Robhalfordfan wrote on 2023-02-08, 21:15:

ok i should be safe use buy use the nec chips without any problem and will the wires make the ce on pin 30 on the nec chip, pull low or high and thought it was ground pin the wire is going on the 68882 which the trace is going to NC pin (maybe i am looking at wrong datasheet)

You look at the right datasheet, but with the wrong perspective. The socket pinout is usually depicted for looking into the holes of the socket. If you look at the back of the board, you get a mirror image. Pin A1 (the Vcc pin at coordinate A1, not the address line A1) is at the corner with the golden "Y". The bodge wire is at the inner pin in the corner clockwise from the Y looking at the chip markings, or counter-clockwise looking at the solder connections. If you look carefully, you can see pin A1 having a square pad on the solder side. As the data sheet is not for the solder side, going clockwise from A1 locates you at the corner with K1 (which happens to carry the signal A1), but the bodge wire is at the inner edge of that corner, that's pin H3, carrying the signal A0, as I wrote in my previous post. There is a trace from H3 to F1, which is /SIZE.

mkarcher wrote on 2023-02-09, 00:35:

Robhalfordfan wrote on 2023-02-08, 21:15:

ok i should be safe use buy use the nec chips without any problem and will the wires make the ce on pin 30 on the nec chip, pull low or high and thought it was ground pin the wire is going on the 68882 which the trace is going to NC pin (maybe i am looking at wrong datasheet)

You look at the right datasheet, but with the wrong perspective. The socket pinout is usually depicted for looking into the holes of the socket. If you look at the back of the board, you get a mirror image. Pin A1 (the Vcc pin at coordinate A1, not the address line A1) is at the corner with the golden "Y". The bodge wire is at the inner pin in the corner clockwise from the Y looking at the chip markings, or counter-clockwise looking at the solder connections. If you look carefully, you can see pin A1 having a square pad on the solder side. As the data sheet is not for the solder side, going clockwise from A1 locates you at the corner with K1 (which happens to carry the signal A1), but the bodge wire is at the inner edge of that corner, that's pin H3, carrying the signal A0, as I wrote in my previous post. There is a trace from H3 to F1, which is /SIZE.

oh ok, yeah, i was looking at it from wrong perspective as you said, thanks for the clarification and as you said the nec chips should be safe to use and what will the bodge wires make the CE2 pin on the nec pins do, if anything

Robhalfordfan wrote on 2023-02-09, 09:19:

oh ok, yeah, i was looking at it from wrong perspective as you said, thanks for the clarification and as you said the nec chips should be safe to use and what will the bodge wires make the CE2 pin on the nec pins do, if anything

The old chip in you accelerator card only respond to read and write cycles, if pin 22 is low. The NEC chips only respond to read and write requests if pin 22 is low and pin 30 is high. The bodge wire connects to a pin of the 68882 which must be connected to +5V (A0), so we can be sure that the bodge wire ensures that pin 30 is always high. If pin 30 is always high, the only other thing the NEC chip cares about is that pin 22 must be low for the chip to respond, which is exactly the same behaviour as the chip you currently have in that baord.

mkarcher wrote on 2023-02-09, 18:32:

Robhalfordfan wrote on 2023-02-09, 09:19:

oh ok, yeah, i was looking at it from wrong perspective as you said, thanks for the clarification and as you said the nec chips should be safe to use and what will the bodge wires make the CE2 pin on the nec pins do, if anything

The old chip in you accelerator card only respond to read and write cycles, if pin 22 is low. The NEC chips only respond to read and write requests if pin 22 is low and pin 30 is high. The bodge wire connects to a pin of the 68882 which must be connected to +5V (A0), so we can be sure that the bodge wire ensures that pin 30 is always high. If pin 30 is always high, the only other thing the NEC chip cares about is that pin 22 must be low for the chip to respond, which is exactly the same behaviour as the chip you currently have in that baord.

ok, i am guessing that a yes

Robhalfordfan wrote on 2023-02-09, 18:48:

ok, i am guessing that a yes

Yes, the NEC chip will work as drop-in replacement. No further modifications required.

mkarcher wrote on 2023-02-09, 18:53:

Robhalfordfan wrote on 2023-02-09, 18:48:

ok, i am guessing that a yes

Yes, the NEC chip will work as drop-in replacement. No further modifications required.

that's good to look the person i got this from maybe thought that and future proof it in a way

and thank you for every one for the help and also all the clarification will let you all know when the chip has arrived and worked

Great! Hope for that SRAM search helped for you.

Cheers,

hello all, i bought the nec sram chips and arrived today, took the old chips and replace with new ones and the it passed it ram test and added the main amiga memory and works no issues 😀

Bravo!!!

Have fun.

Cheers, Jason

thank you jason 😀