Home computer
ZX Spectrum 48K
A Z80A home computer with Sinclair BASIC in ROM and a ULA that drives the display. Each key carries a whole BASIC keyword, so a program is typed in rather than spelled out.
- Manufacturer
- Sinclair Research
- Released
- April 1982
- Region
- United Kingdom
- Record status
- provisional
A rubber-keyed ZX Spectrum. Each key carries a whole BASIC keyword, which is how a 16 KiB ROM was typed at.
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About this machine
Sinclair pushed almost everything outside the processor into a single custom chip, which is how the machine reached a price no rival matched. That chip also pauses the processor while it reads video memory, and the resulting contention is why one part of memory runs slower than the rest.
Configuration
PAL 48K
| Component | Role | Count | Clock | Capacity |
|---|---|---|---|---|
| Zilog Z80A | Main CPU | 1 | 3.5 MHz Nominal clock | — |
| ZX Spectrum ULA | GPU | 1 | unknown Nominal clock | — |
| ZX Spectrum 48K RAM | System memory | 1 | — | 48 KiB shared |
| ZX Spectrum ROM Read-only Sinclair BASIC ROM. | System memory | 1 | — | 16 KiB shared |
Figures for the whole machine
provisional A figure marked provisional is recorded but not accepted: its evidence is unsettled. It may rely on one source, an unconfirmed announcement, or a digit read from a damaged scan. The reason appears under the figure. The catalog shows the figure but never uses it in a multiplier. How records are judged.
| Metric | Value | Evidence | Basis | Method | Source |
|---|---|---|---|---|---|
| Clock frequency cpu provisional | 3.5 MHz | Confirmed | Vendor-rated | Nominal clock Stated by the vendor Sinclair's technical data names the Z80A's nominal clock. | |
| Memory capacity whole-system provisional | 48 KiB | Confirmed | Vendor-rated | Design capacity Stated by the vendor This is the fitted writable RAM capacity, not RAM plus ROM. |
4 documented absences
| Metric | Value | Evidence | Basis | Method | Source |
|---|---|---|---|---|---|
| Clock frequency gpu provisional | unknown The cited oscillator drives video timing; its frequency is not an execution-clock figure for comparison with graphics processors. | Not stated | Vendor-rated | Nominal clock Stated by the vendor The service manual gives the ULA's external clock for video timing, not a comparable graphics execution clock. | |
| Memory bandwidth memory provisional | unknown The source describes RAM access arbitration but provides no transfer-rate figure. | Not stated | Vendor-rated | Theoretical peak Stated by the vendor The service manual describes the ULA's priority over RAM access, but gives no memory transfer-rate figure from which bandwidth can be stated. | |
| Sustained FP40 rate whole-system provisional | unknown A Sinclair BASIC result requires a named reproducible benchmark before it can be published. | Not stated | Measured | Benchmark run Published independently | |
| Rated power consumption whole-system provisional | unknown The source supplies no whole-system power rating. | Not stated | Vendor-rated | Rated power Stated by the vendor The service manual describes the external supply and on-board regulation, but gives no whole-system power rating. |
Figures for its components
1 documented absence
| Metric | Value | Evidence | Basis | Method | Source |
|---|---|---|---|---|---|
| Peak FP32 rate cpu provisional | not applicable The Z80A contains no floating-point hardware. | Not stated | Vendor-rated | Theoretical peak Stated by the vendor Provisional record for zx-spectrum-z80a:peak-fp32-rate: the cited primary manual is registered, but its page-level transcription and independent review are still pending. |
provisional A figure marked provisional is recorded but not accepted: its evidence is unsettled. It may rely on one source, an unconfirmed announcement, or a digit read from a damaged scan. The reason appears under the figure. The catalog shows the figure but never uses it in a multiplier. How records are judged.
| Metric | Value | Evidence | Basis | Method | Source |
|---|---|---|---|---|---|
| Memory capacity memory provisional | 48 KiB | Confirmed | Vendor-rated | Design capacity Stated by the vendor Sinclair's service manual specifies the dynamic-RAM configuration. |
provisional A figure marked provisional is recorded but not accepted: its evidence is unsettled. It may rely on one source, an unconfirmed announcement, or a digit read from a damaged scan. The reason appears under the figure. The catalog shows the figure but never uses it in a multiplier. How records are judged.
| Metric | Value | Evidence | Basis | Method | Source |
|---|---|---|---|---|---|
| Memory capacity memory provisional | 16 KiB | Confirmed | Vendor-rated | Design capacity Stated by the vendor The service manual identifies the lower address region as ROM. |
What the museum label says
The Science Museum Group holds a 48K Spectrum with its power supply and a Horizon Software Starter Pack cassette, catalogued as object 1985-195 and dated 1982 to 1985.
The curatorial note attached to it states what the machine was for. Clive Sinclair introduced the ZX Spectrum in August 1982, meaning it as an upgraded ZX81 that could compete with the color graphics of the recently introduced Atari, Commodore and Acorn computers.
The note ends with an assessment: the Spectrum was Sinclair Research’s most significant commercial success, and it is what gave the company market dominance in the UK in the early 1980s.