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First post, by jasa1063

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I have a CH-386-33A/40A motherboard with an Opti 82C391 chipset. The BIOS lacks any settings for memory timings. Is there a DOS configuration utility that exists to do this?

Reply 2 of 9, by jasa1063

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maxtherabbit wrote on 2021-11-27, 16:35:

I don't know if it's supported offhand, but check out CTCHIP34

The Opti 82C391 is supported in the list of configuration files in CTCHIP34 and there are settings for read and write wait states. I will give this a try and see how it goes.

Thanks for the heads up!

Reply 3 of 9, by GigAHerZ

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Chipset datasheet for M321 (PC Chips) [Found chipset! OPTi 82C391]

I had quite a trouble to get to know what chipset this board has, but found it out - it's the same you care about.

As you can read from the thread, there's MR BIOS available for your chipset. It has some memory timing settings available too. 😉
Before finding out, what chipset it was, i used AMISETUP to manually toggle bits in bios to tune the board.

"640K ought to be enough for anybody." - And i intend to get every last bit out of it even after loading every damn driver!

Reply 4 of 9, by jasa1063

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GigAHerZ wrote on 2021-11-27, 17:15:
Chipset datasheet for M321 (PC Chips) [Found chipset! OPTi 82C391] […]
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Chipset datasheet for M321 (PC Chips) [Found chipset! OPTi 82C391]

I had quite a trouble to get to know what chipset this board has, but found it out - it's the same you care about.

As you can read from the thread, there's MR BIOS available for your chipset. It has some memory timing settings available too. 😉
Before finding out, what chipset it was, i used AMISETUP to manually toggle bits in bios to tune the board.

Another option and much appreciated!

Reply 5 of 9, by jasa1063

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CTCHIP34 does work on my CT-386-33A/40A motherboard. The BIOS default was CAS 4 for memory reads and CAS 3 for memory writes. Slow refresh was not enabled, but hidden refresh was. The best I could get was CAS 3 for both memory reades and writes and enable slow refresh. I am not sure if slow refresh and hidden refresh are mutually exclusive. Here are the results running Speedsys 4.78.

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    Results using default BIOS settings
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  • SSTIMG02.jpg
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    Results are running CTCHIP34
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Reply 6 of 9, by mkarcher

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jasa1063 wrote on 2021-11-28, 15:57:

I am not sure if slow refresh and hidden refresh are mutually exclusive.

They are not mutually exclusive. Slow refresh is about how often the RAM gets refreshed. Usually "slow refresh" means that three of four refresh cycles are skipped. Most standard PC RAM is not specified for slow refresh, so slow refresh could cause data corruption on certain access patterns especially if the chips are quite warm.

Hidden refresh on the other hand is about the way in which refresh is performed. Hidden refresh is called that way because refreshing happens at least partly during the time at which a read cycle is still transmitting data from the RAM to the chipset, so it happens in parallel to a read and thus blocks RAM access for less time.

Reply 7 of 9, by jasa1063

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mkarcher wrote on 2021-11-28, 16:52:
jasa1063 wrote on 2021-11-28, 15:57:

I am not sure if slow refresh and hidden refresh are mutually exclusive.

They are not mutually exclusive. Slow refresh is about how often the RAM gets refreshed. Usually "slow refresh" means that three of four refresh cycles are skipped. Most standard PC RAM is not specified for slow refresh, so slow refresh could cause data corruption on certain access patterns especially if the chips are quite warm.

Hidden refresh on the other hand is about the way in which refresh is performed. Hidden refresh is called that way because refreshing happens at least partly during the time at which a read cycle is still transmitting data from the RAM to the chipset, so it happens in parallel to a read and thus blocks RAM access for less time.

Thanks for the clarification!

Reply 8 of 9, by GigAHerZ

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NB! Don't trust CTCHIP, when it says something is enabled or disabled - it's buggy as hell, even showing different values depending on your display mode (the "M" key).

Read the bits themselves and refer to documentation. Don't trust CTCHIP's explanations/descriptions.

"640K ought to be enough for anybody." - And i intend to get every last bit out of it even after loading every damn driver!

Reply 9 of 9, by jasa1063

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GigAHerZ wrote on 2021-11-29, 08:37:

NB! Don't trust CTCHIP, when it says something is enabled or disabled - it's buggy as hell, even showing different values depending on your display mode (the "M" key).

Read the bits themselves and refer to documentation. Don't trust CTCHIP's explanations/descriptions.

I did some more research and I am now using the AMISETUP DOS utility. The actual values for CAS Read/Write were both 1 not 4 and 3 as being reported by CTCHIP34. Thanks for the heads up on CTCHIP34!