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RAM Test

Cambridge Computer wrote a BBC BASIC program to test the RAM. Unless the memory is good the Z88 will become unstable, the FAIL indicator may appear in the top right-hand corner of the display or inconsistent results will occur when checking the size of the RAM with (<> CARD). For example, you may have a 512K Ram card in your Z88 but (<> CARD) reports that you only have 128K. Failure of the RAM falls in the following categories.

• Mechanical failure - due to the contacts being dirty or from a dry soldered joint
• Unsuitable memory chip - if a different chip is used it may not have the identical specification.

Running the BASIC program while `tapping' the RAM pack may identify a mechanical failure. Finding other errors can be difficult.

The other sort of memory failure is where certain bits of memory suffer amnesia when you are not reading or writing to the memory.

This is like when you are just storing files in the RAM.

This fault can be found with any program, (zCheck, Zip, Unzip (Z88 Forever) or SqueeZ~88 (Rakewell)) that uses checksums on files. To use it you should:-

1. Run the program initially so that the checksums of the files are calculated. If you are using SqueeZ~88 or Zip, squeeze/Zip a load of big files.
2. Turn off the Z88 and leave it alone for about three to five days.
3. Re-run the program to see if the checksums of the files are different or unsqueeze/Unzip all the files again. If they are, then the RAM where the file was stored is faulty.

The following BBC BASIC program tests 32K, 128K 512K and 1MB Ram packs.

It is what is called a destructive Ram Test which means that all the data that is stored on the RAM will be destroyed.

Download the 4 files zipped, (original instructions, two .CLI files (which do the same thing) and the memory test software from here, and then transfer them to your Z88 with a transfer program.

. Image Added

There are two ways you can use this program.

1. Just running the BBC BASIC program (Ramcard.bas)

1. Before using the program you should save the program to EPROM as "RAMTEST.BAS" and write the following BOOT.CLI to use with it.

#F
|EF
RAMTEST.BAS~E~E
#B
CHAIN
"RAMTEST.BAS"~E

to do the memory test, do the following:-

1. Back-up all your files.
2. Take out the RAM pack.
3. Put in the EPROM with the two files BOOT.CLI and RAMTEST.BAS in it.
4. Do a Hard Reset.
5. When you get the Command line "Size of card to test? (in KBytes, Eg. 32, 128 etc.)" type in the number of K the ram card is.
6. Put the Ram card in Slot 1.
7. Press the ENTER key until you get the "Testing . . . " message.
8. When the test is finished,
9. Remove the EPROM pack and
10. Do another Hard Reset.

Supply Voltage Min

2.7

Input High Voltage

0.7 x VCC min

to VCC+0.3

2.2 to VCC+0.3

2.4 to VCC+0.3

2.4 to VCC+0.5

2.2 to VCC + 0.5 V

Input Low Voltage

0.5 to 0.8

-0.5 to 0.8

- 0.2 to 0.6

- 0.2 to 0.6

Output High Voltage

2.4 min

Output Low Voltage

0.4 max

0.4 max

0.4  max

Standby Power 

3.5 to 50

VCC for Data Retention

Chip Enable Access Time tACE 

Output Disable to Output in High-Z tOHZ

18 max 

Output Hold from Address Change tOH

Write Cycle Time tWC

Address Valid to End of Write tAW

35 min 

Chip Enable to End of Write tCW 

35 min

Address Set-up Time tAS 

Write Pulse Width tWP 

Write Recovery Time tWR 

Data to Write Time Overlap tDW 

Data Hold from End of Write Time tDH 

Data Setup to Write End

25 min

Output Active from End of Write tOW 

Write to Output in High-Z tWHZ