251 from 1995. I have made the full upgrades
for the modem,56K, and all the memory (64 ram, 512 L2cache,and 2 mb for
video ram)

THIS YOU MUST DOCUMENT! :-)
Fascinating. Does your 486 have a COAST slot, or cache DIPPS? I would like
to see pics of this, chip numbers, and the VRAM chip numbers also.


but can't for the processor. Its a DX-2 /66mhz chip, socket 3
type. I got the upgrade that the manual recommended, Pentium Overdrive 83
5V. and it was not compatible. When I looked it up on the internet, I
found
out I needed an interposer. Packard Bell said nothing about this in the
manual. I look at AMD processors and they had the same problem.


All the interposer does is disable one pin. If memory serves, it has to do
with write back cache, *I think*. You can simply bend that pin out of the
way if need be. Do a Google search, and you will find out which pin. I made
webpages about this, but that was many years ago.
Are you sure your POD is good?
I would remove the L2 cache and see what happens. On the IBM PS/2, the cache
caused a lot of problems with the POD. Look into your BIOS and see if you
can disable it, or change it from write back.
Are you sure your BIOS supports the POD? You may need to flash the BIOS, if
an update is available, and if you can find one.

Does the computer even boot to BIOS? Or do nothing? Very important.



I tried a DX 4 - 100 and changed the bus setting ,but that
didn't work either.

You don't need to change the bus setting. The DX2-66 and DX4100 are both
33MHz. The multplier is taken care of by the upgrade CPU also, if BIOS
supports.


I saw an old posting that said to use the DX4 - 100ODP
and I wouldn't have to bother with an interposer. I didn't realize there
were two types of DX-4 100, and I got the wrong one.


Yes. You want the 5V version.



I have looked on Ebay
and other places and can't find the right one - the ODP one. I'm thinking
they are all gone. Any ideas on this?


They show up all the time. Patience. :-)


I got this computer brand new in 1995 and since it was such
a useful tool at the time I decided to keep it as a working antique.



Sure, besides, this kind of tinkering is damn fun. I'll be thinking of
suggestions to make today, but time is limited now, gotta go to work. I'm
sure I'm forgetting something, or getting something wrong. Ben and others
will be along shortly to assist.

By the way, do you have a tower or desktop case ?

bobwatts


--
boBWatts®©
EartH
Watts Carburetion Service
Whizzbang Computers

I have to look through the collection of old 486-type parts I still have here,
mostly for old time's sake. I'll check what I have here and get back to you
tomorrow. Today has been a pretty long day... Ben Myers

On Mon, 3 Dec 2007 01:23:36 -0500, "Poster 60" wrote:

Hello PB group,

I have an old 486 - PB Axcel 251 from 1995. I have made the full upgrades
for the modem,56K, and all the memory (64 ram, 512 L2cache,and 2 mb for
video ram) but can't for the processor. Its a DX-2 /66mhz chip, socket 3
type. I got the upgrade that the manual recommended, Pentium Overdrive 83
5V. and it was not compatible. When I looked it up on the internet, I found
out I needed an interposer. Packard Bell said nothing about this in the
manual. I look at AMD processors and they had the same problem.
I tried a DX 4 - 100 and changed the bus setting ,but that
didn't work either. I saw an old posting that said to use the DX4 - 100ODP
and I wouldn't have to bother with an interposer. I didn't realize there
were two types of DX-4 100, and I got the wrong one. I have looked on Ebay
and other places and can't find the right one - the ODP one. I'm thinking
they are all gone. Any ideas on this?
I got this computer brand new in 1995 and since it was such
a useful tool at the time I decided to keep it as a working antique.

"Robert E. Watts" wrote in message
...
Hi 60 !



I have an old 486 - PB Axcel 251 from 1995. I have made the full
upgrades
for the modem,56K, and all the memory (64 ram, 512 L2cache,and 2 mb for
video ram)

THIS YOU MUST DOCUMENT! :-)
Fascinating. Does your 486 have a COAST slot, or cache DIPPS?

