List of 486 motherboards to work well with the Pentium Overdrive (POD) in write-back mode

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Re: List of 486 motherboards to work well with the Pentium Overdrive (POD) in write-back mode

Postby BitWrangler » 2017-11-22 @ 02:27

There were 32 bit socket 4 systems also though, think those were gussied up 486 chipsets.
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Re: List of 486 motherboards to work well with the Pentium Overdrive (POD) in write-back mode

Postby Anonymous Coward » 2017-11-22 @ 02:41

Most of the early Pentiums had a 32-bit memory path, especially if we're talking consumer oriented products. I believe Compaq was a notable exception.
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Re: List of 486 motherboards to work well with the Pentium Overdrive (POD) in write-back mode

Postby feipoa » 2017-11-22 @ 03:48

You brought up a good point. It would be interesting to see what is the oldest 486 motherboard to work properly with the POD in WB mode.
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Re: List of 486 motherboards to work well with the Pentium Overdrive (POD) in write-back mode

Postby bbhaag » 2017-12-03 @ 04:25

Interesting thread. I have a DEC system running a POD83 with 11mb of ram and 128kb of L2 cache. I had to buy the sram from Mouser a couple years ago because the mainboard didn't have any installed. I have a service manual from 1996 stating the L2 cache runs in wb mode but I can not confirm this. I've run Cachechk7 but it does not report if the L2 cache ram is running in wb or wt.
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Re: List of 486 motherboards to work well with the Pentium Overdrive (POD) in write-back mode

Postby feipoa » 2017-12-03 @ 18:33

The objective of the thread is to eventually form a list of motherboards which work with the POD's L1 cache set in write-back mode, not the motherboard's L2 cache mode.
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Re: List of 486 motherboards to work well with the Pentium Overdrive (POD) in write-back mode

Postby bbhaag » 2017-12-05 @ 01:49

Unfortunately I do not believe I will be able to assist then. So far using the programs listed in this thread I have been unsuccessful in determining what mode the cpu cache is running in. Also the service manual I have does not detail this either.
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Re: List of 486 motherboards to work well with the Pentium Overdrive (POD) in write-back mode

Postby feipoa » 2017-12-05 @ 02:20

Could you attached a screenshot of what CTCM, CTCM7, cachechk7, and CHKCPU16 show?
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Re: List of 486 motherboards to work well with the Pentium Overdrive (POD) in write-back mode

Postby bbhaag » 2017-12-05 @ 03:25

feipoa wrote:Could you attached a screenshot of what CTCM, CTCM7, cachechk7, and CHKCPU16 show?

I can upload pics from ctcm, cachechk7, and chkcpu16. I do not believe they will assist you in your search though. It appears on my mainboard the cpu operates in write-through mode. I apologize for the substandard pictures. They were the best I could take with my inadequate camera.
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cachechk7.JPG
cachechk7
ctcm.JPG
ctcm
chkcpu16.JPG
chkcpu16
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Re: List of 486 motherboards to work well with the Pentium Overdrive (POD) in write-back mode

Postby feipoa » 2017-12-05 @ 03:32

bbhaag wrote: So far using the programs listed in this thread I have been unsuccessful in determining what mode the cpu cache is running in. Also the service manual I have does not detail this either.

The photos you provided indicate that your Pentium Overdrive is operating in Write-Through mode. I'm not sure why you said you were uanble to determine this in your previous message.
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Re: List of 486 motherboards to work well with the Pentium Overdrive (POD) in write-back mode

Postby bbhaag » 2017-12-05 @ 03:39

I must have been mistaken when I posted earlier. I apologize for my mistake.
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Re: List of 486 motherboards to work well with the Pentium Overdrive (POD) in write-back mode

Postby vetz » 2017-12-05 @ 07:27

I know the PC Chips M921 runs the POD in WB mod, same with the Asus VL/I-486SV2GX4 (does not work with SCSI VLB with DMA/busmastering with WB enabled).


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Re: List of 486 motherboards to work well with the Pentium Overdrive (POD) in write-back mode

Postby feipoa » 2017-12-05 @ 08:14

Vetz, which SCSI VLB adapter did you test with? I sort of recall a similar issue with an Adaptec 2842VL and was wondering if, perhaps, some adapters might allow for the POD-WB + SCSI VLB on the VL/I-486SV2GX4. Thus far, I think I was only able to get the Am5x86 and Intel DX4 running w/2842VL and WB L1.
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Re: List of 486 motherboards to work well with the Pentium Overdrive (POD) in write-back mode

Postby vetz » 2017-12-05 @ 11:31

I only own Adaptec SCSI VLB cards and I have the same results as you mention with regards to what works with WB L1. Been on the lookout for a Buslogic card for ages.
In other tests I've done, using VLB IDE gives better theoretical and practical performance throughput compared to SCSI VLB (when using comparable drives), especially if you look at sustained read/write speeds. If the harddrive can read/write in higher speeds than the SCSI-2 interface limit of 10 mb/s there is little point in going the SCSI route if it's for performance. Only reason would be if you had a good quiet period accurate SCSI drive you wanted to use, or just want to use SCSI since its more quirky :)
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Re: List of 486 motherboards to work well with the Pentium Overdrive (POD) in write-back mode

Postby feipoa » 2017-12-05 @ 18:05

What a blow to the SCSI ego. When you say VLB IDE, you are referring to PIO IDE, and not some DMA bus mastering IDE, right?

I also have only tested that Adaptec SCSI card, but what do you think about this DTC 3274 VLB SCSI card for working with L1:WB? https://www.ebay.ca/itm/DTC-3274-VLB-SC ... 2513213244 What drew my attention were those two SRAM chips on the card.
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Re: List of 486 motherboards to work well with the Pentium Overdrive (POD) in write-back mode

Postby vetz » 2017-12-06 @ 13:56

Yes, I'm talking about PIO MODE 4.

No idea if it'll work or not. Would be great if someone could test another card than Adaptec.
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Re: List of 486 motherboards to work well with the Pentium Overdrive (POD) in write-back mode

Postby alvaro84 » 2018-1-02 @ 07:14

Okay, I finally got my first test setup for this topic together (Nah, I was originally 'trying to pick the best Am5x86s but whatever).

So (post will be hopefully extended in the future):

Shuttle HOT-433 (ISA/PCI, UMC888x chipset): CPUCHK shows that the cache runs in WB mode.
Gigabyte GA-5486AL (ISA/PCI, ALI 1487/89 chipset): The same result, it's in WB mode too.
QDI V4P895 (ISA/VLB, OPTi 895 chipset): Works fine too.
MS-4138 (ISA/VLB, SiS 471 chipset): I couldn't test it. It didn't boot with the POD, not even at 63MHz, even though it should support it.

After 3/3 (working) boards reported WB mode I grew suspicious and looked made Speedsys graphs on them. All had breakdowns in the write/move speed after the L1 cache so I guess Chkcpu was right.

[Unfortunately none of my 3 PODs can stably run at 100MHz. Quake kills them all, it's a nice indicator.]
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