1) Your graphics card does have 1 MB RAM and not 256 MB or kB.
2) You need 8 standard DIL 20 256k x 4 DRAM modules with a latency of 70ns or lower.

I'm surprised any VLB cards have less than 1mb ram. Yes I would upgrade as 256k would highly limit the resolution supported.

Are you sure it is 256k?

mwdmeyer wrote on 2023-01-13, 01:28:

Are you sure it is 256k?

It is definitely 1MB. Each of those chips is 256kx4. 8x256kx4 = 8192 kilobits = 8 megabits = 1 megabyte

Cool makes sense.

I would only upgrade from 1mb then if.

A) You want a higher supported resolution (windows)
B) The chipset supports memory interleaving (not sure if it does)

afair memory upgrade will only enable two interlaced resolutions on Cirrus Logic vlb chips

Yes no benefits.

2nd MB would only enable support of 1024x768 with 64k colours instead of 256 and 1280x1024 with 16 colours. However, both with unusable interlaced refresh rates (due to slow RAMDAC) which look ugly on CRT and rarely work with LCD screens. So there is no point.

Often memory sockets on these cheap cards were not for expansion but as alternative RAM options (so that they can fit whatever chips they could source cheapest without redesigning the PCB), so it won't work if you add more. Note also the solder pads on top of the CPU. You can't really tell without docs/ close inspection where to fit the memory expansion.

So save the hassle.

mpe wrote on 2023-01-13, 08:59:

2nd MB would only enable support of 1024x768 with 64k colours instead of 256 and 1280x1024 with 16 colours. However, both with unusable interlaced refresh rates (due to slow RAMDAC) which look ugly on CRT and rarely work with LCD screens. So there is no point.

[...]

So save the hassle.

I agree with that. In theory, that extra memory can be used for "offscreen surfaces" (as DirectX calls it), or for higher virtual screen size with hardware-assisted panning. I'm not aware of real-world applications that actually use this capability on Cirrus cards, though.

mpe wrote on 2023-01-13, 08:59:

Often memory sockets on these cheap cards were not for expansion but as alternative RAM options (so that they can fit whatever chips they could source cheapest without redesigning the PCB), so it won't work if you add more. Note also the solder pads on top of the CPU. You can't really tell without docs/ close inspection where to fit the memory expansion.

And while this is generally true, in case of this card, I am very confident that the 8 DIL-20 sockets are indeed meant for a second MByte of video RAM. You need to populate all eight of them anyway, as the Cirrus chip needs 32 bit memory interface for sensible performance (I don't remember whether it can work in a degraded "16-bit memory mode" with just 512kB, but that configuration would be awful). Furthermore, the option for a first bank of DIL-20 chips is clearly visible overlaying the soldered SOIC20/26 chips, so if the first MByte were to be populated with DIL-20 chips, other these solder pads would be used for that.

The one thing you would really need to measure are the soldering pads next to the Cirrus chip, which are meant for SOJ40 256K x 16 chips. Most likely, they are also meant for the first bank, as an alternative to the x4 chips that are installed, but I wouldn't bet my life on it. The design of that card makes a lot of sense in that you get the two SMD options (8x SOIC20/26 or 2x SOJ40) only for the first bank, which is populated by the manufacturer, but the pointless upgrade (that will only be performed by a low amount of customers, and the manufacturer doesn't care about the price and availability of those upgrade chips) is limited to the chip type the customer is most likely to install correctly (i.e. DIP).

Interlaced mode is not always unusable. I lived with interlaced 1024x768 87Hz 16bit for many years as my monitor couldn't handle more than 56Hz at 800x600 (unusable) and other hardware had priority. Interlaced 87Hz was far better than 56Hz non-interlaced. I would upgrade video memory to 2MB in this case and use 1024x768 87Hz 16bit.

As mkarcher says, additional memory can be used for offscreen objects, virtual resolution, triple buffering etc. I don't know how many games/applications took advantage of that, but in vesa modes (especially 2.0 lfb modes) its trivial to do, so I'm surprised more games didn't optionally take advantage of 512kb/1024/2048 vga memory.

Thanks everyone. I am glad that it has 1 MB. Seller insisted that it only had 256k.