A quick question about installing a DX4!

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A quick question about installing a DX4!

Postby Yuuker » 2018-1-24 @ 20:30

Couldn't find an answer so i thought i'd double check.

Is there any harm or performance degradation with using a Intel DX4 with write-back cache on a motherboard that doesn't support it? Found out i have one of those models, although it doesn't seem like my DataExpert EXP4044 has any option for toggling write-back cache, neither in the bios or jumpers (only jumpers for L2 write back/through toggling).
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Re: A quick question about installing a DX4!

Postby gerwin » 2018-1-24 @ 21:02

Intel DX4 with write-back cache support '&EW': These can do write-trough mode as well. So no worries.
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Re: A quick question about installing a DX4!

Postby Anonymous Coward » 2018-1-25 @ 01:22

If you use configure a DX4 for writeback in a system that doesn't support it, the system will simply crash.
Thankfully most CPUs that support writeback are set to writet hrough by default.
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Re: A quick question about installing a DX4!

Postby Ampera » 2018-1-25 @ 03:30

My EXP4045 has support for Write-back, but I believe it's a BIOS setting.
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Re: A quick question about installing a DX4!

Postby jheronimus » 2018-1-25 @ 08:53

Anonymous Coward wrote:Thankfully most CPUs that support writeback are set to writet hrough by default.


The CPU itself has a setting for writeback/writethrough? How do you change that setting? I thought it's only a motherboard/BIOS thing.
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Re: A quick question about installing a DX4!

Postby gerwin » 2018-1-25 @ 14:58

In this pinout table pin B13 works as a WT/WB selector.
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Re: A quick question about installing a DX4!

Postby jheronimus » 2018-1-25 @ 19:21

gerwin wrote:In this pinout table pin B13 works as a WT/WB selector.


Yes, but the only way to interact with that pin is by changing motherboard jumpers/BIOS settings, no? It's not like, say, changing Cyrix 5x86 options through software.
Socket 7: Pentium 166; 64MB RAM; Matrox Millenium+Voodoo 1; AWE32 PnP w/28MB + GUS PnP Pro w/8MB
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Re: A quick question about installing a DX4!

Postby gerwin » 2018-1-25 @ 21:18

Jumpers/BIOS, yes I think so, don't know about any related CPU registers on the intel 486.
Note that Write-Back did not entirely cooperate with my only 486 VLB system. Not yet at least. So I never benchmarked the supposed benefit.
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Re: A quick question about installing a DX4!

Postby Yuuker » 2018-2-06 @ 02:09

Sorry to bump but i didn't figure this quick related follow up question warranted its own thread.

I got the DX4, set the junpers. No boot. Got the lights on the keyboard, but no video.
Re seated it a couple times and even tried swapping back to my DX2 and its jumper configuration (which worked)

I'm theorizing my motherboard doesn't support write-back, but i might be wrong.

Statson doesn't seem to list any jumper for write-back, nor does the bios have anything.
http://stason.org/TULARC/pc/motherboard ... P4044.html

Maybe i'm missing something :blah: Hopefully the chip itself isn't dead.
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Re: A quick question about installing a DX4!

Postby jheronimus » 2018-2-06 @ 07:38

JP34 seems to set L2 cache to writeback according to the stason link you’ve posted
Socket 7: Pentium 166; 64MB RAM; Matrox Millenium+Voodoo 1; AWE32 PnP w/28MB + GUS PnP Pro w/8MB
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Re: A quick question about installing a DX4!

Postby Yuuker » 2018-2-06 @ 08:10

jheronimus wrote:JP34 seems to set L2 cache to writeback according to the stason link you’ve posted

Would that do anything for the cpu though? Unless the board is looking for both L1 and L2 states to match.
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Re: A quick question about installing a DX4!

Postby jheronimus » 2018-2-06 @ 09:55

Yuuker wrote:
jheronimus wrote:JP34 seems to set L2 cache to writeback according to the stason link you’ve posted

Would that do anything for the cpu though? Unless the board is looking for both L1 and L2 states to match.


I don't think I've ever seen a board that has separate jumpers for L1 and L2 cache. Then again, both my VLB boards (AOpen VI15G QDI Opti 895) have both cache jumpers and a cache setting in BIOS
Socket 7: Pentium 166; 64MB RAM; Matrox Millenium+Voodoo 1; AWE32 PnP w/28MB + GUS PnP Pro w/8MB
Slot 1: Pentium III 500; 384MB RAM; Voodoo 5 5500 AGP; AWE64 Value w/8MB + Diamond Monster Sound MX300 + SoundBlaster Live!
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Re: A quick question about installing a DX4!

Postby Yuuker » 2018-2-06 @ 17:43

jheronimus wrote:
Yuuker wrote:
jheronimus wrote:JP34 seems to set L2 cache to writeback according to the stason link you’ve posted

Would that do anything for the cpu though? Unless the board is looking for both L1 and L2 states to match.


I don't think I've ever seen a board that has separate jumpers for L1 and L2 cache. Then again, both my VLB boards (AOpen VI15G QDI Opti 895) have both cache jumpers Cand a cache setting in BIOS


Nope, no dice. Changing that jumper made no diffrence. I even tried disabling internal cpu cache via the bios to see if maybe that would bypass any board trouble but to no luck.

Very unsure weather the cpu is dead or not, i have a board with proper L1-writeback support on the way but it won't be here for some time :blah:
Either that, or my VLB Video card isn't play nice with a dx4.
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