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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 black ZX Spectrum photographed against white at an angle, its gray rubber keys printed with several commands each and a rainbow flash across the bottom right corner.

A rubber-keyed ZX Spectrum. Each key carries a whole BASIC keyword, which is how a 16 KiB ROM was typed at.

ccwoodcock · CC BY 2.0 · Wikimedia Commons

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

Europe

Component Role Count Clock Capacity
Zilog Z80A Main CPU 1 3.5 MHz Nominal clock —
ZX Spectrum ULA GPU 1 14 MHz 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

ZX Spectrum 48K: system figures

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.
Clock frequency gpu provisional 14 MHz Confirmed Vendor-rated Nominal clock Stated by the vendor This is the ULA master clock used for video timing. It is not a modern GPU execution 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.
3 documented absences
ZX Spectrum 48K: system figures: documented absences
Metric Value Evidence Basis Method Source
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
Zilog Z80A: documented absences
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.
ZX Spectrum 48K RAM

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.
ZX Spectrum ROM

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.

Sources