iMic
Member
Hi folks,
I'm reassembling a rather good condition Digital Equipment DECpc LPv+ at the moment. It was originally a 486 DX-33, but it's now running a DX2-66, which is about as far forward as I'll be going with the processor. Really the machine is meant to be a hobby system for DOS to low-level Windows 95 at the most, so it doesn't need to be absolutely maxed out.
I need to sort out the cache situation though. The system has 3x DIP-24 sockets for Cache Tag, and 8x DIP-28 for Cache. According to the hardware maintenance manual for the LPv+, the machine requires:
One example of a working board I saw used three Cypress Semiconductor CY7C166-15PC 15ns chips for Tag, and eight Cypress CY7C199-20PC 20ns chips for Cache. This seems like a safe bet, since it's proven that this configuration and part works in this board, but I'd like some input from those more knowledgeable before I commit to ordering them.
Is 15ns Tag / 20ns Cache ideal for a 486 DX2-66 on a 33MHz bus? Should the chips be quicker, or is there no benefit in this configuration and substituting a full set of 20 or 25ns chips (which are sometimes more readily available and a bit cheaper) would also suffice?
I should add that the ICs don't need to be Cypress - Winbond, ISSI, Mosel-Vitelic, Motorola, etc works as well. But I've only been able to find part numbers for Cypress and Motorola in the DIP-24 16K x 4 ICs, and only Cypress, Winbond and Mosel-Vitelic for the 32K x 8 DIP-28's. Since I have Cypress part numbers for both, I figured purely for "lid-off aesthetics" I'd go for a matched set.
I'm reassembling a rather good condition Digital Equipment DECpc LPv+ at the moment. It was originally a 486 DX-33, but it's now running a DX2-66, which is about as far forward as I'll be going with the processor. Really the machine is meant to be a hobby system for DOS to low-level Windows 95 at the most, so it doesn't need to be absolutely maxed out.
I need to sort out the cache situation though. The system has 3x DIP-24 sockets for Cache Tag, and 8x DIP-28 for Cache. According to the hardware maintenance manual for the LPv+, the machine requires:
- four or eight 32KB x 8 cache SRAM chips
- three 16KB x 4 cache tag SRAM chips
One example of a working board I saw used three Cypress Semiconductor CY7C166-15PC 15ns chips for Tag, and eight Cypress CY7C199-20PC 20ns chips for Cache. This seems like a safe bet, since it's proven that this configuration and part works in this board, but I'd like some input from those more knowledgeable before I commit to ordering them.
Is 15ns Tag / 20ns Cache ideal for a 486 DX2-66 on a 33MHz bus? Should the chips be quicker, or is there no benefit in this configuration and substituting a full set of 20 or 25ns chips (which are sometimes more readily available and a bit cheaper) would also suffice?
I should add that the ICs don't need to be Cypress - Winbond, ISSI, Mosel-Vitelic, Motorola, etc works as well. But I've only been able to find part numbers for Cypress and Motorola in the DIP-24 16K x 4 ICs, and only Cypress, Winbond and Mosel-Vitelic for the 32K x 8 DIP-28's. Since I have Cypress part numbers for both, I figured purely for "lid-off aesthetics" I'd go for a matched set.