No, it only has 3 expansion slots, two being used already.
One is the original sound/modem card, with the 14.4 modem disabled and the
other is the new 56K sound fax modem. The third one is empty.

There is no mention of cache DIPPS in the manual.


I would like
to see pics of this, chip numbers, and the VRAM chip numbers also.

I'll get some pics for you.
The chip numbers are as follows:
The SRAM L2 cache chips(4) are 61C1024, ISSI brand. They are also
identifierd as 128k x 8 (20ns).
Two other chips were also necessary:
(1) 32k x 8 (15ns)
(1) 64k x 1 (15ns)

For the additinonal 1 mb video ram:
(2) 256 x 16 (70ns) ZIP DRAM chips.
I got those on Ebay. The seller sold them only in groups of 9, so I have 7
left over.


but can't for the processor. Its a DX-2 /66mhz chip, socket 3
type. I got the upgrade that the manual recommended, Pentium Overdrive
83
5V. and it was not compatible. When I looked it up on the internet, I
found
out I needed an interposer. Packard Bell said nothing about this in the
manual. I look at AMD processors and they had the same problem.


All the interposer does is disable one pin. If memory serves, it has to do
with write back cache, *I think*. You can simply bend that pin out of the
way if need be.

From what I saw on the internet, only one pin from the interposer would go
into the socket. The Overdrive pins
would be in the interposer.


Do a Google search, and you will find out which pin. I made
webpages about this, but that was many years ago.
Are you sure your POD is good?

As far as I know - yes.

I would remove the L2 cache and see what happens.

I'll give that a try.

On the IBM PS/2, the cache
caused a lot of problems with the POD. Look into your BIOS and see if you
can disable it, or change it from write back.

I'll check that.

Are you sure your BIOS supports the POD?

According to the PB manual, yes. It is either the OverDrive or the
PentiumOverDrive. What I got is the OverDrive - the P24T 83mhz.

You may need to flash the BIOS, if
an update is available, and if you can find one.

Does the computer even boot to BIOS? Or do nothing? Very important.

Yes, it boots to the BIOS.

By the way, do you have a tower or desktop case ?
This is a desktop case. The towers came later.

Poster 60

"Poster 60" wrote in message
...
Are you sure your BIOS supports the POD?

According to the PB manual, yes. It is either the OverDrive or the
PentiumOverDrive. What I got is the OverDrive - the P24T 83mhz.

Correction - It is a Pentium Overedrive P24T 83mhz.

Here is a link that tells the upgrades:

http://users.erols.com/chare/cpu_sock.htm#486socket

Poster 60

Hello 60

Did a little snipping.....


"Poster 60" wrote in message

Fascinating. Does your 486 have a COAST slot, or cache DIPPS?

No, it only has 3 expansion slots, two being used already.
One is the original sound/modem card, with the 14.4 modem disabled and the
other is the new 56K sound fax modem. The third one is empty.

There is no mention of cache DIPPS in the manual.



No. My question did not have to do with the expansion slots, I was referring
to how you installed your cache sram chips.


I would like
to see pics of this, chip numbers, and the VRAM chip numbers also.

I'll get some pics for you.
The chip numbers are as follows:
The SRAM L2 cache chips(4) are 61C1024, ISSI brand. They are also
identifierd as 128k x 8 (20ns).
Two other chips were also necessary:
(1) 32k x 8 (15ns)
(1) 64k x 1 (15ns)



If you have 4 128K cache chips, you only have 64k of cache sram, not 512K.
This should be revealed by watching the BIOS screen upon startup. This is
actually more like I expected, instead of having 512k of L2.

The other chips are tag sram. Rather intersesting that they don't match.

To get 512K of L2, you would have needed either 8 512k chips, or 4 1024k
chips.

Don't forget, it takes 8 bits to make a byte. :-)




For the additinonal 1 mb video ram:
(2) 256 x 16 (70ns) ZIP DRAM chips.
I got those on Ebay. The seller sold them only in groups of 9, so I have
7
left over.


