S3 86C805-P memory upgrade? \ VOGONS

S3 86C805-P memory upgrade?

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First post, by Erwin_Br

Posted on 2023-10-30, 11:27

Erwin_Br Offline

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Posts: 24
Joined: 2021-04-23, 11:01

I have a S3 86C805-P lying around that I would like to use for a new DOS build.

Its 8 memory DIP slots are all empty and I was considering to look for an upgrade. The card supports up to 2MB, with 70ns DRAM. My questions are:

1. Are there specific requirements I should be looking for? Right now I'm searching to find 8 "DRAM DIP20 256 70ns". Will any module do that I'll find, or do I need to be more specific? - I am very new to this 😀
2. Is it worth it for this card? Will it have a noticeable gain over the default configuration? (1MB)

Thanks!

Erwin

Reply 1 of 1, by mkarcher

Posted on 2023-10-30, 22:29

mkarcher Offline

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Posts: 2670
Joined: 2019-01-19, 16:29
Location: Germany

You don't need anything more specific. 8 chips of DIP20 FPM RAM 256k x 4 will do. Getting 256k x 4 in DIP20 in any other memory kind than FPM (fast page mode) is very rare, so not paying attention to "FPM" is likely no problem.

As far as I know, there will be no noticable gain, because the S3 805 is in a similar ballpark as the CL-GD542x chips regarding memory bandwidth. You can find multiple threads on VOGONs on the pointlessness of upgrading Cirrus cards, and this also applies to the S3 805: The chip is unable to read more than 1MB 60 times a second, so every video mode requiring more than 1MB RAM can not be displayed at 60Hz, so will likely be interlaced, which is useless with most modern TFT displays.

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