question about vic's ram chips

Overdoc · Post by **Overdoc** » Thu Nov 13, 2008 10:03 am

Just a quick question:

There are 5 ram chips in the VIC-20 (CR model):

UE1, UD2 and UD2: 1kb x 4 bit 2114 ram
U14 & U15: 2kb x 8 6116 ram (or clones)

I think UE1 is color ram, while UD2 and UE2 together form the first 1KB of ram starting at $0000 to $0400, each providing 4 bits.
And both rams at U14 amd U15 are forming the other 4KB of the 5kb ram, starting at $1000 to $2000.

Did I get this right ?

eslapion · Post by **eslapion** » Sun Nov 16, 2008 6:17 pm

You did!

adric22 · Post by **adric22** » Mon Nov 17, 2008 5:26 pm

what a strange configuration. Was that one of those "Well, we already have a bunch of these chips laying around.." decisions?

6502dude · Post by **6502dude** » Mon Nov 17, 2008 5:50 pm

adric22 wrote:what a strange configuration. Was that one of those "Well, we already have a bunch of these chips laying around.." decisions?

Yes.

Also, keep in mind ram chips were very expensive in early 1980s

Post by **Jeff-20** » Mon Nov 17, 2008 9:48 pm

Frankenstein's monster.

eslapion · Post by **eslapion** » Mon Nov 17, 2008 10:43 pm

adric22 wrote:what a strange configuration. Was that one of those "Well, we already have a bunch of these chips laying around.." decisions?

I don't remember where but I vaguely remember reading that the first VICs had eleven 2114 chips because Commodore had huge amounts of these in stock either because of PET computers or calculators.

I suppose as the stocks of these chips ran out, they wanted to use the larger capacity 2116 because it would reduce the footprint of chips and they used that opportunity to make the VIC use the same pinout/voltages as the C64 PSU.

Since a single 2116 has the capacity of four 2114 and the config of the memory of the VIC lends well to using a pair of 2116 to represent the standard 4K of RAM between $1000-$1FFF, eight 2114 got replaced by two 2116. This made the VIC cheaper to manufacture and reduced its power consumption.

Something similar happened with the C64 which originally used eight 4164 DRAM chips which were replaced in the later boards no. 250466 and 250469 with two 41464. This too allowed a reduction in size of the main board and a lower power consumption.