From what I saw on the internet, only one pin from the interposer would go
into the socket. The Overdrive pins
would be in the interposer.


The interposer is a "socket looking like" device that fits between the CPU
and Socket 3 on the motherboard. All of the pins of the interposer go into
the socket.


I would remove the L2 cache and see what happens.

I'll give that a try.


Should be interesting.

bob

A little more info, because I lived through the "Pentium Ready" 486 systems,
mostly Gateways, selling a few hundred hand-assembled 486-like CPU upgrade kits
until some of the large companies figured it out. I also sold cache chips to
upgrade the cache memory, and a combo kit of CPU with cache chips, all with
illustrated installation guide, selling originally for $149 or $159 IIRC. Those
were the days when CPU upgrades actually provided some useful bang for the buck.

Intel created a real mess by designing its 83MHz Pentium OverDrive CPU with a
write-back external cache, rather than the write-through cache of the 486s. Most
of the 486 motherboards were likewise designed with a write-through cache,
causing the Pentium OverDrive to either hang or to run about as fast as a 6MHz
286. Gateway got hit with a class-action lawsuit for selling Pentium Ready 486s
that were not ready for a Pentium OverDrive chip, but that's another story.

Here are the basic practical CPU upgrade choices for a system with a 66MHz
80486-DX2:

1. 100MHz Intel 80486-DX4 OverDrive, operating at 5v
2. 133MHz AMD Am586 CPU, operating at 3.3v with supporting kit. This is a
486-workalike CPU with larger internal cache.
3. 83MHz Intel Pentium OverDrive with interposer to force CPU to operate with an
internal write-through cache. Intel finally relented and announced an
interposer for the Pentium OverDrive, but by then the damage had already been
done, very few interposers were ever made, and Socket 5 Pentium systems were
being sold in large volume.

In addition, the Intel 80486-DX4, non-OverDrive operating at 3.3v would work
with a suitable interposer to handle the voltage conversion from 5v to 3.3v.
However, interposers for 486 sockets were originally scarce as hen's teeth, so
they are now probably in the realm of mythology.

Also, if the motherboard supports a write-back cache, the Pentium OverDrive
would work without an interposer. However, NONE of the 486 write-back CPU
solutions will work with an Adaptec 1540-series or BusLogic 542 SCSI host
adapter. Interestingly, with the technology of the time, a write-back cache
was only 2-3% faster than write-through, so Intel engineers screwed up the
Pentium Overdrive big time with its write-back cache.

Evergreen and PowerLeap (I think) were two of companies that made 486 upgrade
kits in some volume.

If your PB 486 motherboard has a Zero Insertion Force (ZIF) socket, there is no
problem removing and installing CPUs. If it does not have a ZIF socket, you
need a little chip extraction tool.

Ray's very nice PB site on GeoCities and Velix' PB web site are now pretty
useless with many broken links, and no schematics or photos of PB 486
motherboards. So it is difficult to figure out exactly which model of board you
have there. PB sold 486 motherboard models 400, 401, 410, 420, 430, 440, 450
and 470. I'll guess that you have one of the later ones. Unfortunately,
"Axcel 251" is somewhat meaningless, because PB used all sorts of names and
models for its computers even tho there were relatively few motherboards used.
The model of the motherboard is what is most important... Ben Myers

On Mon, 3 Dec 2007 01:23:36 -0500, "Poster 60" wrote:

Hello PB group,

I have an old 486 - PB Axcel 251 from 1995. I have made the full upgrades
for the modem,56K, and all the memory (64 ram, 512 L2cache,and 2 mb for
video ram) but can't for the processor. Its a DX-2 /66mhz chip, socket 3
type. I got the upgrade that the manual recommended, Pentium Overdrive 83
5V. and it was not compatible. When I looked it up on the internet, I found
out I needed an interposer. Packard Bell said nothing about this in the
manual. I look at AMD processors and they had the same problem.
I tried a DX 4 - 100 and changed the bus setting ,but that
didn't work either. I saw an old posting that said to use the DX4 - 100ODP
and I wouldn't have to bother with an interposer. I didn't realize there
were two types of DX-4 100, and I got the wrong one. I have looked on Ebay
and other places and can't find the right one - the ODP one. I'm thinking
they are all gone. Any ideas on this?
I got this computer brand new in 1995 and since it was such
a useful tool at the time I decided to keep it as a working antique.

"Robert E. Watts" wrote in message
...


No. My question did not have to do with the expansion slots, I was
referring
to how you installed your cache sram chips.

They were just pressed into the motherboard carefully.
I had to bend the pins out just a bit on both sides so they would go in
straight without bending. I had to be extra careful because other pin holes
were available for smaller chips. I had to make sure the pins went into the
right holes. I could have either 128K cache or 512K cache.
I chose the 512K.




I would like
to see pics of this, chip numbers, and the VRAM chip numbers also.

I'll get some pics for you.
The chip numbers are as follows:
The SRAM L2 cache chips(4) are 61C1024, ISSI brand. They are also
identifierd as 128k x 8 (20ns).
Two other chips were also necessary:
(1) 32k x 8 (15ns)
(1) 64k x 1 (15ns)



If you have 4 128K cache chips, you only have 64k of cache sram, not 512K.

128 X 4 = 512


This should be revealed by watching the BIOS screen upon startup.

Correct, and is does show as 512K.

This is
actually more like I expected, instead of having 512k of L2.

The other chips are tag sram. Rather intersesting that they don't match.

To get 512K of L2, you would have needed either 8 512k chips, or 4 1024k
chips.

Right, I got 4 1024k chips. That is the manufacturer number.



Don't forget, it takes 8 bits to make a byte. :-)




For the additinonal 1 mb video ram:
(2) 256 x 16 (70ns) ZIP DRAM chips.
I got those on Ebay. The seller sold them only in groups of 9, so I
have
7
left over.


From what I saw on the internet, only one pin from the interposer would
go
into the socket. The Overdrive pins
would be in the interposer.


The interposer is a "socket looking like" device that fits between the CPU
and Socket 3 on the motherboard. All of the pins of the interposer go
into
the socket.


I would remove the L2 cache and see what happens.

I'll give that a try.

I disabled the cache from the BIOS but that didn't work.
The bootup was only partial. Here's how it read:

PB450m+ PNP Release 1.1
CPU= P24T 100mhz
640K System Ram Passed
64512 Extended Ram Passed
System BIOS Shadowed
Video BIOS Shadowed

This is where the bootup stopped.

Poster 60

"Ben Myers" wrote in message
...


If your PB 486 motherboard has a Zero Insertion Force (ZIF) socket,
there is no
problem removing and installing CPUs. If it does not have a ZIF socket,
you
need a little chip extraction tool.

Mine has the (ZIF) socket, so yes, it's easy to remove the CPU.

Ray's very nice PB site on GeoCities and Velix' PB web site are now pretty
useless with many broken links, and no schematics or photos of PB 486
motherboards. So it is difficult to figure out exactly which model of
board you
have there. PB sold 486 motherboard models 400, 401, 410, 420, 430, 440,
450
and 470. I'll guess that you have one of the later ones.

Mine is the 450 motherboard. As it boots up it says:
PB450M + PNP release 1.1A

The model of the motherboard is what is most important...

I agree.
Technology was changing very fast between 1995 and
1999. The 56k modems were selling new then for $100 - today you get one
for $20 or less. I got my second Packard Bell in May of 1999, the SYNERA
489 with Windows 98. I still have it also, but it is not being used for
now. That CPU is 333mhz. In the space of four years going from 66mhz to
333mhz is certainly big change.
Windows for Workgroups, (3.11) didn't have any firewalls available. That's
why I got the new one in 1999.

Poster 60